Method and apparatus for measuring rowing technique

Abstract

The present disclosure relates to a system for providing real-time performance feedback on a rowing machine, the rowing machine comprising: a load cell 1 coupled to a support rail; a seat 5 slidably coupled to the support rail for supporting a rower; a handle 3 coupled to the load cell and arranged to move relative to the load cell by a pulling action on the handle; and a footrest rack 4 coupled to the support rail and arranged to receive a pushing action on the footrest rack, the system comprising: a first sensor 13 configured to measure a first parameter indicative of the pulling action on the handle; a second sensor 11 configured to measure a second parameter indicative of the pushing action received by the footrest rack; and a data processing unit (DPU) configured to determine a relationship between the pulling action on the handle and the pushing action received by the footrest rack based on the first parameter and the second parameter.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method and associated apparatus for providing a quantitative measure of a rower's technique. BACKGROUND

[0002] Glossary of terms used in the specification:

[0003] “Load cell”: the portion of the rowing machine that consumes the power generated by the rower

[0004] “Pull phase”: the portion of the rowing stroke where the rower is applying force and speed in the forward direction (i.e. away from the load cell) so that the handle is doing work in the load cell

[0005] “Recovery phase”: the portion of the rowing stroke where the rower is moving the handle in the reverse direction towards the load cell in preparation for the next pull phase, with negligible force applied on the handle

[0006] “Grip”: the start of the pull phase

[0007] “Finish”: the end of the pull phase

[0008] “Foot stretcher”: the area where the rower’s feet contact the rowing machine or boat

[0009] “World coordinate system”: a fixed inertial frame of reference used to measure movement

[0010] “CM”: centre of mass

[0011] “ergo”: the generic abbreviation for rowing machines or rowing ergometers

[0012] “DPU”: data processing unit

[0013] In competitive rowing sports, not only is a significant amount of time spent developing the strength and fitness of the rower, but also their technique in applying their available strength and fitness to move the boat efficiently to achieve the maximum possible speed over the target distance. Typically, the rower’s technique is improved through a combination of observation and imitation of other rowers more skilled in the technique, and through coaching, where a coach provides the rower with verbal qualitative feedback on how they can improve their movement to enhance the movement capabilities of their boat. This verbal form of feedback can be provided when using a rowing machine on land, or when in a real boat on water. For team boats, the overall efficiency is also highly dependent on the degree of synchronisation of the movements of the individual rowers with their teammates.

[0014] A significant problem with the qualitative nature of verbal feedback is that successful improvement in the technique of the rower is highly dependent on how accurately the coach can quantify and visually explain the areas in which the rower's movement efficiency can be improved, and then translate this subjective explanation into a form of words that the rower can understand and apply to their body movements.

[0015] Coaches often use video of the rower to support their analysis, but this is generally only possible after the rowing session has finished. Coaches can also provide further verbal instructions after the session, but the delay in this feedback makes it more difficult for the rower to absorb the information given, as they are less likely to accurately associate what they hear and see afterwards with their body movements (i.e. proprioception) as they perceived them during the session. The process is therefore fraught with misunderstandings, and often requires many sessions (if at all) to achieve significant improvement.

[0016] It is well known in the research of sports science that immediate (also known as "real-time"), quantitative and impartial feedback allows athletes to modify their movements through an experimental process or "trial and error", and will generally result in their skill level improving more rapidly, particularly when reinforced through verbal instruction. This direct, quantitative and objective feedback can alleviate the frustration that can arise between coaches and athletes when verbal feedback alone is ineffective.

[0017] There are also often psychological detrimental effects due to "fear of failure" or suffering from the lack of recognition in the coach's subjective verbal feedback, and sometimes the tone of voice used by the coach can exacerbate this problem.

[0018] Another danger of subjective verbal instruction is that, in the instruction session, the coach can want to try to correct more than one error at a time, and in fact fail to make real progress on any of them; the rower can then feel overwhelmed with information and become negative during the session, feeling that there are too many errors and that progress cannot be made in correcting them.

[0019] Rowing machines are often used as part of a rower's training program. They typically measure the work done by the rower during the pull phase of a rowing stroke via a moveable handle coupled to a flywheel, which provides resistance to movement of the handle as the flywheel rotates, thereby attempting to replicate the resistance experienced by the rower's handle as they move their oar through water in a real boat. Flywheel rotational resistance is often achieved using air brake vanes, but can also be achieved electrically via some form of generator and load coupled to the flywheel. There are also variants that provide handle resistance via linear actuation elements such as pistons. In the following description, the term "load unit" is used to encompass any such device that provides resistance to movement of the handle.

[0020] A significant advantage of training rowers on rowing machines is that the training can be conducted in a controlled environment, thus not subject to the highly variable conditions typically experienced in a real boat on water. The machine also provides a quantitative measure of the power output of the rower in real time under controlled conditions, thus the machine is a good way to objectively and consistently compare fitness levels between rowers.

[0021] However, a significant problem with using rowing machines as an indicator of a rower's ability is that typically only the total power output delivered by the rower through the handle of the machine is measured, and not how effectively that power can be translated into moving a real boat on water. It is not uncommon for a rower to achieve good results in a rowing machine test, but not be able to replicate that performance in a real boat due to one or more flaws in their rowing technique.

[0022] It is also common for rowers to adopt a particular type of movement that produces good power measurements on a rowing machine, but which in fact is not conducive to moving a real boat efficiently, and because a rower's training time is relatively large spent on a rowing machine rather than rowing a real boat, these bad habits can become ingrained through repetition.

[0023] The fact that conventional rowing machines simply measure the total power delivered by the rower through the handle of the machine also encourages rowers to consciously or subconsciously focus on using their arms to move the handle, when in fact a larger proportion of their power output is generated through the effective use of their legs and back during the drive phase, with the arms primarily used to couple that power to the handle for a significant proportion of the drive. Thus, rowers are encouraged to focus on using their legs and back powerfully in the movement, which tends to improve their performance when propelling a real boat on water. SUMMARY

[0024] One aspect of the present technology provides a system for providing real-time performance feedback on a rowing machine, the rowing machine comprising: a load unit coupled to a support rail; a seat slidably coupled to the support rail for supporting a rower; a handle coupled to the load unit and arranged to move relative to the load unit by a pulling action on the handle; and a footrest rack coupled to the support rail and arranged to receive a pushing action on the footrest rack, the system comprising: a first sensor configured to measure a first parameter indicative of the pulling action on the handle; a second sensor configured to measure a second parameter indicative of the pushing action received by the footrest rack; and a data processing unit (DPU) configured to determine a relationship between the pulling action on the handle and the pushing action received by the footrest rack based on the first parameter and the second parameter.

[0025] In some embodiments, the handle can be coupled to the load unit by means of a first chain or a first cable, and wherein the first sensor is coupled to the chain or the cable and configured to measure a tension applied to the first chain or the first cable when pulling the handle as the first parameter to determine the pulling force.

[0026] In some embodiments, the support rail can be mounted on a plurality of rollers arranged to run along a set of guide rails, wherein the second sensor can be coupled to at least one roller of the plurality of rollers and configured to measure a speed of movement of the rowing machine relative to the floor as the second parameter, and wherein the DPU can be configured to use the speed of movement of the rowing machine to derive the pushing force caused by the pushing action received by the footrest frame.

[0027] In some embodiments, the footrest frame can be rigidly coupled to the load unit and the load unit is slidably coupled to the support rail by a plurality of rollers, wherein the second sensor can be coupled to at least one roller of the plurality of rollers and configured to measure a speed of movement of the load unit relative to the support rail as the second parameter, and wherein the DPU can be configured to use the speed of movement of the load unit to derive the pushing force caused by the pushing action received by the footrest frame.

[0028] In some embodiments, the footrest frame can be slidably coupled to the support rail by a plurality of rollers and coupled to the load unit by means of a second chain or a second cable, wherein the footrest frame can be arranged to move along the support rail relative to the load unit, wherein the second sensor can be coupled to at least one roller of the plurality of rollers and configured to measure a speed of movement of the footrest frame relative to the support rail as the second parameter.

[0029] In some embodiments, the system can further include a third sensor coupled to the second chain or the second cable and configured to measure a tension applied to the second chain or the second cable when pushing the footrest frame, and wherein the DPU can be configured to determine the pushing action received by the footrest frame as the tension applied to the second chain or the second cable.

[0030] In some embodiments, the load unit can include a flywheel, and the first chain or the first cable can be coupled to the flywheel by a cogwheel or a pulley, and the system can further include a fourth sensor disposed at the cogwheel or the pulley and configured to measure a speed of movement of the handle relative to the load unit.

[0031] In some embodiments, the system can further include a fifth sensor coupled to the seat and configured to measure a speed of movement of the seat relative to the support rail, wherein the DPU can be configured to determine a relative speed of the handle relative to the seat using the speed of movement of the handle relative to the load unit and the speed of movement of the seat relative to the support rail.

[0032] In some embodiments, the DPU can be configured to determine the relationship as a ratio between the pulling action on the handle and the pushing action received by the foot cradle based on the first parameter and the second parameter.

[0033] In some embodiments, the system can further include a communication connection configured to connect the DPU to one or more sensors provided on one or more other rowing machines.

[0034] In some embodiments, the system can further include a communication connection configured to connect the DPU to a corresponding DPU provided on another rowing machine.

[0035] In some embodiments, the rowing machine can be one of a plurality of rowing machines connected through respective communication connections, and wherein the DPU is configured to determine a time profile of the relationship between the pulling action on the handle and the pushing action received by the foot cradle.

[0036] In some embodiments, the rowing machine can be one of a plurality of rowing machines mechanically linked together.

[0037] In some embodiments, the system can further include a display, wherein the DPU is configured to perform the determination in real time and to display results of the determination in real time.

[0038] Another aspect of the present technology provides a computer-implemented method of providing real-time performance feedback on a rowing machine, the rowing machine comprising: a load unit coupled to a support rail; a seat slidably coupled to the support rail for supporting a rower; a handle coupled to the load unit and arranged to move relative to the load unit by a pulling action on the handle; and a foot cradle coupled to the support rail and arranged to receive a pushing action on the foot cradle, the method comprising: measuring a first parameter indicative of the pulling action on the handle; measuring a second parameter indicative of the pushing action received by the foot cradle; and determining in real-time a relationship between the pulling action on the handle and the pushing action received by the foot cradle based on the first parameter and the second parameter.

[0039] In some embodiments, the handle may be coupled to the load unit via a first chain or a first cable, and measuring the first parameter may include measuring the tension T applied to the first chain or the first cable when the handle is pulled. h To determine the pulling force.

[0040] In some implementations, the support rail may be mounted on a plurality of rollers arranged to slide along a set of guide rails, and measuring the second parameter may include measuring the rowing machine's speed of movement V relative to the floor. ew The method may also include using the rowing machine's speed V according to the following equation. ew To derive the thrust F caused by the pushing action received by the pedal frame. f :F f =(T h –M e *dV ew / dt), where M e *dV ew / dt represents the force acting on the rowing machine.

[0041] In some embodiments, the method may further include using the pushing force F received by the pedal frame according to the following equation. f And the rowing machine's speed V ew To determine the power P of the pushing action transmitted to the pedal frame. fw :P fw =-F f *V ew .

[0042] In some embodiments, the method may further include: measuring the movement speed V of the handle relative to the load unit. hw ; and the tension T applied to the first chain or the first cable when the handle is pulled, according to the following equation. h and the moving speed V of the handle hw To determine the power P transmitted to the handle for the pulling action. hw :P hw =T h *V hw .

[0043] In some embodiments, the method may further include basing the method on the mass M of the rower according to the following equation. r The mass M of the rowing machine e And the rowing machine's speed V relative to the floor. ew To determine the center-of-mass velocity V of the rower. rCMw V rCMw =-(M e / M r )*Vew .

[0044] In some embodiments, the footrest frame is rigidly coupled to the load unit and the load unit is slidably coupled to the support rail by a plurality of rollers, and measuring the second parameter can comprise measuring a speed of movement V luw of the load unit relative to the support rail, and the method can further comprise using the measured movement of the load unit to derive a pushing force F f .

[0045] In some embodiments, the method can further comprise determining a power P luw of the pushing action imparted to the footrest frame using the pushing force Ff received by the footrest frame and the speed of movement V fw of the load unit according to the equation: fw P = -F f * V luw .

[0046] In some embodiments, the footrest frame is slidably coupled to the support rail by a plurality of rollers and is coupled to the load unit by means of the second chain or the second cable, wherein the footrest frame is arranged to move along the support rail relative to the load unit, wherein measuring the second parameter can comprise measuring a speed of movement V fw .

[0047] In some embodiments, the method can further comprise measuring a tension T f applied to the second chain or the second cable when the footrest frame is pushed, and determining the pushing action received by the footrest frame as the tension applied to the second chain or the second cable.

[0048] In some embodiments, the method can further comprise measuring a power P fw of the pushing action imparted to the footrest frame using the pushing force T f received by the footrest frame and the speed V fw of the footrest frame according to the equation: fw P = -T f * V fw .

[0049] In some embodiments, the method can further comprise measuring a speed of movement V sw of the seat relative to a world coordinate system, and determining a relative speed V h-s of the handle relative to the seat using the speed of movement V hw of the handle and the speed of movement V sw of the seat according to the equation: h-s V = Vhw - V sw ; and determining a numerical indicator as real-time feedback of the technique of the rower based on the relative speed V h-s

[0050] In some embodiments, the method can further include comparing the numerical indicator to a reference corresponding to an optimal stroke curve.

[0051] In some embodiments, the method can further include measuring a speed of movement of the seat relative to the support rail; determining a speed of the rower's feet based on the speed of movement of the rowing machine, the speed of movement of the load cell, or the speed of movement of the foot cradle; and using the speed of movement of the seat and the speed of the rower's feet to determine a relative speed of the seat relative to the speed of the rower's feet to provide an indication of the technique of the rower.

[0052] In some embodiments, the method can further include measuring a duration of time from when the seat is in a first position to when a force is applied to the load by the handle or the foot cradle, wherein the first position can be a position where the seat is closest to the load cell along the support rail.

[0053] In some embodiments, the rowing machine can be one or more rowing machines connected through respective communication connections, and the method can further include determining a time profile of the relationship between the pulling action on the handle and the pushing action received by the foot cradle.

[0054] In some embodiments, the method can further include determining a ratio between the pulling action on the handle and the pushing action received by the foot cradle based on the first parameter and the second parameter.

[0055] Yet another aspect of the present technology provides a non-transitory computer readable medium comprising machine readable code which, when executed by a processor, causes the processor to perform a method as described above.

[0056] Still another aspect of the present technology provides an apparatus for measuring tension in a reciprocating chain, the apparatus comprising: a coupling base configured to couple the apparatus to the chain; one or more pawls disposed on the coupling base, each pawl configured to engage a link in the chain; and one or more deflection sensing elements mounted on the coupling base and configured to generate an output signal indicative of a deflection force exerted on the coupling base when the chain is under tension. BRIEF DESCRIPTION OF DRAWINGS

[0057] Embodiments of the present technology will now be described, by way of example only, with reference to the attached drawings, in which:​

[0058] Figure 1 A simplified schematic showing the basic features of a typical rowing machine fixed to the floor, with the load cell in the form of a rotating flywheel with air braking vanes.

[0059] Figure 2 A position of the specified sensors attached to a typical rowing machine of Figure 1 , where the rowing machine is now mounted on a sliding base so that the rowing machine is movable relative to the floor or “world coordinate system”. The mentioned main velocities and forces are also shown.

[0060] Figure 3 A position of the specified sensors attached to a rowing machine with an integrated sliding load cell, showing the main velocities and forces considered.

[0061] Figure 4 A position of the specified sensors attached to a rowing machine, where the load cell is fixed in the world coordinate system and the footrest rack is moving relative to the machine, again showing the main forces and velocities.

[0062] Figure 5 A basic feature of a sensor that can measure the tension in the chain connecting the handle to the load cell is shown.

[0063] Figure 6 A chain tension sensor of Figure 5 mounted on the handle chain of a rowing machine is shown.

[0064] Figure 7 A schematic representation of a data processing unit (DPU), an index selection unit and a display device is shown, where the DPU is connected to sensors from one or more rowing machines equipped with sensors according to an embodiment. DETAILED DESCRIPTION

[0065] Some examples of specific rowing technique errors will now be outlined to show aspects of the rower’s movement for which the present technology can provide real-time, quantitative feedback.

[0066] One error is that the rower uses their legs to push their feet against the load cell at the beginning of the pull phase without engaging their “core” muscles to effectively couple the generated force through the handle to the load cell, colloquially known as “shooting the slide” or “bum shoving”. This results in the rowing machine’s seat, and indirectly also the rower’s center of mass, moving faster than the handle at the beginning of the pull phase.

[0067] In contrast to "seat moving too fast on the pull", another error is the rower using their back muscles too hard to open their body angle at the catch, causing the handle to move faster than their centre of mass initially. This is sometimes referred to as "lifting at the catch".

[0068] To address the above problems and limitations, the present technology provides a method of providing real-time quantitative feedback to a rower of selected indicators of specific aspects of the rower's movement that are believed to be important to rowing efficiency, and associated apparatus.

[0069] The feedback generated by the present technology is provided during each stroke or at the completion of each stroke, so that the rower can modify their movement pattern in real-time in an effort to improve the reading of the selected indicators. A coach can facilitate this process by making oral suggestions to the rower while they are actively rowing on the machine, and the immediate feedback obtained when the rower and coach find a movement form that improves the indicators makes it easier for them to retain the "feel" of the improved movement from the "muscle memory".

[0070] A coach or rower can use the software provided with the apparatus to select one specific indicator for display, and then spend as much time as required to improve that indicator before proceeding to another, where the coach or rower does not attempt to proceed to correct another error until the first indicator has been quantitatively improved.

[0071] The quantitative nature of the indicators displayed also allows for the objective, rather than subjective, comparison of skill levels of different rowers. This removes any bias in the coach's recommendations in rower evaluation and team selection.

[0072] Furthermore, the quantitative nature of the indicators allows for the data to be easily recorded and reviewed to assess the progress of a rower over time from the start of their involvement in a training program.

[0073] The indicators can be derived in a way that quantifies and reports on skill levels, not just total power output as is currently presented by traditional rowing machines. This allows for the identification of less powerful rowers as potentially faster rowers when pitted against more powerful opponents in a real boat, a feature that is particularly useful when selecting rowers for inclusion in a team boat.

[0074] The present invention includes some form of electronic data processing unit or DPU that can simultaneously acquire data from one or more rowing machines equipped with the sensors described herein. This allows for real-time feedback of selected metrics that quantify how well multiple rowers are synchronizing their movements. The overall speed of the team boat is highly dependent on this level of synchronization, and using this device to provide simultaneous real-time feedback from more than one rower will allow less skilled rowers to modify their movements in real time to try to match the movements of more skilled rowers.

[0075] A dataset of "optimal" stroke curves for a specific rowing pattern can also be pre-programmed into the DPU, allowing all team members to modify their movements in real time during training sessions to strive towards that optimal value. Optimal stroke curves can be obtained from individual rowers whom the coach believes best represent the desired rowing pattern, or alternatively, optimal stroke curves can be derived from a mathematical model.

[0076] exist Figure 1 In this rowing machine, the load unit 1 consists of a flywheel 15 and a chain or cable 2. The flywheel has air brake blades 16. The chain or cable typically connects the rowing machine's handle 3 to the flywheel of the load unit via gears or pulleys. The rower 20 sits on a seat 5, which can move freely horizontally along the rowing machine's seat support track 6 on rollers 8. The rowing machine is fixed relative to a world coordinate system 7.

[0077] exist Figure 2 middle, Figure 1 The rower and rowing machine are shown mounted on rollers 9, which are typically restricted to running on rails, allowing the rowing machine to move freely only in a horizontal direction relative to the world coordinate system 7. A sensor 12, connected to any of the rollers 9, measures the combined movement of the rowing machine and rower relative to the world coordinate system 7. A second sensor 10 is linked to a gear or pulley and measures the movement of the handle relative to the load unit, which connects the handle chain or cable to the flywheel of the load unit. A third sensor 11 is linked to a roller on the sliding seat 8 to measure the movement of the seat relative to the seat support rail 6. A force sensor 13 is mounted to the handle chain or cable to measure the tension in the chain or cable.

[0078] The center of gravity of the rower is Figure 2 The center of mass is shown as being located at 14, although this center of mass moves slightly relative to the stroker's body as the stroker's joint angle changes.

[0079] exist Figure 2 In this context, the velocity measured relative to world coordinate system 7 is represented by the subscript "w", therefore V hw It's the controller speed, V ew It's the speed of ergo, VrCMw is the speed of the CM of the rower, and V sw is the speed of the seat, all measured in the world coordinate frame.

[0080] “T h ” is the tension measured by the handle chain or cable sensor. F f is the reaction force between the footrest frame and the rower’s feet.

[0081] The measured value V 12 is the velocity of the load cell and the ergo relative to the world coordinate frame, i.e.:

[0082] V ew = V 12 (Equation 1)

[0083] The measured value V 10 is the velocity of the handle relative to the ergo, and so expressed in world coordinate frame velocity as:

[0084] V 10 = V hw – V ew

[0085] Thus:

[0086] V hw = V 10 + V 12 (Equation 2)

[0087] Similarly, consider the measured value V 11 from sensor 11:

[0088] V 11 = V sw – V ew

[0089] Thus:

[0090] V sw = V 11 + V 12 (Equation 3)

[0091] If the mass of the rower is M r and the mass of the ergo is M e , then the CM of the entire system (i.e. the rower and ergo as a whole) can be assumed to remain stationary in the world coordinate frame, since there are no external forces acting on this entire system if small frictional forces at the rollers and air resistance are ignored.

[0092] Applying Newton’s second law to the forces acting on the ergo, ignoring the frictional forces at the seat rollers 8:

[0093] M e *dV ew / dt = (T h -F f )

[0094] Re-arranged to:

[0095] F f = (T h -M e *dV ew / dt) (Equation 4)

[0096] Similarly, considering only the horizontal components and applying conservation of momentum:

[0097] M r *V rCMw + M e *V ew = 0

[0098] And re-arranged to:

[0099] V rCMw = - (M e / M r )* V ew (Equation 5)

[0100] The relative velocity of the handle with respect to the seat V h-s gives an indication of how well the rower is connecting the force generated by their legs with the handle, where:

[0101] V h-s = V hw - V sw (Equation 6)

[0102] If the rower tends to "slide the seat too fast while pulling" at the start of the pull phase, V h-s is negative at this point, and the DPU can show a numerical indication of the magnitude of this "slippage" early in the pull phase. Alternatively, a range of levels can be pre-programmed into the DPU so that it can present the feedback in other forms, for example, red, amber and green lights or audible tones, or possibly a vibration generator in the seat or handle of the rowing machine to provide haptic feedback. Feedback can also be provided via innocuous electrical stimulation of the skin.

[0103] Another useful indicator that can be derived from the sensors is the relative proportion of the power P f generated by the rower via their legs on the foot stretcher and the power P h delivered to the ergometer via the handle (or work, if the power is integrated over time). Calculated in the world coordinate system, these power values are:

[0104] P fw = -Ff * (V f -V ew ) (Equation 7)

[0105] P hw = Th * (V h -V hw ) (Equation 8)

[0106] The DPU can measure the P hw / P fw ratio throughout the pull phase and again use the various feedback methods mentioned previously to provide feedback on how well this ratio matches the best stored curve measured against time or handle position.

[0107] It was found in experimentation that measuring the relative power ratio in the CM frame of the rower gives a good indication of whether the rower is exhibiting the previously described "slide moving too fast during the pull" or "catching up" errors.

[0108] P frCM = -Ff * (V ew -V rCMw ) (Equation 9)

[0109] P hrCM = Th * (V hw -V rCMw ) (Equation 10)

[0110] As mentioned previously, the DPU can report the P frCM / P hrCM ratio to the rower and coach in real time.

[0111] Another set of metrics that can be easily derived from the system is the absolute and relative amount of impulse (i.e. change in momentum) that the rower is transferring through the handle and foot stretcher.

[0112] It was found in experimentation that during the initial pull phase, a portion of the energy from the rower's leg drive is transferred to their CM in the world frame, and then as the rower increases the force and velocity of the handle near the middle and end of the pull phase, this "stored" kinetic energy is transferred to the load cell via the handle. This effect can also be quantified in terms of momentum exchange.

[0113] The exchange of energy and momentum between the rower's mass velocity and the machine described above is also understood to occur on a real boat, where as the rower's velocity relative to the water decreases, this exchange causes the water velocity of the boat to speed up near the end of the stroke. It is therefore advantageous to be able to quantify this effect in real time so that the rower can improve how well they can utilize the effect on the rowing machine and then use their body feel gained on the machine to replicate the effect on a real boat.

[0114] Other metrics that can be readily obtained from the system are the time profiles of force, power and impulse generated at the handle, and also the corresponding profiles transmitted through the foot stretcher (see, for example, equations 4, 7 and 9 for foot force and power derivation).

[0115] In existing research, it has been found that certain time profiles are indicative of effective rowing technique, so the DPU can be programmed with these exemplary profiles so that the rower can again use real-time quantitative indications of matching quality to strive to match their stroke profile to the desired profile. For this type of feedback, it can be advantageous to use some form of graphical display that shows the rower's stroke profile overlaid with the reference desired profile.

[0116] It is also very useful to see how selected metrics deteriorate as the rower fatigues during a training session and / or as the rowing intensity increases in real time, as this is an important characteristic of skilled rowers, i.e. their ability to maintain their skill level throughout the duration of a race.

[0117] In the case where multiple systems are connected to the DPU, as shown in Figure 7 the DPU can provide real-time metrics for the quality and stability of the time profiles between multiple rowers in a team training session. One such measure is how close the rowers can get to each other in their timing of the start of their respective pull phases; another is how close the rowers can get to each other in their respective times to peak force generated at the handle and foot stretcher, and yet another is how close the rowers can get to each other in their times to reach a particular percentage of the impulse being transmitted to the system by either or both the handle, foot stretcher.

[0118] To facilitate the team coordination training described above, the rowing machines can be mechanically linked together so that each rower can feel the movement of the linked components. However, this means that the individual foot force of each rower cannot simply be derived from the acceleration of the linked rowing machine components (i.e. through equation 4), but other metrics can still be derived from the individual measurements of handle force and velocity of each rower, and their seat and CM velocities.

[0119] Another advantageous feature applicable to single or multiple systems is that the DPU can measure and continuously report in real time the stroke length that each rower is achieving during the duration of the session. Stroke length is the distance travelled by the handle relative to the load cell, and for a given body type of rower, stroke length is a measure of the flexibility of the rower. It will be appreciated that in competitive rowing, it is important to maintain a consistent stroke length throughout a race, so it is very useful to have real-time feedback of stroke length on the rowing machine during a training session, which enables the rower and coach to see if their stroke length is decreasing due to fatigue or due to an increase in rowing intensity.

[0120] When multiple rowing machines are mechanically linked together, it is possible to measure whether individuals are able to reproduce the typical stroke length they can achieve when using the device in isolation, as it is common for rowers to row the shortest stroke length in a combined system, whether in the form of linked rowing machines or an actual team boat.

[0121] It is also useful to be able to monitor the total work delivered by the rower to the load cell in each stroke, i.e. the integral of the handle force and handle displacement over each complete stroke, and this metric can be calculated without reference to foot force, and is therefore possible for mechanically linked rowing machines.

[0122] Yet another advantage of the system is that, for individual or linked rowing machines equipped in accordance with embodiments of the application, the point in the stroke at which the rower reaches a certain percentage of their total handle impulse can be accurately related to the position of the handle relative to the machine, and this information can be used effectively to set the rigging of a team boat so that each rower exerts an output that is optimal for their body type.

[0123] For individual or linked rowing machines, the system is also able to quantify how the rower moves over the rowing machine during the backstroke phase of the stroke, and this information can also reveal certain technique flaws. One such flaw is for the rower to approach the grip position on the machine too quickly and uncontrolled, i.e. “rushing the slide”. The speed of the seat relative to the machine, i.e. the seat speed sensor output V 11 , and the CM velocity of the rower in the world coordinate system V rCMw , can be used to produce a feedback metric to quantify the extent of this error.

[0124] The force on the footrest rack as the rower approaches the grip position can also be used to derive a metric of how well the rower is controlling their movement during the backstroke phase of the stroke on an individual rowing machine.

[0125] Another set of useful metrics that can be fed back in real time relate to how the rower moves the handle during the backstroke phase of the stroke. The speed of the handle relative to the rower, i.e. (V hw – V rCMw , can be measured and compared to an exemplary curve that the coach wishes the team to reproduce. Typically, the coach will provide verbal guidance by observing how the rower moves their handle relative to their teammates when rowing back, so the system can provide a more accurate, quantitative measure of this in real time.

[0126] Sometimes, highly skilled and well-coordinated rowers will adopt a rowing style in which they intentionally accelerate their CM speed near the catch, which allows them to exploit the elasticity of their tendons and the neuromuscular “stretch reflex” response to “spring off’ the foot stretcher more explosively. This allows the rower to minimize the time they spend at the catch position before the start of the drive phase, as this position is typically where the real boat deceleration is the most.

[0127] The above technique can be practiced using appropriate feedback metrics computed by the DPU individually and during team training sessions. Success in this technique depends on the accurate application of handle force soon after reaching the catch position, so, for example, the system can report a timing quality metric to indicate the duration of time spent between an individual reaching the catch position and starting the drive phase, and it can provide another metric indicating how well these time periods overlap between two or more individuals being monitored simultaneously.

[0128] Figure 3 The relevant sensors attached to the rowing ergometer are shown, which has a sliding load cell 1 that can move horizontally on support rails 6 on rollers 18 together with the seat 5. A rotary sensor 17 is connected to one of the rollers 18 to measure the movement of the load cell relative to the support rails, but as previously mentioned, in alternative embodiments this movement can be measured by means other than a rotary sensor.

[0129] It will be readily apparent to those of ordinary skill in the art that the previously discussed parameters can be derived from the sensors indicated on this type of rowing ergometer; for example, M e and V ew are replaced by the mass M lu and velocity V luw of the load cell instead of the mass and velocity of the entire rowing ergometer.

[0130] Figure 4 The relevant sensors attached to the rowing ergometer are shown, which has a load cell 1 rigidly coupled to support rails 6, which in turn are fixed to the floor, i.e., the world coordinate frame 7. The foot stretcher 4 can move horizontally along the support rails 6 on rollers 18 together with the seat 5. Here, the CM of the rower remains relatively stationary with respect to the world coordinate frame, and the mechanism allows both the handle and the foot stretcher to move independently to deliver power to the load cell. The seat movement sensor 11 measures the relatively small movement of the seat on the support rails 6 so that the movement of the CM of the rower can be accurately measured in the world coordinate frame. Sensor 21 measures the movement of the foot stretcher relative to the support rails, and sensor 19 measures the tension T f in the chain or cable 22 connecting the sliding foot stretcher to the load cell.

[0131] In this embodiment, the tension T f The foot force is measured directly, rather than being derived from the Figure 2 and Figure 3 foot force from equation 4 of the rowing machine shown in

[0132] In the previously described embodiments of the technology, the sensor measuring the speed is a rotary sensor, but in other embodiments the relative movement can be measured by a non-rotary sensor, for example a magnetic or optical linear encoder, or an ultrasonic or laser position sensor.

[0133] In other embodiments, the tension in the chain or cable coupling the handle to the load cell can be measured in the load cell itself, for example by measuring the angular acceleration of a flywheel, or with a force sensing load cell in the bearing support of the load cell flywheel or in any idler wheel of the chain or cable. Similarly, the tension in the chain or cable coupling the moving footrests of the rowing machine of Figure 4 to the load cell can be measured by such alternative means.

[0134] A significant advantage of the technology is that the horizontal foot force F f has been present in the prior art, but it is difficult to measure the horizontal foot force component accurately without errors due to the direction and point at which the force is applied from the rower's foot to the sensor. Since the foot is typically strapped to the footrest, it is allowed to apply a torque to the intervening sensor, so twisting the foot on the sensor can also introduce errors. Such sensors are therefore often both complex and bulky and expensive to manufacture if good accuracy and reliability are to be provided. Typically a sensor is required for each foot, which further increases the cost and complexity.

[0135] Figure 5 A perspective view of a chain tension sensor suitable for use in the technology is shown, and Figure 6 how the roller chain 30 is attached to the tension sensor: by twisting the chain and hooking over a pawl 32 of a coupling member (or base) 31 so that the chain tension is transmitted through the coupling member. The connection member will typically be made of steel, and when tension is applied through the chain, the member will flex approximately linearly in proportion to the amount of tension applied, provided the tension does not approach the elastic limit of the material from which the member is made.

[0136] Preferably, a pair of flexure sensing elements 33 are mounted on opposite sides of the coupling member 31 to cause the flexure signals generated when configured in a bridge circuit to be doubled, and also to provide temperature compensation for thermal expansion of the substrate material, as is well known in the art. The flexure sensors are typically strain gauges, although other devices such as piezoelectric elements can also be used to generate an electrical signal proportional to the degree of flexure experienced by the coupling member.

[0137] An electronic circuit 34 connected to the flexure sensors via wires 35 amplifies their output signals and transmits them to the DPU, possibly via a flexible coiled cable attached to the rowing machine so that the handle is free to move, or alternatively by wireless means such as radio, infrared or ultrasonic transmission. The amplified analog signals from the flexure elements can be signals conditioned by the electronic circuit to improve linearity and correct for offset, and the signals can also be digitized before transmission to the DPU.

[0138] A significant advantage of the illustrated chain tension sensor is that it can be easily fitted to and removed from a standard rowing machine chain without the need to remove the handle or disassemble the chain, as would be required if a conventional load cell were employed. The illustrated chain tension sensor is very accurate for the system requirements and simple to manufacture. Although the chain tension sensor has been described in the context of a rowing machine, it will be clear to those skilled in the art that the chain tension sensor can be used with any reciprocating chain.

[0139] Figure 7 A schematic representation of the sensor connections from one or more rowing machines 43 to the DPU 40, an input device 41 for selecting the indicator to be fed back to the rower, and a feedback output device 42 is shown. Some of the possible ways of feeding back real-time information to the rower have been mentioned previously, including alphanumeric and / or graphical displays, colored lights, audible tones, or tactile devices such as vibration generators or electrical skin stimulation. Other options can be devised; the exact method used is not an essential feature of the technology.

[0140] Similarly, the indicator selection device 41 is not an essential feature of the technology, and the device can include buttons, a keyboard, a touchpad, or even voice recognition, so that the rower can change the feedback indicator while still rowing.

[0141] Another advantage of the technology is that the data required by the DPU to produce the selected indicator can be obtained from a conventional rowing machine with a minimum number of additional devices and relatively low cost. For example, Figure 2The specific implementation of the sliding base shown in the middle has been manufactured as an add-on for a commonly used rowing machine, and the additional rotation sensor and chain force sensor identified herein can be manufactured at low cost and added retrospectively to existing rowing machines and sliding bases by a reasonably unskilled person.

Claims

1. A system for providing real-time performance feedback on a rowing machine, the rowing machine comprising: a load cell coupled to a support rail; a seat coupled to the support rail for supporting a rower; a handle coupled to the load cell and arranged to be moved relative to the load cell by a pulling action on the handle; and a footrest coupled to the support rail and arranged to receive a pushing action of a foot; the system comprising: a first sensor configured to measure a first parameter indicative of the pulling action on the handle; a second sensor configured to measure a second parameter indicative of a speed of movement of an element of the rowing machine caused by the pushing action received by the footrest; a data processing unit (DPU) configured to determine a relationship between the pulling action on the handle and the pushing action received by the footrest based on the first parameter and the second parameter; wherein the footrest is rigidly coupled to the load cell and the load cell is slidably coupled to the support rail, wherein the second sensor is configured to measure a speed of movement of the load cell relative to the support rail as the second parameter; or wherein the footrest is slidably coupled to the support rail and coupled to the load cell by means of a second chain or a second cable, wherein the footrest is arranged to move along the support rail relative to the load cell, wherein the second sensor is configured to measure a speed of movement of the footrest relative to the support rail as the second parameter.

2. A system for providing real-time performance feedback on a rowing machine according to claim 1, wherein the handle is coupled to the load cell by means of a first chain or a first cable, and wherein the first sensor is coupled to the first chain or the first cable and is configured to measure a tension applied to the first chain or the first cable when pulling on the handle as the first parameter to determine a pulling force.

3. A system for providing real-time performance feedback on a rowing machine according to claim 1, wherein the load cell comprises a flywheel, wherein the first sensor is configured to measure the first parameter indicative of the pulling action on the handle by measuring an angular acceleration of the flywheel to derive a pulling force.

4. A computer-implemented method of providing real-time performance feedback on a rowing machine, the rowing machine comprising: a load cell coupled to a support rail; a seat coupled to the support rail for supporting a rower; a handle coupled to the load cell and arranged to be moved relative to the load cell by a pulling action on the handle; and a footrest coupled to the support rail and arranged to receive a pushing action of a foot, the method comprising: measuring a first parameter indicative of the pulling action on the handle; measuring a second parameter indicative of a speed of movement of an element of the rowing machine caused by the pushing action received by the footrest support; and determining in real time a relationship between the pulling action on the handle and the pushing action received by the footrest support based on the first parameter and the second parameter; wherein the footrest support is rigidly coupled to the load unit and the load unit is slidably coupled to the support rail, and measuring the second parameter comprises measuring a speed of movement Vluw of the load unit relative to the support rail; or, wherein the footrest support is slidably coupled to the support rail and coupled to the load unit by means of a second chain or a second cable, wherein the footrest support is arranged to move along the support rail relative to the load unit, wherein measuring the second parameter comprises measuring a speed of movement Vfw of the footrest support relative to the support rail.

5. A computer-implemented method of providing real-time performance feedback on a rowing machine according to claim 4, further comprising using the measured movement of the load unit to derive a pushing force Ff caused by the pushing action received by the footrest support, the method further comprising determining a power Pfw of the pushing action delivered to the footrest support using the pushing force Ff received by the footrest support and the speed of movement Vluw of the load unit according to the following equation; Pfw = -Ff * Vluw.

6. A computer-implemented method of providing real-time performance feedback on a rowing machine according to claim 4, further comprising measuring a power Pfw of the pushing action delivered to the footrest support using a pushing force Tf received by the footrest support and the speed Vfw of the footrest support according to the following equation; Pfw = -Tf * Vfw.

7. A computer-implemented method of providing real-time performance feedback on a rowing machine according to claim 4, determining a ratio of parameters between the pulling action on the handle and the pushing action received by the footrest support based on the first parameter and the second parameter.

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