Changes in force and tendinous tissue elongation during the early phase of tetanic summation in in vivo human tibialis anterior muscle

The purpose of this study was to determine the changes that occur in tendinous tissue properties during the early phase of tetanic summation in the in vivo human tibialis anterior muscle (TA). The torque response and tendinous tissue elongation following single stimuli, two-pulse trains, and three-pulse trains were recorded in the TA during isometric contractions. The elongation, compliance, and lengthening velocity of tendinous tissue were determined by real-time ultrasonography. The contribution of the response to the second stimulation (C2) was obtained by subtracting the response to the single stimulation (C1) from the response of doublet. The third contribution (C3) was obtained by subtracting the response to the doublet from that of the triplet. C2 (7.8±0.5 Nm) and C3 (7.3±0.6 Nm) had torque responses significantly higher than C1 (3.6±0.7 Nm). In contrast, the elongations of tendinous tissue for C2 (2.8±0.4 mm) and C3 (1.7±0.2 mm) were significantly lower than for C1 (4.9±0.3 mm), indicating that the summation pattern of tendinous tissue elongation is different from the summation pattern of torque response. In addition, this showed considerable difference both between C1 (0.12±0.01 mm/N; 83±4.6 mm/s) and C2 (0.03±0.005 mm/N; 50±6.3 mm/s) and between C1 and C3 (0.02±0.002 mm/N; 39±6.4 mm/s) in the compliance and lengthening velocity of tendinous tissue. These results suggest that changes in tendinous tissue properties between first and second contraction are related to different summation patterns of force and tendinous tissue elongation during early phase of tetanic summation.     

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.     

Extra-torque of human tibialis anterior during electrical stimulation with linearly varying frequency and amplitude trains

This work aimed to characterise the whole human muscle input/output law during electrical stimulation with triangular varying frequency and amplitude trains through combined analysis of torque, mechanomyogram (MMG) and electromyogram (EMG).The tibialis anterior (TA) of ten subjects (age 23–35 years) was investigated during static contraction obtained through neuromuscular electrical stimulation. After potentiation, TA underwent two 15 s stimulation patterns: (a) frequency triangle (FT): 2 > 35 > 2 Hz at Vmax (amplitude providing full motor unit recruitment); (b) amplitude triangle (AT): Vmin > Vmax > Vmin (Vmin providing TA least mechanical response) at 35 Hz. 2 > 35 Hz or Vmin > Vmax as well as 35 > 2 Hz or Vmax > Vmin were defined as up-going ramp (UGR) and down-going ramp (DGR), respectively. TA torque, MMG and EMG were detected by a load cell, an optical laser distance sensor and a probe with two silver bar electrodes, respectively. For both FT and AT, only the two mechanical signals resulted always larger in DGR than in UGR, during AT extra-torque and extra-MMG were present even in the first 1/3 of the amplitude range where EMG data presented no significant differences between DGR and UGR.Our data suggest that extra-torque and extra-displacement are evident for both FT and AT, being mainly attributed to an intrinsic muscle property.     

The effects of accelerometer placement on mechanomyographic amplitude and mean power frequency during cycle ergometry

The purposes of this study were threefold: (1) to compare the power output related patterns of absolute and normalized MMG amplitude and MPF responses for proximal and distal accelerometer placements on the vastus lateralis (VL) muscle during incremental cycle ergometry; (2) to examine the influence of accelerometer placements on mean absolute MMG amplitude and MPF values; and (3) to determine the effects of normalization on mean MMG amplitude and MPF values from proximal and distal accelerometer placements. Fifteen adults (10 men and 5 women; mean ± SD age = 23.9 ± 3.1 years) performed incremental cycle ergometry tests to exhaustion. Two accelerometers were placed proximal and distal on the VL muscle. Paired t-tests indicated that absolute MMG amplitude values for the proximal accelerometer were greater (p < 0.05) than the distal accelerometer at all power outputs. The normalized MMG amplitude also had greater values for the proximal accelerometer at all power outputs, except 50 W. There were no differences, however, between proximal and distal accelerometers for absolute MMG MPF, except at 75 W, and normalization eliminated this difference. Twenty-seven percent of the subjects exhibited different power output related patterns of responses between accelerometer placements for MMG amplitude and 47% exhibited different patterns for MPF. These findings indicated that normalization did not eliminate the influence of accelerometer placement on MMG amplitude and highlighted the importance of standardizing accelerometer placements to compare MMG values during cycle ergometry.     

Assessment of quadriceps muscle weakness in patients after total knee arthroplasty and total hip arthroplasty: Methodological issues

The aim of this exploratory study was to verify whether the evaluation of quadriceps muscle weakness is influenced by the testing modality (isometric vs. isokinetic vs. isoinertial) and by the calculation method (within-subject vs. between-subject comparisons) in patients 4–8 months after total knee arthroplasty (TKA, n = 29) and total hip arthroplasty (THA, n = 30), and in healthy controls (n = 19). Maximal quadriceps strength was evaluated as (1) the maximal voluntary contraction (MVC) torque during an isometric contraction, (2) the peak torque during an isokinetic contraction, and (3) the one repetition maximum (1-RM) load during an isoinertial contraction. Muscle weakness was calculated as the difference between the involved and the uninvolved side (within-subject comparison) and as the difference between the involved side of patients and controls (between-subject comparison). Muscle weakness estimates were not significantly affected by the calculation method (within-subject vs. between-subject; P > 0.05), whereas a significant main effect of testing modality (P < 0.05) was observed. Isometric MVC torque provided smaller weakness estimates than isokinetic peak torque (P = 0.06) and isoinertial 1-RM load (P = 0.008), and the clinical occurrence of weakness (proportion of patients with large strength deficits) was also lower for MVC torque. These results have important implications for the evaluation of quadriceps muscle weakness in TKA and THA patients 4–8 months after surgery.     

EMG normalization to study muscle activation in cycling

The value of electromyography (EMG) is sensitive to many physiological and non-physiological factors. The purpose of the present study was to determine if the torque–velocity test (T–V) can be used to normalize EMG signals into a framework of biological significance. Peak EMG amplitude of gluteus maximus (GMAX), vastus lateralis (VL), rectus femoris (RF), biceps femoris long head (BF), gastrocnemius medialis (GAS) and soleus (SOL) was calculated for nine subjects during isometric maximal voluntary contractions (IMVC) and torque–velocity bicycling tests (T–V). Then, the reference EMG signals obtained from IMVC and T–V bicycling tests were used to normalize the amplitude of the EMG signals collected for 15 different submaximal pedaling conditions. The results of this study showed that the repeatability of the measurements between IMVC (from 10% to 23%) and T–V (from 8% to 20%) was comparable. The amplitude of the peak EMG of VL was 99 ± 43% higher (p < 0.001) when measured during T–V. Moreover, the inter-individual variability of the EMG patterns calculated for submaximal cycling exercises differed significantly when using T–V bicycling normalization method (GMAX: 0.33 ± 0.16 vs. 1.09 ± 0.04, VL: 0.07 ± 0.02 vs. 0.64 ± 0.14, SOL: 0.07 ± 0.03 vs. 1.00 ± 0.07, RF: 1.21 ± 0.20 vs. 0.92 ± 0.13, BF: 1.47 ± 0.47 vs. 0.84 ± 0.11). It was concluded that T–V bicycling test offers the advantage to be less time and energy-consuming and to be as repeatable as IMVC tests to measure peak EMG amplitude. Furthermore, this normalization method avoids the impact of non-physiological factors on the amplitude of the EMG signals so that it allows quantifying better the activation level of lower limb muscles and the variability of the EMG patterns during submaximal bicycling exercises.     

Torque-onset determination: Unintended consequences of the threshold method

Background: Compared with visual torque-onset-detection (TOD), threshold-based TOD produces onset bias, which increases with lower torques or rates of torque development (RTD). Purpose: To compare the effects of differential TOD-bias on common contractile parameters in two torque-disparate groups. Methods: Fifteen boys and 12 men performed maximal, explosive, isometric knee-extensions. Torque and EMG were recorded for each contraction. Best contractions were selected by peak torque (MVC) and peak RTD. Visual-TOD-based torque-time traces, electromechanical delays (EMD), and times to peak RTD (tRTD) were compared with corresponding data derived from fixed 4-N m- and relative 5%MVC-thresholds. Results: The 5%MVC TOD-biases were similar for boys and men, but the corresponding 4-N m-based biases were markedly different (40.3 ± 14.1 vs. 18.4 ± 7.1 ms, respectively; p < 0.001). Boys–men EMD differences were most affected, increasing from 5.0 ms (visual) to 26.9 ms (4 N m; p < 0.01). Men’s visually-based torque kinetics tended to be faster than the boys’ (NS), but the 4-N m-based kinetics erroneously depicted the boys as being much faster to any given %MVC (p < 0.001). Conclusions: When comparing contractile properties of dissimilar groups, e.g., children vs. adults, threshold-based TOD methods can misrepresent reality and lead to erroneous conclusions. Relative-thresholds (e.g., 5% MVC) still introduce error, but group-comparisons are not confounded.     

The acute effects of local muscle vibration frequency on peak torque,rate of torque development,and EMG activity

PurposeVibratory stimuli enhance muscle activity and may be used for rehabilitation and performance enhancement. Efficacy of vibration varies with the frequency of stimulation, but the optimal frequency is unclear. The purpose of this study was to examine the effects of 30 Hz and 60 Hz local muscle vibration (LMV) on quadriceps function.MethodsTwenty healthy volunteers (age = 20.4 ± 1.4 years, mass = 68.1 ± 11.0 kg, height = 170.1 ± 8.8 cm, males = 9) participated. Isometric knee extensor peak torque (PT), rate of torque development (RTD), and electromyography (EMG) of the quadriceps were assessed followed by one of the three LMV treatments (30 Hz, 60 Hz, control) applied under voluntary contraction, and again immediately, 5, 15, and 30 min post-treatment in three counterbalanced sessions. Dependent variables were analyzed using condition by time repeated-measures ANOVA.ResultsThe condition × time interaction was significant for EMG amplitude (p = 0.001), but not for PT (p = 0.324) or RTD (p = 0.425). The increase in EMG amplitude following 30 Hz LMV was significantly greater than 60 Hz LMV and control.ConclusionsThese findings suggest that 30 Hz LMV may elicit an improvement in quadriceps activation and could be used to treat quadriceps dysfunction resulting from knee pathologies.     

Validity of the twitch interpolation technique for the assessment of quadriceps neuromuscular asymmetries

This study examined the validity of the twitch interpolation technique for evaluating side-to-side asymmetries in quadriceps neuromuscular function. Fifty-six subjects with a wide range of asymmetries (19 healthy, 24 with unilateral and 13 with bilateral anterior cruciate ligament reconstruction) took part in the study. Supramaximal electrical paired stimuli were delivered to the quadriceps muscle during and immediately after a maximal voluntary contraction (MVC) of the knee extensors (twitch interpolation technique). MVC torque, voluntary activation and resting doublet-evoked torque were measured separately for the two sides, and percent side-to-side asymmetries were calculated for each parameter. MVC torque asymmetry was plotted against voluntary activation asymmetry and doublet-evoked torque asymmetry, and a multiple regression analysis was also conducted. Significant positive correlations were observed between MVC torque asymmetry and both voluntary activation asymmetry (r = 0.40; p = 0.002) and doublet-evoked torque asymmetry (r = 0.53; p < 0.001), and their relative contribution to MVC torque asymmetry was comparable (r = 0.64; p < 0.001). These results establish the validity of the twitch interpolation technique for the assessment of neuromuscular asymmetries. This methodology could provide useful insights into the contribution of some neural and muscular mechanisms that underlie quadriceps strength deficits.     

Rapid torque development in older female fallers and nonfallers: A comparison across lower-extremity muscles

The objective of this study was to compare reaction time, joint torque, rate of torque development, and magnitude of neuromuscular activation of lower-extremity muscles in elderly female fallers and nonfallers. Participants included 11, elderly, female fallers (71.3 ± 5.4 years) and twelve nonfallers (71.3 ± 6.2 years) who completed a fall risk questionnaire. Then, maximal, voluntary, isometric contractions of the knee and ankle muscles were performed in reaction to a visual cue to determine joint torque, rate of torque development, reaction time, and nervous activation of agonists and antagonists. Results indicated that significantly more fallers reported “dizziness upon rising”, “use of balance altering medications”, “stress or depression”, “not enough sleep”, “arthritis in lower body”, “chronic pain in lower body”, and “tiring easily while walking” (all P < 0.05). Normalized dorsiflexion and plantarflexion strength scores (summation of peak torque, rate of torque development and impulse) were lower in fallers than in nonfallers (P < 0.05). When summed across lower-extremity muscle groups, fallers demonstrated 19% lower peak torque and 29% longer motor time (P < 0.05). In conclusion, comprehensive fall risk screening and prevention programs should address both neuromuscular and non-muscular factors, and, weakness of the ankle dorsiflexors and plantarflexors should be further studied as potential contributors to falls in older adults.     

Adaptations of upper trapezius muscle activity during sustained contractions in women with fibromyalgia

The study compared the distribution of electromyographic (EMG) signal amplitude in the upper trapezius muscle in 10 women with fibromyalgia and in 10 healthy women before and after experimentally-induced muscle pain. Surface EMG signals were recorded over the right upper trapezius muscle with a 10 × 5 grid of electrodes during 90° shoulder abduction sustained for 60 s. The control subjects repeated the abduction task following injections of isotonic and hypertonic (painful) saline into the upper trapezius muscle. The EMG amplitude was computed for each electrode pair and provided a topographical map of the distribution of muscle activity. The pain level rated by the patients at the beginning of the sustained contraction was 5.9 ± 1.5. The peak pain intensity for the control group following the injection of hypertonic saline was 6.0 ± 1.6. During the sustained contractions, the EMG amplitude increased relatively more in the cranial than caudal region of the upper trapezius muscle for the control subjects (shift in the distribution of EMG amplitude: 2.3 ± 1.3 mm; P < 0.01). The patient group showed lower average EMG amplitude than the controls during the contraction (P < 0.05) and did not show different changes in EMG amplitude between different regions of the upper trapezius. A similar behavior was observed for the control group following injection of hypertonic saline. The results indicate that muscle pain prevents the adaptation of upper trapezius activity during sustained contractions as observed in non-painful conditions, which may induce overuse of similar muscle compartments with fatigue.     

Electromyographic and mechanomyographic responses across repeated maximal isometric and concentric muscle actions of the leg extensors

The purpose of the present study was to examine the patterns of responses for torque, electromyographic (EMG) amplitude, EMG mean power frequency (MPF), mechanomyographic (MMG) amplitude, and MMG MPF across 30 repeated maximal isometric (ISO) and concentric (CON) muscle actions of the leg extensors. Twelve female subjects (21.1 ± 1.4 yrs; 63.3 ± 7.4 kg) performed ISO and CON fatigue protocols with EMG and MMG signals recorded from the vastus lateralis. The relationships for torque, EMG amplitude, EMG MPF, MMG amplitude, and MMG MPF versus repetition number were examined using polynomial regression. The results indicated there were decreases (p < 0.05) across the ISO muscle actions for torque (r² = 0.95), EMG amplitude (R² = 0.44), EMG MPF (r² = 0.62), and MMG MPF (r² = 0.48), but no change in MMG amplitude (r² = 0.07). In addition, there were decreases across the CON muscle actions for torque (R² = 0.97), EMG amplitude (R² = 0.46), EMG MPF (R² = 0.86), MMG amplitude (R² = 0.44), and MMG MPF (R² = 0.80). Thus, the current findings suggested that the mechanisms of fatigue and motor control strategies used to modulate torque production were similar between maximal ISO and CON muscle actions.     

Multiple nanosecond electric pulses increase the number but not the size of long-lived nanopores in the cell membrane

Exposure to intense, nanosecond-duration electric pulses (nsEP) opens small but long-lived pores in the plasma membrane. We quantified the cell uptake of two membrane integrity marker dyes, YO-PRO-1 (YP) and propidium (Pr) in order to test whether the pore size is affected by the number of nsEP. The fluorescence of the dyes was calibrated against their concentrations by confocal imaging of stained homogenates of the cells. The calibrations revealed a two-phase dependence of Pr emission on the concentration (with a slower rise at < 4 μM) and a linear dependence for YP. CHO cells were exposed to nsEP trains (1 to 100 pulses, 60 ns, 13.2 kV/cm, 10 Hz) with Pr and YP in the medium, and the uptake of the dyes was monitored by time-lapse imaging for 3 min. Even a single nsEP triggered a modest but detectable entry of both dyes, which increased linearly when more pulses were applied. The influx of Pr per pulse was constant and independent of the pulse number. The influx of YP per pulse was highest with 1- and 2-pulse exposures, decreasing to about twice the Pr level for trains from 5 to 100 pulses. The constant YP/Pr influx ratio for trains of 5 to 100 pulses suggests that increasing the number of pulses permeabilizes cells to a greater extent by increasing the pore number and not the pore diameter.     

Unchanged H-reflex during a sustained isometric submaximal plantar flexion performed with an EMG biofeedback

The aim of this study was to assess H-reflex plasticity and activation pattern of the plantar flexors during a sustained contraction where voluntary EMG activity was controlled via an EMG biofeedback. Twelve healthy males (28.0 ± 4.8 yr) performed a sustained isometric plantar flexion while instructed to maintain summed EMG root mean square (RMS) of gastrocnemius lateralis (GL) and gastrocnemius medialis (GM) muscles fixed at a target corresponding to 80% maximal voluntary contraction torque via an EMG biofeedback. Transcutaneous electrical stimulation of the posterior tibial nerve was evoked during the contraction to obtain the maximal H-reflex amplitude to maximal M-wave amplitude ratio (H_sup/M_sup ratio) from GL, GM and soleus (SOL) muscles. Neuromuscular function was also assessed before and immediately after exercise. Results showed a decrease in SOL activation during sustained flexion (from 65.5 ± 6.4% to 42.3 ± 3.8% maximal EMG, p < 0.001), whereas summed EMG RMS of GL and GM remained constant (59.7 ± 4.8% of maximal EMG on average). No significant change in the H_sup/M_sup ratio was found for SOL, GL and GM muscles. Furthermore, it appears that the decrease in maximal voluntary contraction torque (?20.4 ± 2.9%, p < 0.001) was related to both neural and contractile impairment. Overall, these findings indicate that the balance between excitation and inhibition affecting the motoneuron pool remains constant during a sustained contraction where myoelectrical activity is controlled via an EMG biofeedback or let free to vary.     

Validity of trunk extensor and flexor torque measurements using isokinetic dynamometry

This study aimed to evaluate the validity and test–retest reliability of trunk muscle strength testing performed with a latest-generation isokinetic dynamometer. Eccentric, isometric, and concentric peak torque of the trunk flexor and extensor muscles was measured in 15 healthy subjects. Muscle cross sectional area (CSA) and surface electromyographic (EMG) activity were respectively correlated to peak torque and submaximal isometric torque for erector spinae and rectus abdominis muscles. Reliability of peak torque measurements was determined during test and retest sessions. Significant correlations were consistently observed between muscle CSA and peak torque for all contraction types (r = 0.74−0.85; P < 0.001) and between EMG activity and submaximal isometric torque (r ⩾ 0.99; P < 0.05), for both extensor and flexor muscles. Intraclass correlation coefficients were comprised between 0.87 and 0.95, and standard errors of measurement were lower than 9% for all contraction modes. The mean difference in peak torque between test and retest ranged from −3.7% to 3.7% with no significant mean directional bias. Overall, our findings establish the validity of torque measurements using the tested trunk module. Also considering the excellent test–retest reliability of peak torque measurements, we conclude that this latest-generation isokinetic dynamometer could be used with confidence to evaluate trunk muscle function for clinical or athletic purposes.     

Electromyographic latency of postural evoked responses from the leg muscles during EquiTest Computerised Dynamic Posturography: Reference data on healthy subjects

No normative data are available for the latencies of the EMG signals from the ankle muscles in response to sudden sagittal tilt (toes-UP or toes-DOWN) or shift (shift-FOR or shift-BACK) of the support surface during standing. In this study the postural evoked response (PER) paradigm on the EquiTest™ force platform was applied to 31 healthy adults (18 women and 13 men; mean age 29 years). The EMG latencies (PEREMG) were computed both through the standard manual procedure and through a specially designed automated algorithm. The manually computed PEREMG onset yielded a 95% tolerance interval between 82 ms and 148 ms after toes-UP perturbation, between 93 ms and 182 ms after toes-DOWN perturbation, between 67 ms and 107 ms after shift-BACK perturbation, and between 73 ms and 113 ms after shift-FOR perturbation. When comparing the two methods, paired t-tests showed no significant mean difference (Bonferroni-adjusted p-values ranged from 0.440 to 1.000) and all Bland–Altman plots included zero difference within the limits of agreement. Therefore, the manual and the automated methods appear to be sufficiently consistent. These results foster the clinical application of PEREMG testing on the EquiTest platform.     

Tendon reflex is suppressed during whole-body vibration

In this study we have investigated the effect of whole body vibration (WBV) on the tendon reflex (T-reflex) amplitude. Fifteen young adult healthy volunteer males were included in this study. Records of surface EMG of the right soleus muscle and accelerometer taped onto the right Achilles tendon were obtained while participant stood upright with the knees in extension, on the vibration platform. Tendon reflex was elicited before and during WBV. Subjects completed a set of WBV. Each WBV set consisted of six vibration sessions using different frequencies (25, 30, 35, 40, 45, 50 Hz) applied randomly. In each WBV session the Achilles tendon was tapped five times with a custom-made reflex hammer. The mean peak-to-peak (PP) amplitude of T-reflex was 1139.11 ± 498.99 µV before vibration. It decreased significantly during WBV (p < 0.0001). The maximum PP amplitude of T-reflex was 1333 ± 515 μV before vibration. It decreased significantly during WBV (p < 0.0001). No significant differences were obtained in the mean acceleration values of Achilles tendon with tapping between before and during vibration sessions. This study showed that T-reflex is suppressed during WBV. T-reflex suppression indicates that the spindle primary afferents must have been pre-synaptically inhibited during WBV similar to the findings in high frequency tendon vibration studies.     

Electromyography responses of pediatric and young adult volunteers in low-speed frontal impacts

No electromyography (EMG) responses data exist of children exposed to dynamic impacts similar to automotive crashes, thereby, limiting active musculature representation in computational occupant biomechanics models. This study measured the surface EMG responses of three neck, one torso and one lower extremity muscles during low-speed frontal impact sled tests (average maximum acceleration: 3.8 g; rise time: 58.2 ms) performed on seated, restrained pediatric (n = 11, 8–14 years) and young adult (n = 9, 18–30 years) male subjects. The timing and magnitude of the EMG responses were compared between the two age groups. Two normalization techniques were separately implemented and evaluated: maximum voluntary EMG (MVE) and neck cross-sectional area (CSA). The MVE-normalized EMG data indicated a positive correlation with age in the rectus femoris for EMG latency; there was no correlation with age for peak EMG amplitudes for the evaluated muscles. The cervical paraspinous exhibited shorter latencies compared with the other muscles (2–143 ms). Overall, the erector spinae and rectus femoris peak amplitudes were relatively small. Neck CSA-normalized peak EMG amplitudes negatively correlated with age for the cervical paraspinous and sternocleidomastoid. These data can be useful to incorporate active musculature in computational models, though it may not need to be age-specific in low-speed loading environments.