Power output and metabolic cost of synchronous and asynchronous submaximal and peak level hand cycling on a motor driven treadmill in able-bodied male subjects

Steering Does Affect Biophysical Responses in Asynchronous, but Not Synchronous Submaximal Handcycle Ergometry in Able-Bodied Men

Real-life daily handcycling requires combined propulsion and steering to control the front wheel. Today, the handcycle cranks are mostly mounted synchronously unlike the early handcycle generations. Alternatively, arm cycle ergometers do not require steering and the cranks are mostly positioned asynchronously. The current study aims to evaluate the effects of combining propulsion and steering requirements on synchronous and asynchronous submaximal handcycle ergometry. We hypothesize that asynchronous handcycling with steering results in the mechanically least efficient condition, due to compensation for unwanted rotations that are not seen in synchronous handcycling, regardless of steering. Sixteen able-bodied male novices volunteered in this lab-based experiment. The set-up consisted of a handcycle ergometer with 3D force sensors at each crank that also allows “natural” steering. Four submaximal steady-state (60 rpm, ~35 W) exercise conditions were presented in a counterbalanced order: synchronous with a fixed steering axis, synchronous with steering, asynchronous with a fixed axis and asynchronous with steering. All participants practiced 3 × 4 mins with 30 mins rest in between every condition. Finally, they did handcycle for 4 mins in each of the four conditions, interspaced with 10 mins rest, while metabolic outcomes, kinetics and kinematics of the ergometer were recorded. The additional steering component did not influence velocity, torque and power production during synchronous handcycling and therefore resulted in an equal metabolically efficient handcycling configuration compared to the fixed condition. Contrarily, asynchronous handcycling with steering requirements showed a reduced mechanical efficiency, as velocity around the steering axis increased and torque and power production were less effective. Based on the torque production around the crank and steering axes, neuromuscular compensation strategies seem necessary to prevent steering movements in the asynchronous mode. To practice or test real-life daily synchronous handcycling, a synchronous crank set-up of the ergometer is advised, as exercise performance in terms of mechanical efficiency, metabolic strain, and torque production is independent of steering requirements in that mode. Asynchronous handcycling or arm ergometry demands a different handcycle technique in terms of torque production and results in higher metabolic responses than synchronous handcycling, making it unsuitable for testing.

Musculoskeletal Model Personalization Affects Metabolic Cost Estimates for Walking

Assessment of metabolic cost as a metric for human performance has expanded across various fields within the scientific, clinical, and engineering communities. As an alternative to measuring metabolic cost experimentally, musculoskeletal models incorporating metabolic cost models have been developed. However, to utilize these models for practical applications, the accuracy of their metabolic cost predictions requires improvement. Previous studies have reported the benefits of using personalized musculoskeletal models for various applications, yet no study has evaluated how model personalization affects metabolic cost estimation. This study investigated the effect of musculoskeletal model personalization on estimates of metabolic cost of transport (CoT) during post-stroke walking using three commonly used metabolic cost models. We analyzed walking data previously collected from two male stroke survivors with right-sided hemiparesis. The three metabolic cost models were implemented within three musculoskeletal modeling approaches involving different levels of personalization. The first approach used a scaled generic OpenSim model and found muscle activations via static optimization (SOGen). The second approach used a personalized electromyographic (EMG)-driven musculoskeletal model with personalized functional axes but found muscle activations via static optimization (SOCal). The third approach used the same personalized EMG-driven model but calculated muscle activations directly from EMG data (EMGCal). For each approach, the muscle activation estimates were used to calculate each subject’s CoT at different gait speeds using three metabolic cost models (Umberger et al., 2003; Bhargava et al., 2004; Umberger, 2010). The calculated CoT values were compared with published CoT data as a function of walking speed, step length asymmetry, stance time asymmetry, double support time asymmetry, and severity of motor impairment (i.e., Fugl-Meyer score). Overall, only SOCal and EMGCal with the Bhargava metabolic cost model were able to reproduce accurately published experimental trends between CoT and various clinical measures of walking asymmetry post-stroke. Tuning of the parameters in the different metabolic cost models could potentially resolve the observed CoT magnitude differences between model predictions and experimental measurements. Realistic CoT predictions may allow researchers to predict human performance, surgical outcomes, and rehabilitation outcomes reliably using computational simulations.

Biomechanical and physiological differences between synchronous and asynchronous low intensity handcycling during practice-based learning in able-bodied men

BACKGROUND

Originally, the cranks of a handcycle were mounted with a 180° phase shift (asynchronous). However, as handcycling became more popular, the crank mode switched to a parallel mounting (synchronous) over the years. Differences between both modes have been investigated, however, not into great detail for propulsion technique or practice effects. Our aim is to compare both crank modes from a biomechanical and physiological perspective, hence considering force and power production as a cause of physiological outcome measures. This is done within a practice protocol, as it is expected that motor learning takes place in the early stages of handcycling in novices.

METHODS

Twelve able-bodied male novices volunteered to take part. The experiment consisted of a pre-test, three practice sessions and a post-test, which was subsequently repeated for both crank modes in a counterbalanced manner. In each session the participants handcycled for 3 × 4 minutes on a leveled motorized treadmill at 1.94 m/s. Inbetween sessions were 2 days of rest. 3D forces, handlebar and crank angle were measured on the left hand side. Kinematic markers were placed on the handcycle to monitor the movement on the treadmill. Lastly, breath-by-breath spirometry combined with heart-rate were continuously measured. The effects of crank mode and practice-based learning were analyzed using a two way repeated measures ANOVA, with synchronous vs asynchronous and pre-test vs post-test as within-subject factors.

RESULTS

In the pre-test, asynchronous handcycling was less efficient than synchronous handcycling in terms of physiological strain, force production and timing. At the post-test, the metabolic costs were comparable for both modes. The force production was, also after practice, more efficient in the synchronous mode. External power production, crank rotation velocity and the distance travelled back and forwards on the treadmill suggest that asynchronous handcycling is more constant throughout the cycle.

CONCLUSIONS

As the metabolic costs were reduced in the asynchronous mode, we would advise to include a practice period, when comparing both modes in scientific experiments. For handcycle users, we would currently advise a synchronous set-up for daily use, as the force production is more effective in the synchronous mode, even after practice.

Shoulder and thorax kinematics contribute to increased power output of competitive handcyclists

Current knowledge of recumbent handbike configuration and handcycling technique is limited. The purpose of this study was to evaluate and compare the upper limb kinematics and handbike configurations of recreational and competitive recumbent handcyclists, during sport‐specific intensities. Thirteen handcyclists were divided into two significantly different groups based on peak aerobic power output (PO_peak) and race experience; competitive (n = 7; 5 H3 and 2 H4 classes; PO_peak: 247 ± 20 W) and recreational (n = 6; 4 H3 and 2 H4 classes; PO_peak: 198 ± 21 W). Participants performed bouts of exercise at training (50% PO_peak), competition (70% PO_peak), and sprint intensity while three‐dimensional kinematic data (thorax, scapula, shoulder, elbow, and wrist) were collected. Statistical parametric mapping was used to compare the kinematics of competitive and recreational handcyclists. Handbike configurations were determined from additional markers on the handbike. Competitive handcyclists flexed their thorax (~5°, P < 0.05), extended their shoulder (~10°, P < 0.01), and posteriorly tilted their scapular (~15°, P < 0.05) more than recreational handcyclists. Differences in scapular motion occurred only at training intensity while differences in shoulder extension and thorax flexion occurred both at training and competition intensities. No differences were observed during sprinting. No significant differences in handbike configuration were identified. This study is the first to compare the upper limb kinematics of competitive recreational handcyclists at sport‐specific intensities. Competitive handcyclists employed significantly different propulsion strategies at training and competition intensities. Since no differences in handbike configuration were identified, these kinematic differences could be due to technical training adaptations potentially optimizing muscle recruitment or force generation of the arm.

Elite handcycling: a qualitative analysis of recumbent handbike configuration for optimal sports performance

Our understanding of handbike configuration is limited, yet it can be a key determinant of performance in handcycling. This study explored how 14 handcycling experts (elite handcyclists, coaches, support staff, and manufacturers) perceived aspects of recumbent handbike configuration to impact upon endurance performance via semi-structured interviews. Optimising the handbike for comfort, stability, and power production was identified as key themes. Comfort and stability were identified to be the foundations of endurance performance and were primarily influenced by the seat, backrest, headrest, and their associated padding. Power production was determined by the relationship between the athletes' shoulder and abdomen and the trajectories of the handgrips, which were determined by the crank axis position, crank arm length, and handgrip width. Future studies should focus on quantifying the configuration of recumbent handbikes before determining the effects that crank arm length, handgrip width, and crank position have on endurance performance. Practitioner Summary: To gain a greater understanding of the impact of handbike configurations on endurance performance, the perceptions of expert handcyclists were explored qualitatively. Optimising the handbike for comfort and stability, primarily via backrest padding and power production, the position of the shoulders relative to handgrips and crank axis, were critical.

Changing relative crank angle increases the metabolic cost of leg cycling

PURPOSE

Historically, the efficiency of leg cycling has been difficult to change. However, arm cycling research indicates that relative crank angle changes can improve efficiency. Therefore, we investigated if leg cycling with different relative crank angles affects efficiency.

METHODS

Ten healthy, male, recreational bicycle riders (27.8 ± 8.2 years, mean ± SD, mass 69.8 ± 3.2 kg) pedaled a pan-loaded cycle ergometer at a fixed power output of 150 watts at a cadence of 90 RPM. Each subject completed six, 5-min trials in random order at relative crank angles of 180°, 135°, 90°, 45°, 0°, and 180°. We averaged rates of oxygen uptake ([Formula: see text]) and carbon dioxide production ([Formula: see text]), and respiratory exchange ratio (RER) for the last 2 min of each trial.

RESULTS

Crank angles other than 180° required a greater metabolic cost. As relative crank angle decreased from 180°, metabolic power monotonically increased by 1.6% at 135° to 8.2% greater when the relative crank angle was 0° (p < 0.001).

CONCLUSIONS

We find that, unlike arm cycling, radically changing the relative crank angle on a bicycle from an out-of-phase (180°) to in-phase (0°) position decreases leg cycling efficiency by ~8%. We attribute the increase to changes in cost of breathing, muscle co-activation, trunk stabilization, power fluctuations, and possibly lifting the legs during the upstroke. Our findings may have relevance in the rehabilitation of patients recovering from stroke or spinal cord injury.

APAs Constraints to Voluntary Movements: The Case for Limb Movements Coupling

When rhythmically moving two limbs in either the same or in opposite directions, one coupling mode meets constraints that are absent in the other mode. Isodirectional (ISO) flexion-extensions of the ipsilateral hand and foot can be easily performed with either the hand prone or supine. Instead, antidirectional (ANTI) movements require attentive effort and irresistibly tend to reverse into ISO when frequency increases. Experimental evidence indicates that the direction dependent easy-difficult dichotomy is caused by interference of the anticipatory postural commands associated to movements of one limb with voluntary commands to the other limb. Excitability of the resting wrist muscles is subliminally modulated at the period of ipsilateral foot oscillations, being phase-opposite in the antagonists and distributed so as to facilitate ISO and obstacle ANTI coupling of the hand (either prone or supine) with the foot. Modulation is driven by cortical signals dispatched to the forearm simultaneously with the voluntary commands moving the foot. If right foot oscillations are performed when standing on the left foot with the right hand touching a fixed support, the subliminal excitability modulation is replaced by overt contractions of forearm muscles conforming the APAs features. This suggests that during hand-foot ANTI coupling the voluntary commands to forearm muscles are contrasted by APAs commands of opposite sign linked to foot oscillations. Correlation between the easy-difficult dichotomy and the APAs distribution is also found in coupled adduction-abduction of the arms or hands in the transverse plane and in coupled flexion-extension of the arms in the parasagittal plane. In all these movements, APAs commands linked to the movement of each limb reach the motor pathways to the contralateral muscles homologous to the prime movers and can interfere during coupling with their voluntary activation. APAs are also generated in postural muscles of trunk and lower limbs and size-increase when the movement frequency is incremented. The related increase in postural effort apparently contributes in destabilizing the difficult coupling mode. Motor learning may rely upon more effective APAs. APAs and focal contraction are entangled within the same voluntary action. Yet, neural diseases may selectively impair APAs, which represent a potential target for rehabilitation.

Influence of noncircular chainring on male physiological parameters in hand cycling

The purpose of this study was to examine the influence of a noncircular chainring (NCC) compared with a conventional circular chainring (CC) on hand cycling performance. Eleven nondisabled male participants with no hand cycling experience initially completed an incremental exercise test. Afterward, the participants completed two 20 s sprint tests, followed by a 20 min endurance test and then another two 20 s sprint tests. An NCC and a CC were used in random order on two separate occasions. To compare the effects of the NCC and CC on power data of the sprint tests and metabolic response during the endurance test, a two-way analysis of variance for repeated measures was used. Average power values of the sprint tests showed no significant difference between NCC and CC, but over time, values of the first and third sprint tests were higher than those of the second and fourth sprint tests for both chainrings. Values of energy expenditure (kilojoules), gross efficiency (percentage), and net efficiency (percentage) after 10 and 20 min during the endurance test using NCC and CC showed no significant differences (p > 0.05) either between tests or over time. Under the current test conditions and focusing on physiological parameters, a performance optimization using an NCC in hand cycling could not be proven.

Effect of Three Different Grip Angles on Physiological Parameters During Laboratory Handcycling Test in Able-Bodied Participants

INTRODUCTION

Handcycling is a relatively new wheelchair sport that has gained increased popularity for people with lower limb disabilities. The aim of this study was to examine the effect of three different grip positions on physical parameters during handcycling in a laboratory setting.

METHODS

Twenty one able-bodied participants performed three maximum incremental handcycling tests until exhaustion, each with a different grip angle. The angle between the grip and the crank was randomly set at 90° (horizontal), 0° (vertical), or 10° (diagonal). The initial load was 20 W and increased by 20 W each 5 min. In addition, participants performed a 20 s maximum effort.

RESULTS

The relative peak functional performance (W/kg), peak heart rate (bpm), associated lactate concentrations (mmol/l) and peak oxygen uptake per kilogram body weight (ml.min(-1).kg(-1)) for the different grip positions during the stage test were: (a) Horizontal: 1.43 ± 0.21 W/kg, 170.14 ± 12.81 bpm, 9.54 ± 1.93 mmol/l, 30.86 ± 4.57 ml/kg; (b) Vertical: 1.38 ± 0.20 W/kg, 171.81 ± 13.87 bpm, 9.91 ± 2.29 mmol/l, 29.75 ± 5.13 ml/kg; (c) Diagonal: 1.40 ± 0.22 W/kg, 169.19 ± 13.31 bpm, 9.34 ± 2.36 mmol/l, 29.39 ± 4.70 ml/kg. Statistically significant (p < 0.05) differences could only be found for lactate concentration between the vertical grip position and the other grips during submaximal handcycling.

CONCLUSION

The orientation of three different grip angles made no difference to the peak load achieved during an incremental handcycling test and a 20 s maximum effort. At submaximal load, higher lactate concentrations were found when the vertical grip position was used, suggesting that this position may be less efficient than the alternative diagonal or horizontal grip positions.

Coordinating arms and legs on a hybrid rehabilitation tricycle: the metabolic benefit of asymmetrical compared to symmetrical arm movements

PURPOSE

The most commonly used propulsion method for handcycling is moving the arms symmetrically. Previous studies indicated that during outdoor handcycling symmetrical arm movements are more efficient. During locomotor movements, however, arm movements are performed asymmetrically in combination with leg movements. We questioned which combination of arm and leg movements is more efficient during combined arm and leg cycling for stationary use.

METHODS

Twenty-five able-bodied adults performed eight submaximal tests of 6 min on a hybrid handcycle at three incremental gears during four different conditions ('arms only' and 'arms & legs' with arms symmetrical and asymmetrical). Oxygen uptake (VO2), heart rate (HR) and Borg score (Borg) were assessed.

RESULTS

Increasing workload resulted in significant increases in VO2 (16 W: 13.0 ± 2.4 ml kg(-1) min(-1), 31 W: 14.5 ± 2.9, 49 W: 15.5 ± 2.8; p < 0.001) and Borg (16 W: 7.7 ± 1.7 points, 31 W: 8.6 ± 1.9, 49 W: 9.5 ± 1.9; p < 0.001). During 'arms only', no differences were found in exercise intensity between symmetrical and asymmetrical movements. Contrarily, during 'arms & legs', both VO2 (p < 0.001) and Borg (p = 0.001) were significantly lower for the asymmetrical (VO2: 13.8 ± 2.6 ml kg(-1) min(-1), Borg: 8.1 ± 1.6 points) compared to the symmetrical condition (VO2: 14.9 ± 2.8, Borg: 9.1 ± 2.0).

CONCLUSIONS

Results indicated that asymmetrical arm movements, especially in combination with leg movements, represented the most efficient condition on a stationary hybrid handcycle. The current results suggest that neural energy costs are lower when moving in the preferred (asymmetrical) coordination when no steering is required. These findings may have implications for stationary arm & leg cycling rehabilitation and tricycle adaptations in patients with spinal cord injury.

The role of anticipatory postural adjustments in interlimb coordination of coupled arm movements in the parasagittal plane: III. difference in the energy cost of postural actions during cyclic flexion-extension arm movements, ISO- and ANTI-directionally coupled

When oscillating the upper limbs together in the parasagittal plane, movements coordination is lower (i.e., variability of the interlimb relative phase is higher) in antidirectional (ANTI) than in isodirectional (ISO) coupling. In contrast, we previously observed that for arm movements in the horizontal plane, the coordination was worse in ISO than ANTI and the energetic cost of postural activities was higher in ISO. Having hypothesised that the higher postural cost was one factor responsible for the coordination deficit in horizontal ISO, we measured the oxygen uptake ([Formula: see text]) in parasagittal movements, expecting that in this case too, the postural cost is higher in the less-coordinated mode (ANTI). Breath-by-breath metabolic ([Formula: see text], [Formula: see text]) and cardiorespiratory (HR, [Formula: see text]) parameters were measured in seven participants, who performed cyclic flexions-extensions in the parasagittal plane with either one arm or both arms, in ISO or ANTI coupling and at 1.4, 2.2 and 2.6 Hz. In each condition, the intermittent exercise (12 s movement, 12 s rest) lasted 264 s. A force platform recorded the mechanical actions to the ground. The exercise metabolic cost ([Formula: see text]) was found to be significantly higher in parasagittal ANTI than ISO. The movement amplitude being equal in the two modes, the ANTI-ISO difference should be ascribed to postural activities. This would confirm that the less-coordinated coupling mode requires the higher postural effort in parasagittal movements too. When rising the movement frequency, [Formula: see text] increased and linearly correlated with the coordination loss. Comparison of parasagittal with horizontal movements showed that [Formula: see text] was lower in parasagittal ANTI than in horizontal ISO (the less-coordinated modes), while it was not different between parasagittal ISO and horizontal ANTI (the more-coordinated modes).

The role of anticipatory postural adjustments in interlimb coordination of coupled arm movements in the parasagittal plane: II. Postural activities and coupling coordination during cyclic flexion-extension arm movements, ISO- and ANTI-directionally coupled

When coupling cyclic adduction-abduction movements of the arms in the transverse (horizontal) plane, isodirectional (ISO) coupling is less stable than antidirectional (ANTI) coupling. We proposed that such deficiency stems from the disturbing action that anticipatory postural adjustments exert on ISO coupling. To ascertain if postural adjustments differentiate ISO versus ANTI coupling coordination in other types of cyclic arm movements, we examined flexion-extension oscillations in the parasagittal plane. Oscillations of the right arm alone elicited cyclic Postural Adjustments (PAs) in the left Anterior Deltoid and Posterior Deltoid, which replicated the excitation-inhibition pattern of the prime movers right Anterior Deltoid, right Posterior Deltoid. Cyclic PAs also developed symmetrically in Erector Spinae (RES and LES) and in phase opposition in Ischiocruralis (RIC and LIC), so as to discharge to the ground both an anteroposterior force, Fy, and a moment about the vertical axis, Tz. Oscillations of both arms in ISO coupling induced symmetric PAs in both ES and IC muscles, thus generating a large Fy but no Tz. In ANTI coupling, PAs in RES and LES remained symmetric but smaller in size, while PAs in RIC and LIC were large and opposite in phase, resulting in a large Tz and small Fy. Altogether, PAs would thus favour ISO and hamper ANTI parasagittal movements because (1) in the motor pathways to the prime movers of either arm, a convergence would occur between the voluntary commands and the commands for PAs linked to the movement of the other arm, the two commands having the same sign (excitatory or inhibitory) during ISO and an opposite sign during ANTI; (2) the postural effort of trunk and leg muscles would be higher for generating Tz in ANTI than Fy in ISO. These predictions fit with the finding that coupling stability was lower in ANTI than in ISO, i.e., opposite to horizontal movements. In conclusion, in both parasagittal and horizontal arm movements, the less coordinated coupling mode was the one constrained by postural adjustments through the two above mechanisms.

A Comparison of Asynchronous and Synchronous Arm Cranking During the Wingate Test

Purpose:

The aim of this study was to compare asynchronous (AS Y) arm cranking (cranks at 180° relative to each other) with synchronous (SYN) arm cranking (parallel crank setting) during the 30 s Wingate anaerobic test.

Methods:

Thirty-two physically active men (aged 22.1 ± 2.4 y) completed two Wingate tests (one ASY and one SYN) separated by 4 d in a randomized counterbalanced order. The Wingate tests were completed on a modified electromagnetically braked cycle ergometer. Performance measures assessed during the two tests include peak power, mean power, minimum power, time to peak power, rate to fatigue and maximum cadence (RPMmax). Blood lactate concentration was also measured before and 5 min after the tests.

Results:

Peak and mean power (both absolute and relative to body weight) during SYN arm cranking were significantly (p < 0.001) less than during ASY arm cranking. Rate to fatigue and RPMmax were also significantly (p = 0.012) lower during SYN arm cranking compared with ASY arm cranking. No significant difference was found between test conditions for minimum power, time to peak power or blood lactate concentration.

Conclusions:

These findings demonstrate that ASY arm cranking results in higher peak and mean anaerobic power compared with SYN arm cranking during the Wingate test. Therefore, an ASY arm crank configuration should be used to assess anaerobic power in most individuals although specific population groups may require further testing to determine which crank configuration is most suitable for the Wingate test.

Physical capacity after 7 weeks of low-intensity wheelchair training

PURPOSE

To simulate the effect of low-intensity exercise in early rehabilitation, we investigated the effect of a 7-week low-intensity norm duration hand rim wheelchair training on the physical capacity in untrained able-bodied individuals.

METHOD

Twenty-five able-bodied participants were randomly assigned to an experimental and control group: 10 participants exercised 7 weeks, three times a week at 30% heart rate reserve (HRR) for 30 min (experimental group). The control group consisted of 15 participants who did not receive training. Physical capacity (maximal isometric strength, sprint power, peak power output and peak oxygen uptake) and submaximal performance [heart rate (HR), oxygen uptake (VO₂), mechanical efficiency (ME)] were assessed pre- and post-training. The levels of upper-body discomfort were determined with the use of a Local Perceived Discomfort scale.

RESULTS

Compared to the control group the experimental group significantly improved on sprint power (+31.2%), peak aerobic power output (+34%), submaximal HR, VO₂ and ME (+16.9%). The participants did not experience high levels of local discomfort in the upper body during the training.

CONCLUSIONS

Low-intensity norm duration hand rim wheelchair training which significantly improved peak aerobic and sprint power output, efficiency and physical strain in able-bodied untrained individuals. Training at 30% HRR (3 × /week, 30 min/session) may be appropriate in untrained individuals, such as novice wheelchair users at the start of their rehabilitation, to prevent early fatigue and overuse and enhance motivation.

Submaximal arm crank ergometry: Effects of crank axis positioning on mechanical efficiency, physiological strain and perceived discomfort

PURPOSE

To evaluate the effect of the spatial orientation of the crank axis on mechanical efficiency, physiological strain and perceived discomfort in submaximal synchronous arm crank ergometry.

METHODS

Twelve able-bodied individuals performed 12 submaximal exercise bouts of 3 minutes (women: 20 W/25 W; men: 25 W/35 W). The crank axis position was defined by elbow and shoulder angle.

RESULTS

The results showed that a crank set-up with an elbow angle of 30 degrees was more efficient than 15 degrees ; oxygen consumption and minute ventilation were significantly lower. No significant effects were seen for shoulder angle. Power output and gender showed obvious effects.

DISCUSSION AND CONCLUSION

The magnitude of this effect and the absence of any significant shoulder angle effects may be due to the relative low exertion levels that were evaluated. An elbow angle of 30 degrees flexion in arm crank exercise is favourable compared to an elbow angle of 15 degrees in able-bodied untrained subjects.