Cadence Paradox in Cycling-Part 2: Theory and Simulation of Maximal Lactate Steady State and Carbohydrate Utilization Dependent on Cycling Cadence.

PURPOSE: To develop and evaluate a theory on the frequent observation that cyclists prefer cadences (RPMs) higher than those considered most economical at submaximal exercise intensities via modeling and simulation of its mathematical description. METHODS: The theory combines the parabolic power-to-velocity (v) relationship, where v is defined by crank length, RPM-dependent ankle velocity, and gear ratio, RPM effects on the maximal lactate steady state (MLSS), and lactate-dependent carbohydrate oxidation (CHO). It was tested against recent experimental results of 12 healthy male recreational cyclists determining the v-dependent peak oxygen uptake (VO2PEAKv), MLSS (MLSSv), corresponding power output (PMLSSv), oxygen uptake at PMLSSv (VO2MLSSv), and CHOMLSSv-management at 100 versus 50 per minute, respectively. Maximum RPM (RPMMAX) attained at minimized pedal torque was measured. RPM-specific maximum sprint power output (PMAXv) was estimated at RPMs of 100 and 50, respectively. RESULTS: Modeling identified that MLSSv and PMLSSv related to PMAXv (IPMLSSv) promote CHO and that VO2MLSSv related to VO2PEAKv inhibits CHO. It shows that cycling at higher RPM reduces IPMLSSv. It suggests that high cycling RPMs minimize differences in the reliance on CHO at MLSSv between athletes with high versus low RPMMAX. CONCLUSIONS: The present theory-guided modeling approach is exclusively based on data routinely measured in high-performance testing. It implies a higher performance reserve above IPMLSSv at higher RPM. Cyclists may prefer high cycling RPMs because they appear to minimize differences in the reliance on CHO at MLSSv between athletes with high versus low RPMMAX.

Understanding optimal cadence dynamics: a systematic analysis of the power-velocity relationship in track cyclists with increasing exercise intensity.

Background: This study aimed to investigate the changes in force-velocity (F/v) and power-velocity (P/v) relationships with increasing work rate up to maximal oxygen uptake and to assess the resulting alterations in optimal cadence, particularly at characteristic metabolic states. Methods: Fourteen professional track cyclists (9 sprinters, 5 endurance athletes) performed submaximal incremental tests, high-intensity cycling trials, and maximal sprints at varied cadences (60, 90, 120 rpm) on an SRM bicycle ergometer. Linear and non-linear regression analyses were used to assess the relationship between heart rate, oxygen uptake (V.O2), blood lactate concentration and power output at each pedaling rate. Work rates linked to various cardiopulmonary and metabolic states, including lactate threshold (LT1), maximal fat combustion (FATmax), maximal lactate steady-state (MLSS) and maximal oxygen uptake (V.O2max), were determined using cadence-specific inverse functions. These data were used to calculate state-specific force-velocity (F/v) and power-velocity (P/v) profiles, from which state-specific optimal cadences were derived. Additionally, fatigue-free profiles were generated from sprint data to illustrate the entire F/v and P/v continuum. Results: HR, V.O2 demonstrated linear relationships, while BLC exhibited an exponential relationship with work rate, influenced by cadence (p < 0.05, η2 ≥ 0.655). Optimal cadence increased sigmoidally across all parameters, ranging from 66.18 ± 3.00 rpm at LT1, 76.01 ± 3.36 rpm at FATmax, 82.24 ± 2.59 rpm at MLSS, culminating at 84.49 ± 2.66 rpm at V.O2max (p < 0.01, η2 = 0.936). A fatigue-free optimal cadence of 135 ± 11 rpm was identified. Sprinters and endurance athletes showed no differences in optimal cadences, except for the fatigue-free optimum (p < 0.001, d = 2.215). Conclusion: Optimal cadence increases sigmoidally with exercise intensity up to maximal aerobic power, irrespective of the athlete's physical condition or discipline. Threshold-specific changes in optimal cadence suggest a shift in muscle fiber type recruitment toward faster types beyond these thresholds. Moreover, the results indicate the need to integrate movement velocity into Henneman's hierarchical size principle and the critical power curve. Consequently, intensity zones should be presented as a function of movement velocity rather than in absolute terms.

Cadence Paradox in Cycling-Part 1: Maximal Lactate Steady State and Carbohydrate Utilization Dependent on Cycling Cadence.

PURPOSE: To assess (1) whether and how a higher maximal lactate steady state (MLSS) at higher cycling cadence (RPM) comes along with higher absolute and/or fractional carbohydrate combustion (CHOMLSS), respectively, and (2) whether there is an interrelation between potential RPM-dependent MLSS effects and the maximally achievable RPM (RPMMAX). METHODS: Twelve healthy males performed incremental load tests to determine peak power, peak oxygen uptake, and 30-minute MLSS tests at 50 and 100 per minute, respectively, to assess RPM-dependent MLSS, corresponding power output, CHOMLSS responses, and 6-second sprints to measure RPMMAX. RESULTS: Peak power, peak carbon dioxide production, and power output at MLSS were lower (P = .000, ω2 = 0.922; P = .044, ω2 > 0.275; and P = .016, ω2 = 0.373) at 100 per minute than at 50 per minute. With 6.0 (1.5) versus 3.8 (1.2) mmol·L-1, MLSS was higher (P = .000, ω2 = 0.771) at 100 per minute than at 50 per minute. No corresponding RPM-dependent differences were found in oxygen uptake at MLSS, carbon dioxide production at MLSS, respiratory exchange ratio at MLSS, CHOMLSS, or fraction of oxygen uptake used for CHO at MLSS, respectively. There was no correlation between the RPM-dependent difference in MLSS and RPMMAX. CONCLUSIONS: The present study extends the previous finding of a consistently higher MLSS at higher RPM by indicating (1) that at fully established MLSS conditions, respiration and CHOMLSS management do not differ significantly between 100 per minute and 50 per minute, and (2) that linear correlation models did not identify linear interdependencies between RPM-dependent MLSS conditions and RPMMAX.

Evaluation of temporal, spatial and spectral filtering in CSP-based methods for decoding pedaling-based motor tasks using EEG signals.

Stroke is a neurological syndrome that usually causes a loss of voluntary control of lower/upper body movements, making it difficult for affected individuals to perform Activities of Daily Living (ADLs). Brain-Computer Interfaces (BCIs) combined with robotic systems, such as Motorized Mini Exercise Bikes (MMEB), have enabled the rehabilitation of people with disabilities by decoding their actions and executing a motor task. However, Electroencephalography (EEG)-based BCIs are affected by the presence of physiological and non-physiological artifacts. Thus, movement discrimination using EEG become challenging, even in pedaling tasks, which have not been well explored in the literature. In this study, Common Spatial Patterns (CSP)-based methods were proposed to classify pedaling motor tasks. To address this, Filter Bank Common Spatial Patterns (FBCSP) and Filter Bank Common Spatial-Spectral Patterns (FBCSSP) were implemented with different spatial filtering configurations by varying the time segment with different filter bank combinations for the three methods to decode pedaling tasks. An in-house EEG dataset during pedaling tasks was registered for 8 participants. As results, the best configuration corresponds to a filter bank with two filters (8-19 Hz and 19-30 Hz) using a time window between 1.5 and 2.5 s after the cue and implementing two spatial filters, which provide accuracy of approximately 0.81, False Positive Rates lower than 0.19, andKappaindex of 0.61. This work implies that EEG oscillatory patterns during pedaling can be accurately classified using machine learning. Therefore, our method can be applied in the rehabilitation context, such as MMEB-based BCIs, in the future.

Concurrent Validity and Reliability of Two Portable Powermeters (Power2Max vs. PowerTap) to Measure Different Types of Efforts in Cycling.

The purpose was to assess the concurrent validity and reliability of two portable powermeters (PowerTap vs. Power2Max) in different types of cycling efforts. Ten cyclists performed two submaximal, one incremental maximal and two supramaximal sprint tests on an ergometer, while pedaling power and cadence were registered by both powermeters and a cadence sensor (GarminGSC10). During the submaximal and incremental maximal tests, significant correlations were found for power and cadence data (r = 0.992-0.997 and 0.996-0.998, respectively, p < 0.001), with a slight power underestimation by PowerTap (0.7-1.8%, p < 0.01) and a high reliability of both powermeters (p < 0.001) for measurement of power (ICC = 0.926 and 0.936, respectively) and cadence (ICC = 0.969 and 0.970, respectively). However, during the supramaximal sprint test, their agreement to measure power and cadence was weak (r = 0.850 and -0.253, p < 0.05) due to the low reliability of the cadence measurements (ICC between 0.496 and 0.736, and 0.574 and 0.664, respectively; p < 0.05) in contrast to the high reliability of the cadence sensor (ICC = 0.987-0.994). In conclusion, both powermeters are valid and reliable for measuring power and cadence during continuous cycling efforts (~100-450 W), but questionable during sprint efforts (>500 W), where they are affected by the gear ratio used (PowerTap) and by their low accuracy in cadence recording (PowerTap and Power2Max).

Power production strategy during steady-state cycling is cadence dependent.

Crank power is produced by extension and flexion of the hip and knee joints during steady-state pedaling below 120 rpm. Despite the pedaling cadence exceeding 120 rpm during track cycling, the power production strategy for lower-limb coordination above 120 rpm is unknown. This study aimed to assess the effects of various pedaling cadences on the power production strategy of lower-limb coordination during steady-state pedaling. Twenty trained collegiate cyclists performed a 30-s steady-state pedaling exercise at 50% of maximal anaerobic power under four different conditions with 90-, 120-, 150- and 180-rpm pedaling cadences. Pedal kinetics and limb kinematics were recorded using a pedal force measurement system and motion capture system, respectively. Positive mechanical work of hip extension significantly decreased with increasing pedaling cadence (P < 0.05). In contrast, the positive mechanical work of the knee joint flexion significantly increased with increasing pedaling cadence (P < 0.05). For contribution to the total mechanical work at 150 or above rpm, the knee joint showed > 70% of the total contribution, whereas the hip joint showed < 40%. Additionally, the positive mechanical work of the hip shifted to negative mechanical work under 180-rpm condition. These results indicate that power production strategy during steady-state pedaling at 180 rpm is different from the general pedaling cadence. Therefore, specific training needs to be conducted at an excessive-high pedaling cadence such as 180 rpm to achieve high performance in track cycling.

Torque Measurement and Control for Electric-Assisted Bike Considering Different External Load Conditions.

This paper proposes a novel torque measurement and control technique for cycling-assisted electric bikes (E-bikes) considering various external load conditions. For assisted E-bikes, the electromagnetic torque from the permanent magnet (PM) motor can be controlled to reduce the pedaling torque generated by the human rider. However, the overall cycling torque is affected by external loads, including the cyclist's weight, wind resistance, rolling resistance, and the road slope. With knowledge of these external loads, the motor torque can be adaptively controlled for these riding conditions. In this paper, key E-bike riding parameters are analyzed to find a suitable assisted motor torque. Four different motor torque control methods are proposed to improve the E-bike's dynamic response with minimal variation in acceleration. It is concluded that the wheel acceleration is important to determine the E-bike's synergetic torque performance. A comprehensive E-bike simulation environment is developed with MATLAB/Simulink to evaluate these adaptive torque control methods. In this paper, an integrated E-bike sensor hardware system is built to verify the proposed adaptive torque control.

Inflammatory Process on Knee Osteoarthritis in Cyclists.

Osteoarthritis is a disorder affecting the joints and is characterized by cellular stress and degradation of the extracellular matrix cartilage. It begins with the presence of micro- and macro-lesions that fail to repair properly, which can be initiated by multiple factors: genetic, developmental, metabolic, and traumatic. In the case of the knee, osteoarthritis affects the tissues of the diarthrodial joint, manifested by morphological, biochemical, and biomechanical modifications of the cells and the extracellular matrix. All this leads to remodeling, fissuring, ulceration, and loss of articular cartilage, as well as sclerosis of the subchondral bone with the production of osteophytes and subchondral cysts. The symptomatology appears at different time points and is accompanied by pain, deformation, disability, and varying degrees of local inflammation. Repetitive concentric movements, such as while cycling, can produce the microtrauma that leads to osteoarthritis. Aggravation of the gradual lesion in the cartilage matrix can evolve to an irreversible injury. The objective of the present review is to explain the evolution of knee osteoarthritis in cyclists, to show the scarce research performed in this particular field and extract recommendations to propose future therapeutic strategies.

Lower-limb kinematic reconstruction during pedaling tasks from EEG signals using Unscented Kalman filter.

Kinematic reconstruction of lower-limb movements using electroencephalography (EEG) has been used in several rehabilitation systems. However, the nonlinear relationship between neural activity and limb movement may challenge decoders in real-time Brain-Computer Interface (BCI) applications. This paper proposes a nonlinear neural decoder using an Unscented Kalman Filter (UKF) to infer lower-limb kinematics from EEG signals during pedaling. The results demonstrated maximum decoding accuracy using slow cortical potentials in the delta band (0.1-4 Hz) of 0.33 for Pearson's r-value and 8 for the signal-to-noise ratio (SNR). This leaves an open door to the development of closed-loop EEG-based BCI systems for kinematic monitoring during pedaling rehabilitation tasks.

Effects of Very Low- and High-Frequency Subthalamic Stimulation on Motor Cortical Oscillations During Rhythmic Lower-Limb Movements in Parkinson's Disease Patients.

BACKGROUND: Standard high-frequency deep brain stimulation (HF-DBS) at the subthalamic nucleus (STN) is less effective for lower-limb motor dysfunctions in Parkinson's disease (PD) patients. However, the effects of very low frequency (VLF; 4 Hz)-DBS on lower-limb movement and motor cortical oscillations have not been compared. OBJECTIVE: To compare the effects of VLF-DBS and HF-DBS at the STN on a lower-limb pedaling motor task and motor cortical oscillations in patients with PD and with and without freezing of gait (FOG). METHODS: Thirteen PD patients with bilateral STN-DBS performed a cue-triggered lower-limb pedaling motor task with electroencephalography (EEG) in OFF-DBS, VLF-DBS (4 Hz), and HF-DBS (120-175 Hz) states. We performed spectral analysis on the preparatory signals and compared GO-cue-triggered theta and movement-related beta oscillations over motor cortical regions across DBS conditions in PD patients and subgroups (PDFOG-and PDFOG+). RESULTS: Both VLF-DBS and HF-DBS decreased the linear speed of the pedaling task in PD, and HF-DBS decreased speed in both PDFOG-and PDFOG+. Preparatory theta and beta activities were increased with both stimulation frequencies. Both DBS frequencies increased motor cortical theta activity during pedaling movement in PD patients, but this increase was only observed in the PDFOG + group. Beta activity was not significantly different from OFF-DBS at either frequency regardless of FOG status. CONCLUSION: Results suggest that VL and HF DBS may induce similar effects on lower-limb kinematics by impairing movement speed and modulating motor cortical oscillations in the lower frequency band.

Two weeks of arm cycling sprint interval training enhances spinal excitability to the biceps brachii.

The present study aimed to investigate whether a 2-wk arm cycling sprint interval training (SIT) program modulated corticospinal pathway excitability in healthy, neurologically intact participants. We employed a pre-post study design with two groups: 1) an experimental SIT group and 2) a nonexercising control group. Transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of corticospinal axons were used at baseline and post-training to provide indices of corticospinal and spinal excitability, respectively. Stimulus-response curves (SRCs) recorded from the biceps brachii were elicited for each stimulation type during two submaximal arm cycling conditions [25 watts (W) and 30% peak power output (PPO)]. All stimulations were delivered during the mid-elbow flexion phase of cycling. Compared with baseline, performance on the time-to-exhaustion (TTE) test at post-testing was improved for members of the SIT group but was not altered for controls, suggesting that SIT improved exercise performance. There were no changes in the area under the curve (AUC) for TMS-elicited SRCs for either group. However, the AUC for TMES-elicited cervicomedullary motor-evoked potential SRCs were significantly larger at post-testing in the SIT group only (25 W: P = 0.012, d = 0.870; 30% PPO: P = 0.016, d = 0.825). This data shows that overall corticospinal excitability is unchanged following SIT, whereas spinal excitability is enhanced. Although the precise mechanisms underlying these findings during arm cycling at post-SIT are unknown, it is suggested that the enhanced spinal excitability may represent a neural adaptation to training.NEW & NOTEWORTHY Two weeks of arm cycling sprint interval training (SIT) improves subsequent aerobic exercise performance and induces changes within the descending corticospinal pathway. Specifically, spinal excitability is enhanced following training, whereas overall corticospinal excitability does not change. These results suggest that the enhanced spinal excitability may represent a neural adaptation to training. Future work is required to discern the precise neurophysiological mechanisms underlying these observations.

Pre-stimulus beta power varies as a function of auditory-motor synchronization and temporal predictability.

Introduction: Auditory-motor interactions can support the preparation for expected sensory input. We investigated the periodic modulation of beta activity in the electroencephalogram to assess the role of active auditory-motor synchronization. Pre-stimulus beta activity (13-30 Hz) has been interpreted as a neural signature of the preparation for expected sensory input. Methods: In the current study, participants silently counted frequency deviants in sequences of pure tones either during a physically inactive control condition or while pedaling on a cycling ergometer. Tones were presented either rhythmically (at 1 Hz) or arrhythmically with variable intervals. In addition to the pedaling conditions with rhythmic (auditory-motor synchronization, AMS) or arrhythmic stimulation, a self-generated stimulus condition was used in which tones were presented in sync with the participants' spontaneous pedaling. This condition served to explore whether sensory predictions are driven primarily by the auditory or by the motor system. Results: Pre-stimulus beta power increased for rhythmic compared to arrhythmic stimulus presentation in both sitting and pedaling conditions but was strongest in the AMS condition. Furthermore, beta power in the AMS condition correlated with motor performance, i.e., the better participants synchronized with the rhythmic stimulus sequence, the higher was pre-stimulus beta power. Additionally, beta power was increased for the self-generated stimulus condition compared with arrhythmic pedaling, but there was no difference between the self-generated and the AMS condition. Discussion: The current data pattern indicates that pre-stimulus beta power is not limited to neuronal entrainment (i.e., periodic stimulus presentation) but represents a more general correlate of temporal anticipation. Its association with the precision of AMS supports the role of active behavior for auditory predictions.

Pedal cadence does not affect muscle damage to eccentric cycling performed at similar mechanical work.

Purpose: This study aimed to investigate muscle damage when performing equal mechanical work of fast and slow pedaling speed by eccentric muscle actions (ECCs) cycling. Methods: Nineteen young men [mean ± standard deviation (SD) age: 21.0 ± 2.2 years; height: 172.7 ± 5.9 cm; and body mass: 70.2 ± 10.5 kg] performed maximal effort of ECCs cycling exercise with fast speed (Fast) and slow speed trials (Slow). First, subjects performed the Fast for 5 min by one leg. Second, Slow performed until the total mechanical work was equal to that generated during Fast other one leg. Changes in maximal voluntary isometric contraction (MVC) torque of knee extension, isokinetic pedaling peak torque (IPT), range of motion (ROM), muscle soreness, thigh circumference, muscle echo intensity, and muscle stiffness were assessed before exercise, and immediately after exercise, and 1 and 4 days after exercise. Results: Exercise time was observed in the Slow (1422.0 ± 330.0 s) longer than Fast (300.0 ± 0.0 s). However, a significant difference was not observed in total work (Fast:214.8 ± 42.4 J/kg, Slow: 214.3 ± 42.2 J/kg). A significant interaction effect was not observed in peak values of MVC torque (Fast:1.7 ± 0.4 Nm/kg, Slow: 1.8 ± 0.5 Nm/kg), IPT, muscle soreness (Fast:4.3 ± 1.6 cm, Slow: 4.7 ± 2.9 cm). In addition, ROM, circumference, muscle thickness, muscle echo intensity, and muscle stiffness also showed no significant interaction. Conclusion: The magnitude of muscle damage is similar for ECCs cycling with equal work regardless of velocity.

Effects of Different Pedaling Positions on Muscle Usage and Energy Expenditure in Amateur Cyclists.

BACKGROUND: Inappropriate cycling positions may affect muscle usage strategy and raise the level of fatigue or risk of sport injury. Dynamic bike fitting is a growing trend meant to help cyclists select proper bikes and adjust them to fit their ergometry. The purpose of this study is to investigate how the "knee forward of foot" (KFOF) distance, an important dynamic bike fitting variable, influences the muscle activation, muscle usage strategy, and rate of energy expenditure during cycling. METHODS: Six amateur cyclists were recruited to perform the short-distance ride test (SRT) and the graded exercise tests (GXT) with pedaling positions at four different KFOF distances (+20, 0, -20, and -40 mm). The surface electromyographic (EMG) and portable energy metabolism systems were used to monitor the muscle activation and energy expenditure. The outcome measures included the EMG root-mean-square (RMS) amplitudes of eight muscles in the lower extremity during the SRT, the regression line of the changes in the EMG RMS amplitude and median frequency (MF), and the heart rate and oxygen consumption during the GXT. RESULTS: Our results revealed significant differences in the muscle activation of vastus lateralis, vastus medialis, and semitendinosus among four different pedaling positions during the SRT. During GXT, no statistically significant differences in muscle usage strategy and energy expenditure were found among different KFOF. However, most cyclists had the highest rate of energy expenditure with either KFOF at -40 mm or 20 mm. CONCLUSIONS: The KFOF distance altered muscle activation in the SRT; however, no significant influence on the muscle usage strategy was found in the GXT. A higher rate of energy expenditure in the extreme pedaling positions of KFOF was observed in most amateur cyclists, so professional assistance for proper bike fitting was recommended.

The relationship between pedal force application technique and the ability to perform supramaximal pedaling cadences.

This study aimed to examine the relationship between the pedal force application technique under a specific competitive condition and the ability to perform steady-state pedaling at a supramaximal cadence during a special pedaling test. A total of 15 competitive male cyclists and 13 active, healthy men (novice cyclists, hereafter, novices) performed the pedaling technique test. The test imitated a road cycling competition condition (80% VO2 peak and a cadence of 90 rpm). Additionally, they performed a supramaximal cadence test that evaluated the ability to perform steady-state pedaling for an ultra-high cadence (range of 160-220 rpm) of 30 s stably with a 0.1 kgf. For the pedaling technique test, kinetic data were obtained by the pedal-shaped force platform at 1,000 Hz, and the pedaling technique was determined by the index of force effectiveness (IFE). For the supramaximal cadence test, kinematic data were obtained using a motion capture system at 200 Hz. The supramaximal pedaling cadence (Cmax) was determined by measuring exercise time and targeted pedaling cadence. The IFE was 48.0 ± 9.7% in cyclists and 32.0 ± 5.9% in novices. The Cmax was 215.5 ± 8.8 rpm in cyclists and 192.2 ± 13.0 rpm in novices. These values were significantly higher for cyclists than for novices. Cmax was moderately correlated with IFE (r = 0.64). No significant correlation was observed between Cmax and IFE for cyclists only; in contrast, a moderate correlation was observed between these parameters for novices only (r = 0.67). In conclusion, the pedal force application technique under a specific competitive condition is related to the ability to perform steady-state pedaling for supramaximal cadence during the test. Therefore, Cmax may be able to explain pedal force application techniques without the need for expensive devices for novices.

Reliability and Variability of Lower Limb Muscle Activation as Indicators of Familiarity to Submaximal Eccentric Cycling.

Submaximal eccentric (ECC) cycling exercise is commonly used in research studies. No previous study has specified the required time naïve participants take to familiarize with submaximal ECC cycling. Therefore, we designed this study to determine whether critical indicators of cycling reliability and variability stabilize during 15 min of submaximal, semi-recumbent ECC cycling (ECC cycling). Twenty-two participants, aged between 18-51 years, volunteered to complete a single experimental session. Each participant completed three peak eccentric torque protocol (PETP) tests, nine countermovement jumps and 15 min of submaximal (i.e., 10% peak power output produced during the PETP tests) ECC cycling. Muscle activation patterns were recorded from six muscles (rectus femoris, RF; vastus lateralis, VL; vastus medialis, VM; soleus, SOL; medial gastrocnemius, GM; tibialis anterior, TA), during prescribed-intensity ECC cycling, using electromyography (EMG). Minute-to-minute changes in the reliability and variability of EMG patterns were examined using intra-class correlation coefficient (ICC) and variance ratios (VR). Differences between target and actual power output were also used as an indicator of familiarization. Activation patterns for 4/6 muscles (RF, VL, VM and GM) became more consistent over the session, the RF, VL and VM increasing from moderate (ICC = 0.5-0.75) to good (ICC = 0.75-0.9) reliability by the 11th minute of cycling and the GM good reliability from the 1st minute (ICC = 0.79, ICC range = 0.70-0.88). Low variability (VR ≤ 0.40) was maintained for VL, VM and GM from the 8th, 8th and 1st minutes, respectively. We also observed a significant decrease in the difference between actual and target power output (χ2 14 = 30.895, p = 0.006, W = 0.105), expressed primarily between the 2nd and 3rd minute of cycling (Z = -2.677, p = 0.007). Indicators of familiarization during ECC cycling, including deviations from target power output levels and the reliability and variability of muscle activation patterns stabilized within 15 min of cycling. Based upon this data, it would be reasonable for future studies to allocate ∼ 15 min to familiarize naïve participants with a submaximal ECC cycling protocol.

The Effect of Pedaling at Different Cadence on Attentional Resources.

We investigated the relationship between attentional resources and pedaling cadence using electroencephalography (EEG) to measure P300 amplitudes and latencies. Twenty-five healthy volunteers performed the oddball task while pedaling on a stationary bike or relaxing (i.e., no pedaling). We set them four conditions, namely, (1) performing only the oddball task (i.e., control), (2) performing the oddball task while pedaling at optimal cadence (i.e., optimal), (3) performing the oddball task while pedaling faster than optimal cadence (i.e., fast), and (4) performing the oddball task while pedaling slower than optimal cadence (i.e., slow). P300 amplitudes at Cz and Pz electrodes under optimal, fast, and slow conditions were significantly lower than those under control conditions. P300 amplitudes at Pz under fast and slow conditions were significantly lower than those under the optimal condition. No significant changes in P300 latency at any electrode were observed under any condition. Our findings revealed that pedaling at non-optimal cadence results in less attention being paid to external stimuli compared with pedaling at optimal cadence.

Muscle synergies are modified with improved task performance in skill learning.

How do muscle synergies change as motor skills are learned? The purpose of this study was to investigate the relationship between synergy number and skill acquisition, and to examine learning-related changes in synergy structure and activation patterns. We performed muscle synergy analysis using non-negative matrix factorization to identify muscle synergies from activation patterns of ten major leg muscles before and after recreational cyclists learned a novel one-legged pedal force aiming task (Park, Van Emmerik, & Caldwell, 2021). Synergy number was defined as the smallest number of factors from the matrix factorization algorithm that could explain more than the predefined threshold values. Improvements in pedal force direction after practice occurred without a change in the number of muscle synergies (four), suggesting that task constraints (e.g. the need for smooth pedaling motion) in this novel targeting task may limit the CNS to the same number of muscle synergies before and after practice. Improved task performance while continuing to satisfy multiple biomechanical tasks was obtained with changes in structure (muscle weightings) for one synergy, and activation amplitudes without changes in timing or pattern for three synergies. In each crank cycle quadrant, multiple synergies were altered in either structure or activation amplitude, suggesting that the cooperative changes may be essential for improving task performance while producing a smooth pedaling motion. Changes in both synergy structure and activation levels could be muscle coordination strategies in motor skill learning.

Accelerated Muscle Deoxygenation in Aerobically Fit Subjects During Exhaustive Exercise Is Associated With the ACE Insertion Allele.

Introduction: The insertion/deletion (I/D) polymorphism in the gene for the major regulator of vascular tone, angiotensin-converting enzyme-insertion/deletion (ACE-I/D) affects muscle capillarization and mitochondrial biogenesis with endurance training. We tested whether changes of leg muscle oxygen saturation (SmO2) during exhaustive exercise and recovery would depend on the aerobic fitness status and the ACE I/D polymorphism. Methods: In total, 34 healthy subjects (age: 31.8 ± 10.2 years, 17 male, 17 female) performed an incremental exercise test to exhaustion. SmO2 in musculus vastus lateralis (VAS) and musculus gastrocnemius (GAS) was recorded with near-IR spectroscopy. Effects of the aerobic fitness status (based on a VO2peak cutoff value of 50 ml O2 min-1 kg-1) and the ACE-I/D genotype (detected by PCR) on kinetic parameters of muscle deoxygenation and reoxygenation were assessed with univariate ANOVA. Results: Deoxygenation with exercise was comparable in VAS and GAS (p = 0.321). In both leg muscles, deoxygenation and reoxygenation were 1.5-fold higher in the fit than the unfit volunteers. Differences in muscle deoxygenation, but not VO2peak, were associated with gender-independent (p > 0.58) interaction effects between aerobic fitness × ACE-I/D genotype; being reflected in a 2-fold accelerated deoxygenation of VAS for aerobically fit than unfit ACE-II genotypes and a 2-fold higher deoxygenation of GAS for fit ACE-II genotypes than fit D-allele carriers. Discussion: Aerobically fit subjects demonstrated increased rates of leg muscle deoxygenation and reoxygenation. Together with the higher muscle deoxygenation in aerobically fit ACE-II genotypes, this suggests that an ACE-I/D genotype-based personalization of training protocols might serve to best improve aerobic performance.

Can passive pedaling improve sexual function in patients under hemodialysis? A randomized clinical trial.

To investigate the effect of passive pedaling with mini bike on sexual function in patients under hemodialysis. This study was a randomized clinical trial. Thirty-seven patients undergoing hemodialysis were assigned to the intervention (n = 20) and control (n = 17) groups by the stratified block randomization method. The intervention group exercised with a mini bike that was automatic and tuned for patients during the first 2 h of dialysis, twice a week for 20 min each time, for 3 months. The International Index of Erectile Function and Female Sexual Function Index were used to assess the sexual function in the first, second, and third months during the intervention and one month after the intervention. A higher score indicates a better sexual function. Repeated measure ANOVA, Chi-square and Fisher exact tests, independent t, and Mann-Whitney U tests were used for data analysis. The SPSS software version 22 was used for data analysis. Sexual function scores of the intervention group were 35.9 at the beginning of the study, 34.1 in the first month, 37.4 in the second month, 34.8 in the third month, and 31.7 one month after the study. There was no significant difference in the scores of sexual function in the intervention group during the study. The mean scores of sexual function in the control group were 34.5, 34.4, 34.9, 33.8, and 33.9 at the beginning of the study, in the first month, in the second month, in the third month, and one month after the study, respectively (p > 0.05). There was no significant difference between the two groups in terms of sexual function scores during and after the intervention (p > 0.05). Passive pedaling with mini-bike had no effect on sexual function of hemodialysis patients.