Effect of footwear on intramuscular EMG activity of plantar flexor muscles in walking

One of the purposes of footwear is to assist locomotion, but some footwear types seem to restrict natural foot motion, which may affect the contribution of ankle plantar flexor muscles to propulsion. This study examined the effects of different footwear conditions on the activity of ankle plantar flexors during walking. Ten healthy habitually shod individuals walked overground in shoes, barefoot and in flip-flops while fine-wire electromyography (EMG) activity was recorded from flexor hallucis longus (FHL), soleus (SOL), and medial and lateral gastrocnemius (MG and LG) muscles. EMG signals were peak-normalised and analysed in the stance phase using Statistical Parametric Mapping (SPM). We found highly individual EMG patterns. Although walking with shoes required higher muscle activity for propulsion than walking barefoot or with flip-flops in most participants, this did not result in statistically significant differences in EMG amplitude between footwear conditions in any muscle (p > 0.05). Time to peak activity showed the lowest coefficient of variation in shod walking (3.5, 7.0, 8.0 and 3.4 for FHL, SOL, MG and LG, respectively). Future studies should clarify the sources and consequences of individual EMG responses to different footwear.     

The effect of lower-limb prosthetic alignment on muscle activity during sit-to-stand

People with a transtibial amputation (TTA) have altered motion during daily tasks, which may be influenced by prosthetic alignment. This study aimed to determine the effect of medial/lateral prosthetic alignment shifts on muscle activity, measured by integrated electromyography (iEMG), and to compare muscle activity between people with and without TTA during sit-to-stand. We quantified ground reaction forces and three-dimensional center-of-mass position to interpret muscle activity results. Compared to the prescribed alignment, the bilateral knee extensors had greater activity in the medial alignment (p < 0.001) and the amputated side gluteus medius and less activity in the lateral alignment (p = 0.035), which may be a result of altered muscular requirements for postural control. In people with TTA, smaller intact side gluteus medius activity was associated with frontal plane motion of the center-of-mass, which was not observed in non-amputees. Compared to non-amputees, people with TTA had greater iEMG in the intact side tibialis anterior (p = 0.031) and amputated side rectus femoris (p < 0.001), which may be required to brake the body center-of-mass in the absence of amputated side tibialis anterior. These results suggest that lateral alignment shifts may reduce muscle activity during sit-to-stand for people with TTA and emphasize the importance of analyzing sit-to-stand in three dimensions.     

Surface EMG variability while running on grass,concrete and treadmill

This study aimed to investigate whether inter-trial variability in muscle activity (electromyography, EMG) during running is influenced by the number of acquired steps and running surface. Nine healthy participants ran at preferred speed on treadmill, concrete, and grass. Tibial acceleration and surface EMG from 12 lower limb muscles were recorded. The coefficient of variation (CV) from the average EMG and peak EMG were computed from 5, 10, 25, 50 and 100 steps in each running surface. Data average stability was computed using sequential estimation technique (SET) from 100 steps. The CV for average and peak EMG was lower during treadmill running compared to running on grass (−11 ± 2.88%) or concrete (−9 ± 2.94%) (p < 0.05), without differences across the different number of steps. Moreover, the peak EMG CV from peroneus longus was lower on concrete (p < 0.05), whereas gluteus maximus presented greater variability on grass compared to concrete (p < 0.05). The SET analysis revealed that average stability is reached with up to 10 steps across all running conditions. Therefore, treadmill running induced greater variability compared to overground, without influence of the number of steps on EMG variability. Moreover, average stability for EMG recordings may be reached with up to 10 steps.     

A comparison of muscle activity of the dominant and non-dominant side of the body during low versus high loaded bench press exercise performed to muscular failure

The main aim of the study was to compare the peak surface electromyography (sEMG) amplitude of muscles during low and high loaded bench press exercises performed to muscular failure on the dominant and non-dominant body side. Ten resistance-trained healthy males with at least six-year experience in resistance training (27.7 ± 5.6 years, 81.1 ± 5.8 kg and 175.3 ± 5.2 cm, bench press one-repetition maximum [1RM] = 98.9 ± 7.1 kg) performed the bench press at 50% and at 90%1RM. The differences in peak sEMG amplitude between body-sides and the external loads were recorded for the pectoralis major (PM), anterior deltoid (AD), and the long head of the triceps brachii (TB) during each attempt. A two-way repeated-measures ANOVAs revealed statistically significant main effect of side for AD (p < 0.001) and TB (p < 0.001) but not for PM (p = 0.168) and a significant main effect of load for TB (p < 0.001) but not for AD and PM (p = 0.229; p = 0.072; respectively). The post-hoc analysis for the main effect of side showed significantly higher peak sEMG amplitude for the dominant side compared to the non-dominant side for AD and TB at 50%1RM and 90%1RM (p < 0.001; all) with no statistically significant differences for PM (p = 0.187; p = 0.155; both loads). The post-hoc analysis for the main effect of load for TB revealed a significantly higher peak sEMG amplitude at 90%1RM compared to the 50%1RM (p = 0.009). The obtained results indicate that regardless of the external load, the peak sEMG activity of the AD, PM, and TB during the bench press exercise performed to muscular failure was higher on the dominant body-side.     

Biomechanics of overground vs. treadmill walking in healthy individuals.

The goal of this study was to compare treadmill walking with overground walking in healthy subjects with no known gait disorders. Nineteen subjects were tested, where each subject walked on a split-belt instrumented treadmill as well as over a smooth, flat surface. Comparisons between walking conditions were made for temporal gait parameters such as step length and cadence, leg kinematics, joint moments and powers, and muscle activity. Overall, very few differences were found in temporal gait parameters or leg kinematics between treadmill and overground walking. Conversely, sagittal plane joint moments were found to be quite different, where during treadmill walking trials, subjects demonstrated less dorsiflexor moments, less knee extensor moments, and greater hip extensor moments. Joint powers in the sagittal plane were found to be similar at the ankle but quite different at the knee and hip joints. Differences in muscle activity were observed between the two walking modalities, particularly in the tibialis anterior throughout stance, and in the hamstrings, vastus medialis and adductor longus during swing. While differences were observed in muscle activation patterns, joint moments and joint powers between the two walking modalities, the overall patterns in these behaviors were quite similar. From a therapeutic perspective, this suggests that training individuals with neurological injuries on a treadmill appears to be justified.     

Leg intramuscular pressures during locomotion in humans

To assess the usefulness of intramuscularpressure (IMP) measurement for studying muscle function during gait,IMP was recorded in the soleus and tibialis anterior muscles of 10 volunteers during treadmill walking and running by usingtransducer-tipped catheters. Soleus IMP exhibited single peaks duringlate-stance phase of walking [181 ± 69 (SE) mmHg] andrunning (269 ± 95 mmHg). Tibialis anterior IMP showed a biphasicresponse, with the largest peak (90 ± 15 mmHg during walking and151 ± 25 mmHg during running) occurring shortly after heel strike.IMP magnitude increased with gait speed in both muscles. Linearregression of soleus IMP against ankle joint torque obtained by adynamometer produced linear relationships (n = 2, r = 0.97 for both). Application ofthese relationships to IMP data yielded estimated peak soleus momentcontributions of 0.95-1.65 N · m/kgduring walking, and 1.43-2.70 N · m/kg during running. Phasic elevations of IMP during exercise are probably generated by local muscle tissue deformations due to muscle force development. Thus profiles of IMP provide a direct, reproducible indexof muscle function during locomotion in humans.

     

Detection of surface electromyography recording time interval without muscle fatigue effect for biceps brachii muscle during maximum voluntary contraction

The effects of fatigue on maximum voluntary contraction (MVC) parameters were examined by using force and surface electromyography (sEMG) signals of the biceps brachii muscles (BBM) of 12 subjects. The purpose of the study was to find the sEMG time interval of the MVC recordings which is not affected by the muscle fatigue. At least 10 s of force and sEMG signals of BBM were recorded simultaneously during MVC. The subjects reached the maximum force level within 2 s by slightly increasing the force, and then contracted the BBM maximally. The time index of each sEMG and force signal were labeled with respect to the time index of the maximum force (i.e. after the time normalization, each sEMG or force signal’s 0 s time index corresponds to maximum force point). Then, the first 8 s of sEMG and force signals were divided into 0.5 s intervals. Mean force, median frequency (MF) and integrated EMG (iEMG) values were calculated for each interval. Amplitude normalization was performed by dividing the force signals to their mean values of 0 s time intervals (i.e. ?0.25 to 0.25 s). A similar amplitude normalization procedure was repeated for the iEMG and MF signals. Statistical analysis (Friedman test with Dunn’s post hoc test) was performed on the time and amplitude normalized signals (MF, iEMG). Although the ANOVA results did not give statistically significant information about the onset of the muscle fatigue, linear regression (mean force vs. time) showed a decreasing slope (Pearson-r = 0.9462, p < 0.0001) starting from the 0 s time interval. Thus, it might be assumed that the muscle fatigue starts after the 0 s time interval as the muscles cannot attain their peak force levels. This implies that the most reliable interval for MVC calculation which is not affected by the muscle fatigue is from the onset of the EMG activity to the peak force time. Mean, SD, and range of this interval (excluding 2 s gradual increase time) for 12 subjects were 2353, 1258 ms and 536–4186 ms, respectively. Exceeding this interval introduces estimation errors in the maximum amplitude calculations of MVC–sEMG studies for BBM. It was shown that, simultaneous recording of force and sEMG signals was required to calculate the maximum amplitude of the MVC–sEMG more accurately.     

The effect of heel lifts on trunk muscle activation during gait: A study of young healthy females

Heel lifts are a treatment option for low back pain (LBP), whilst high-heeled shoes have been linked to LBP development. This study evaluated the effects of in-shoe 20 mm high bilateral heel lifts on trunk muscle activity. Activity of the erector spinae (ErSp), internal oblique and external oblique muscles was evaluated using surface electromyography in 15 young (20.7 ± 0.9 years) healthy female participants. Measures were taken during overground gait, both immediately and following two days habituation to the heel lifts. Immediately following the addition of the heel lifts, levels of ErSp muscle activity in the 5% epoch following heel strike increased by 19.2% (p < 0.05). Following habituation, levels of ErSp muscle activity in the 5% epoch prior to heel strike increased by 24.1% (p < 0.05), and a 14 ms (p < 0.001) earlier onset of ErSp muscle activity prior to heel strike was observed. These results indicate the heel lifts altered muscle activity reactively around heel strike (i.e. greater activity after heel strike) immediately after application and proactively (i.e. earlier onsets and greater activity prior to heel strike) after short term habituation. When put in context of previous research on trunk muscle activity in LBP populations, these changes may be important considerations for the aetiology, treatment and prevention of LBP.     

Limb and sex-related differences in knee muscle co-contraction exist 3 months after anterior cruciate ligament reconstruction

Interlimb and sex-based differences in gait mechanics and neuromuscular control are common after anterior cruciate ligament reconstruction (ACLR). Following ACLR, individuals typically exhibit elevated co-contraction of knee muscles, which may accelerate knee osteoarthritis (OA) onset. While directed (medial/lateral) co-contractions influence tibiofemoral loading in healthy people, it is unknown if directed co-contractions are present early after ACLR and if they differ across limbs and sexes. The purpose of this study was to compare directed co-contraction indices (CCIs) of knee muscles in both limbs between men and women after ACLR. Forty-five participants (27 men) completed overground walking at a self-selected speed 3 months after ACLR during which quadriceps, hamstrings, and gastrocnemii muscle activities were collected bilaterally using surface electromyography. CCIs of six muscle pairs were calculated during the weight acceptance interval. The CCIs of the vastus lateralis/biceps femoris muscle pair (lateral musculature) was greater in the involved limb (vs uninvolved; p = 0.02). Compared to men, women exhibited greater CCIs in the vastus medialis/lateral gastrocnemius and vastus lateralis/lateral gastrocnemius muscle pairs (p < 0.01 and p = 0.01, respectively). Limb- and sex-based differences in knee muscle co-contractions are detectable 3 months after ACLR and may be responsible for altered gait mechanics.     

Dynamic gait stability of treadmill versus overground walking in young adults

Treadmill has been broadly used in laboratory and rehabilitation settings for the purpose of facilitating human locomotion analysis and gait training. The objective of this study was to determine whether dynamic gait stability differs or resembles between the two walking conditions (overground vs. treadmill) among young adults. Fifty-four healthy young adults (age: 23.9 ± 4.7 years) participated in this study. Each participant completed five trials of overground walking followed by five trials of treadmill walking at a self-selected speed while their full body kinematics were gathered by a motion capture system. The spatiotemporal gait parameters and dynamic gait stability were compared between the two walking conditions. The results revealed that participants adopted a “cautious gait” on the treadmill compared with over ground in response to the possible inherent challenges to balance imposed by treadmill walking. The cautious gait, which was achieved by walking slower with a shorter step length, less backward leaning trunk, shortened single stance phase, prolonged double stance phase, and more flatfoot landing, ensures the comparable dynamic stability between the two walking conditions. This study could provide insightful information about dynamic gait stability control during treadmill ambulation in young adults.     

Walking speed effects on the lower limb electromyographic variability of healthy children aged 7–16 years

The evaluation of surface electromyography (sEMG) is commonly performed in children with cerebral palsy (CP) and reliable interpretation necessitates knowledge of the variability in age-matched, typically developing (TD) children. Variance ratio was calculated for inter-trial sEMG linear envelope (LE) and the Instantaneous Mean Frequency (IMNF) variability in the lower limb muscle in TD children, in three different age groups during slow, comfortable speed, and fast walking. Significantly greater variability was found in the 7–9 group compared to the 13–16 years. Variability during both slow and fast walking was significantly greater compared to comfortable speed walking and was profound in the 7–9 year age group. Variability of the IMNF was significantly greater than LE in the Tibialis-Anterior, Biceps-Femoris (BF), Vastus-Lateralis (VL), and Rectus-Femoris (RF). Clinical implications are that children under 10 years are more variable than older children when walking either slower or faster than self-selected walking speed. This suggests that muscle activation patterns in gait mature at a later stage of childhood than do kinematic gait patterns. Greater precaution, therefore, is needed when comparing sEMG patterns of less than 10 years of age patient and TD children.     

A new parameter for quantifying the variability of surface electromyographic signals during gait: The occurrence frequency

Natural variability of myoelectric activity during walking was recently analyzed considering hundreds of strides. This allowed assessing a parameter seldom considered in classic surface EMG (sEMG) studies: the occurrence frequency, defined as the frequency each muscle activation occurs with, quantified by the number of strides when a muscle is recruited with that specific activation modality. Aim of present study was to propose the occurrence frequency as a new parameter for assessing sEMG-signal variability during walking. Aim was addressed by processing sEMG signals acquired from Gastrocnemius Lateralis, Tibialis Anterior, Rectus Femoris and Biceps femoris in 40 healthy subjects in order to: (1) show that occurrence frequency is not correlated with ON/OFF instants (R_mean = 0.11 ± 0.07; P > 0.05) and total time of activation (R_mean = 0.15 ± 0.08; P > 0.05); (2) confirm the above results by two handy examples of application (analysis of gender and age) which highlighted that significant (P < 0.05) gender-related and age-related differences within population were detected in occurrence frequency, but not in temporal sEMG parameters. In conclusion, present study demonstrated that occurrence frequency is able to provide further information, besides those supplied by classical temporal sEMG parameters and thus it is suitable to complement them in the evaluation of variability of myoelectric activity during walking.     

Altered EMG patterns in diabetic neuropathic and not neuropathic patients during step ascending and descending

Diabetic peripheral neuropathy (DPN) causes motor control alterations during daily life activities. Tripping during walking or stair climbing is the predominant cause of falls in the elderly subjects with DPN and without (NoDPN). Surface Electromyography (sEMG) has been shown to be a valid tool for detecting alterations of motor functions in subjects with DPN. This study aims at investigating the presence of functional alterations in diabetic subjects during stair climbing and at exploring the relationship between altered muscle activation and temporal parameter. Lower limb muscle activities, temporal parameters and speed were evaluated in 50 subjects (10 controls, 20 with DPN, 20 without DPN), while climbing up and down a stair, using sEMG, three-dimentional motion capture and force plates. Magnitude and timing of sEMG linear envelopes peaks were extracted. Level walking was used as reference condition for the comparison with step negotiation. sEMG, speed and temporal parameters revealed significant differences among all groups of patients. Results showed an association between earlier activation of lower limb muscles and reduced speed in subjects with DPN. Speed and temporal parameters significantly correlated with sEMG (p < 0.05). The findings of this study are encouraging and could be used to improve rehabilitation programs aiming at reducing falls risk in diabetic subjects.     

Cardiovascular responses during spontaneous overground locomotion in freely moving decerebrate cats

Sadamoto, Tomoko, and Kanji Matsukawa. Cardiovascularresponses during spontaneous overground locomotion in freely movingdecerebrate cats. J. Appl. Physiol.83(5): 1454-1460, 1997.To examine whether the cerebrum isessential for producing the rapid cardiovascular adjustment at thebeginning of overground locomotion, we examined heart rate (HR), meanarterial blood pressure (MAP), and integrated electromyogram (iEMG) ofthe forelimb triceps brachialis muscle in freely moving decerebratecats during locomotion. Two to four days after decerebration surgeryperformed at the level of the precollicular-premammillary body, theanimals spontaneously produced coordinated overground locomotion,supporting body weight. HR began to increase immediately before theonset of iEMG, and MAP began to rise almost simultaneously with theiEMG onset. Their increases in HR and MAP (24 ± 3 beats/min and 22 ± 4 mmHg) were sustained during locomotion. Sinoaortic denervation(SAD) did not affect the abrupt changes in HR and MAP at the beginningof locomotion (0-4 s from the onset of iEMG), whereas SAD had acontrasting effect during the subsequent period, a decrease in the HRresponse (9 ± 1 beats/min) and an increase in the MAP response (30 ± 3 mmHg). These results suggest that the cerebrum and the rostral part of the diencephalon are not essential for producing the rapid cardiovascular adjustment at the beginning of spontaneous overground locomotion. The arterial baroreflex does not contribute to this rapidadjustment but plays an important role in regulating the cardiovascularresponses during the later period of spontaneous locomotion.

     

Reliability and minimal detectable change in scapulothoracic neuromuscular activity

Alterations in scapular muscle activity, including excess activation of the upper trapezius (UT) and onset latencies of the lower trapezius (LT) and serratus anterior (SA) muscles, are associated with abnormal scapular motion and shoulder impingement. Limited information exists on the reliability of neuromuscular activity to demonstrate the efficacy of interventions. The purpose of this study was to characterize the reproducibility of scapular muscle activity (mean activity, relative onset timing) over time and establish the minimal detectable change (MDC). Surface electromyography (sEMG) of the UT, LT, SA and anterior deltoid (AD) muscles in 16 adults were captured during an overhead lifting task in two sessions, one-week apart. sEMG data were also normalized to maximum isometric contraction and the relative onset and mean muscle activity during concentric and eccentric phases of the scapular muscles were calculated. Additionally, reliability of the absolute sEMG data during the lifting task and MVIC was evaluated. Both intrasession and intersession reliability of normalized and absolute mean scapular muscle activity, assessed with intraclass correlation coefficients (ICC), ranged from 0.62 to 0.99; MDC values were between 1.3% and 11.7% MVIC and 24 to 135 mV absolute sEMG. Reliability of sEMG during MVIC was ICC = 0.82–0.99, with the exception of intersession upper trapezius reliability (ICC = 0.36). Within session reliability of muscle onset times was ICC = 0.88–0.97, but between session reliability was lower with ICC = 0.43–0.73; MDC were between 39 and 237 ms. Small changes in scapular neuromuscular mean activity (>11.7% MVIC) can be interpreted as meaningful change, while change in muscle onset timing in light of specific processing parameters used in this study is more variable.     

Walking speed changes in response to novel user-driven treadmill control

Implementing user-driven treadmill control in gait training programs for rehabilitation may be an effective means of enhancing motor learning and improving functional performance. This study aimed to determine the effect of a user-driven treadmill control scheme on walking speeds, anterior ground reaction forces (AGRF), and trailing limb angles (TLA) of healthy adults. Twenty-three participants completed a 10-m overground walking task to measure their overground self-selected (SS) walking speeds. Then, they walked at their SS and fastest comfortable walking speeds on an instrumented split-belt treadmill in its fixed speed and user-driven control modes. The user-driven treadmill controller combined inertial-force, gait parameter, and position based control to adjust the treadmill belt speed in real time. Walking speeds, peak AGRF, and TLA were compared among test conditions using paired t-tests (α = 0.05). Participants chose significantly faster SS and fast walking speeds in the user-driven mode than the fixed speed mode (p > 0.05). There was no significant difference between the overground SS walking speed and the SS speed from the user-driven trials (p < 0.05). Changes in AGRF and TLA were caused primarily by changes in walking speed, not the treadmill controller. Our findings show the user-driven treadmill controller allowed participants to select walking speeds faster than their chosen speeds on the fixed speed treadmill and similar to their overground speeds. Since user-driven treadmill walking increases cognitive activity and natural mobility, these results suggest user-driven treadmill control would be a beneficial addition to current gait training programs for rehabilitation.     

Cross-correlations between gluteal muscle thickness derived from ultrasound imaging and hip biomechanics during walking gait

Ultrasound imaging (USI) of muscle thickness offers different insights into musculoskeletal function than kinematics, kinetics, and surface electromyography (sEMG), however it is unknown how USI-derived measures correlate to traditional measures during walking. The purpose of this study was to compare USI-derived gluteus maximus (GMAX) and medius (GMED) thickness measures to tri-planar hip kinematics and kinetics, and GMED thickness to sEMG amplitude. Fourteen females walked on a treadmill at 1.34 m/s. GMAX and GMED thickness, hip tri-planar kinematics, kinetics, and GMED sEMG were simultaneously recorded. USI-derived thickness measures were compared to other biomechanical outcomes using cross-correlation analyses, computed at each 1% (11-ms) of the gait cycle with lag times from −20% to 20%. GMED and GMAX thickness measures were most strongly correlated with hip extension and abduction angles at 150–220-ms lags (cross-correlation coefficients [CCF]: −0.34; −0.83). GMED thickness was most correlated to abduction and external rotation moments simultaneously (CCF: −0.28; −0.47). GMAX thickness and flexion moments were most strongly correlated at a 66-ms lag (CCF: 0.33). GMED sEMG amplitude was most strongly correlated to muscle thickness at a 99-ms lag (CCF: 0.39). These results elucidate the unique information provided from USI-derived measures of gluteal muscle thickness during walking.     

Lower limb joint stiffness and muscle co-contraction adaptations to instability footwear during locomotion

Unstable shoes (US) continually perturb gait which can train the lower limb musculature, but muscle co-contraction and potential joint stiffness strategies are not well understood. A shoe with a randomly perturbing midsole (IM) may enhance these adaptations. This study compares ankle and knee joint stiffness, and ankle muscle co-contraction during walking and running in US, IM and a control shoe in 18 healthy females. Ground reaction forces, three-dimensional kinematics and electromyography of the gastrocnemius medialis and tibialis anterior were recorded. Stiffness was calculated during loading and propulsion, derived from the sagittal joint angle-moment curves. Ankle co-contraction was analysed during pre-activation and stiffness phases. Ankle stiffness reduced and knee stiffness increased during loading in IM and US whilst walking (ankle, knee: p = 0.008, 0.005) and running (p < 0.001; p = 0.002). During propulsion, the opposite joint stiffness re-organisation was found in IM whilst walking (both joints p < 0.001). Ankle co-contraction increased in IM during pre-activation (walking: p = 0.001; running: p < 0.001), and loading whilst walking (p = 0.003), not relating to ankle stiffness. Results identified relative levels of joint stiffness change in unstable shoes, providing new evidence of how stability is maintained at the joint level.     

Intramuscular fine-wire electromyography during cycling: Repeatability,normalisation and a comparison to surface electromyography

This study investigated (a) the feasibility and repeatability of intramuscular fine-wire electromyographic (fEMG) recordings from leg muscles during the repetitive, high-velocity cycling movement, (b) the influence of amplitude normalization technique on repeatability and statistical sensitivity, (c) the influence of test-retest interval duration on repeatability, and (d) differences between fEMG and surface EMG (sEMG) recordings of cycling. EMG activity of leg muscles was recorded using surface and fine-wire electrodes during one (n = 12, to investigate statistical sensitivity and compare sEMG and fEMG) or two sessions (T1 and T2, 5–20 days apart, n = 10, to investigate repeatability). fEMG recordings were feasible and there was high repeatability of fEMG recordings normalised to maximum measured EMG amplitude (MAX); mean coefficients of multiple correlation (CMC) ranged from .83 ± .13 to .88 ± .07. Data normalised to maximal (MVC) or submaximal contractions (sMVC) were less repeatable (p < .01). Statistical sensitivity was also greatest for data normalised to MAX (p < .01). Repeatability of fEMG increased with greater test-retest intervals (p < .01). The global pattern of muscle recruitment was consistent between sEMG and fEMG but sEMG recordings were characterized by additional myoelectric content. These findings support and guide the use of fEMG techniques to investigate leg muscle recruitment during cycling.