Voluntary Isometric Contraction Force Research Articles

The Effects of Inorganic Nitrate Supplementation on Muscular Power and Endurance Across the Menstrual Cycle.

Oral inorganic nitrate (NO3-) supplementation increases nitric oxide (NO) bioavailability and may improve muscular power in males and females, although data in females is limited. Estrogen increases NO bioavailability and fluctuates throughout the menstrual cycle (MC), with low levels in the early follicular (EF) phase and peaking during the late follicular (LF) phase. The purpose of the present study was to examine the effects of NO3- supplementation on isokinetic peak power, maximal voluntary isometric contraction (MVIC) force, muscular endurance, and recovery from fatigue in healthy young females during the EF and LF phases of the MC. Ten eumenorrheic females were tested in a double-blinded, randomized, placebo-controlled design. Participants consumed ~13mmol NO3-, in the form of 140ml beetroot juice (BRJ), or an identical NO3--depleted placebo (PL), for ~5 days prior to visits and 2 hours prior to testing. Plasma estradiol was elevated in the LF phase, and plasma nitrite and nitrate were elevated in the BRJ condition (p < 0.05). While isokinetic peak power was unchanged, calculated maximal power (Pmax) and maximal velocity (Vmax) was significantly worsened in the BRJ treatment independent of the MC phase (p = 0.02 and 0.03, respectively). Muscular endurance, MVIC, and fatigue recovery were unaltered by BRJ or the MC. These data indicate that NO3- supplementation decreased maximal power and velocity in females and suggest that the benefits of NO3- supplementation previously found in males may not extend to young females.

The influence of Sex on the Effects of Inorganic Nitrate Supplementation on Muscular Power and Endurance.

Inorganic nitrate (NO3-) supplementation increases nitric oxide (NO) bioavailability and may improve muscular power and endurance, although most studies are in males. Therefore, the present double-blind, randomized, placebo-controlled study examined the effects of NO3- supplementation on isokinetic peak power, maximal voluntary isometric contraction (MVIC) force, muscular endurance (time-to-task failure; TTF), and recovery from fatigue in young females (n=12) and males (n=14). Participants consumed ~13mmol NO3- (BRJ), or an identical NO3--depleted beverage (PL), for ~3 days and 2 hours before testing visits. Plasma nitrate and nitrite were elevated in the BRJ condition (p ≤ 0.05). Peak power (W·kg-1) showed a sex effect (p ≤ 0.05) at all angular velocities and a sex-by-treatment effect at 270 and 360°/sec (p ≤ 0.05). Post hoc analysis revealed no significant differences between treatments (p > 0.05). Estimated maximal knee extension power (Pmax) and maximal knee extension velocity (Vmax) demonstrated no sex, treatment, or sex-by-treatment effect (p > 0.05). There were no significant effects for TTF (F: PL; 269±161 vs BRJ; 277±158s and M: PL; 228±171 vs BRJ; 194±100s; p > 0.05). Cohen's d effect sizes for peak power showed moderate to large effect sizes at 270 (d=0.92) and 360 deg/sec (d=0.81), showing a possible differentiated effect of dietary nitrate in females and males. The present data indicate that NO3- supplementation does not significantly affect knee extensor maximal power, maximal contraction velocity, and muscular endurance in either sex. The sex-dependent response to dietary nitrate supplementation requires further investigation as data on females is scarce.

Effects of slow dynamic, fast dynamic, and static stretching on recovery of performance, range of motion, balance, and joint position sense in healthy adults

IntroductionConsidering the effects of fatigue on athletic performance and the subsequent increase in the probability of injury, the purpose of this study was to compare the effects of slow dynamic, fast dynamic, and static stretching on the recovery of performance, range of motion (ROM), balance, and joint position sense.MethodsFifteen collegiate healthy females were involved in four separate sessions of slow dynamic stretching (SDS), fast dynamic stretching (FDS), static stretching (SS), and control condition (CC; without stretching), in a random order with at least 48 h of rest between sessions. After warming up, the individuals performed ROM, balance, joint position sense (JPS) maximum voluntary isometric contraction (MVIC) force as well as countermovement (CMJ) and squat jump (SJ) as pre-tests. After performing the knee fatigue protocol of 4 sets of knee extension and flexion at 60% of 1 repetition maximum (RM) to exhaustion (CC; without stretching) or stretching programs (SDS or FDS or SS), the subjects repeated all the tests at post-test 1 (after 5 min) and post-test 2 (after 60 min).ResultsA significantly lower JPS error was detected with SDS while JPS error increased in the SS and control conditions (p < 0.0001). MVIC force significantly increased with SDS and FDS but decreased in control and SS conditions (p < 0.0001). Moreover, a significant decrease in CMJ and SJ height in SS and control conditions was revealed (p < 0.0001). Also, a significant decrease in balance with the control condition was revealed. But only SDS minimized fatigue-induced balance decrements (p < 0.0001). Additionally, the control condition experienced a significant decrease in knee extensor ROM, which contrasted with the significant increase in the quadriceps flexibility with the stretching conditions.ConclusionsThe present results support the idea that SDS may increase quadriceps MVIC force, knee extensor ROM and knee JPS. So according to the present results, it is suggested that the SDS could be implemented and incorporated into a regular recovery program.

A dataset for fatigue estimation during shoulder internal and external rotation movements using wearables

Wearable sensors have recently been extensively used in sports science, physical rehabilitation, and industry providing feedback on physical fatigue. Information obtained from wearable sensors can be analyzed by predictive analytics methods, such as machine learning algorithms, to determine fatigue during shoulder joint movements, which have complex biomechanics. The presented dataset aims to provide data collected via wearable sensors during a fatigue protocol involving dynamic shoulder internal rotation (IR) and external rotation (ER) movements. Thirty-four healthy subjects performed shoulder IR and ER movements with different percentages of maximal voluntary isometric contraction (MVIC) force until they reached the maximal exertion. The dataset includes demographic information, anthropometric measurements, MVIC force measurements, and digital data captured via surface electromyography, inertial measurement unit, and photoplethysmography, as well as self-reported assessments using the Borg rating scale of perceived exertion and the Karolinska sleepiness scale. This comprehensive dataset provides valuable insights into physical fatigue assessment, allowing the development of fatigue detection/prediction algorithms and the study of human biomechanical characteristics during shoulder movements within a fatigue protocol.

The impact of cerebellar transcranial direct current stimulation on isometric bench press performance in trained athletes

Athletic development centers on optimizing performance, including technical skills and fundamental motor abilities such as strength and speed. Parameters such as maximum contraction force and rate of force development, influence athletic success, although performance gains become harder to achieve as athletic abilities increase. Non-invasive transcranial direct current stimulation of the cerebellum (CB-tDCS) has been used successfully to increase force production in novices, although the potential effects in athletes remain unexplored. The present study examined the effects of CB-tDCS on maximum isometric voluntary contraction force (MVCiso) and isometric rate of force development (RFDiso) during a bench press task in well-trained athletes. 21 healthy, male, strength-trained athletes participated in a randomized, sham-controlled, double-blinded crossover design. Each participant completed the isometric bench press (iBP) task on two separate days, with at least 5 days between sessions, while receiving either CB-tDCS or sham stimulation. Electromyography (EMG) recordings of three muscles involved in iBP were acquired bilaterally to uncover differences in neuromuscular activation and agonist-antagonist co-contraction between conditions. Contrary to our hypothesis, no significant differences in MVCiso and RFDiso were observed between CB-tDCS and sham conditions. Furthermore, no tDCS-induced differences in neuromuscular activation or agonist-antagonist co-contraction were revealed. Here, we argue that the effects of CB-tDCS on force production appear to depend on the individual's training status. Future research should study individual differences in tDCS responses between athletes and novices, as well as the potential of high-definition tDCS for precise brain region targeting to potentially enhance motor performance in athletic populations.

Musculoskeletal disorders and functional characteristics of the neck and shoulder: Comparison between office workers using a laptop or desktop computer.

Using a laptop for work is gaining rapid popularity, but there is little evidence of how it influences musculoskeletal disorders (MSDs) and functional characteristics of the neck and shoulder area. This study aimed to compare the prevalence of upper body MSDs and functional characteristics of the neck between office workers using a laptop or desktop computer. A total of 110 office workers with a mean age of 41±10 years participated. 45 office workers (73% female) used a laptop and 65 office workers (86% female) used desktop computers. The prevalence of MSDs was recorded using the Nordic Musculoskeletal Questionnaire. Active range of motion (AROM), maximal voluntary isometric contraction (MVC) force, joint position error (JPE), and pain-pressure threshold (PPT) of the neck and shoulder area were measured. Laptop users experienced significantly more MSDs in the right shoulder area on the day of participation (p < 0.001, OR = 4.47), during the previous 7 days (p < 0.01, OR = 3.74), and at 6 months (p < 0.01, OR = 3.57). Laptop users also experienced significantly more MSDs in the left shoulder during the previous 7 days (p < 0.05, OR = 2.44). There were no statistically significant differences in any of the functional characteristics of the neck and shoulder area between the groups. Using the laptop computer for office work may pose a higher risk of developing MSDs in the right shoulder area, but might not have long-term effects on the functional characteristics of the neck and shoulder area.

Unilaterally Induced Quadriceps Fatigue during Sustained Submaximal Isometric Exercise Does Not Alter Contralateral Leg Extensor Performance.

This study investigated the effects of fatiguing unilateral exercise on the ipsilateral, exercised, and contralateral, non-exercised limb's post-exercise performance in males and females. Ten males and ten females performed a fatiguing, unilateral isometric leg extension at 50% maximal voluntary isometric contraction (MVIC) force. Prior to and immediately after the fatiguing tasks, MVICs were performed for the exercised and non-exercised limb, with surface electromyographic (sEMG) and mechanomyography (sMMG) amplitude (AMP) and mean power frequency (MPF) recorded from each limb's vastus lateralis. There were no fatigue-induced, sex-dependent, differences in time to task failure (p = 0.265) or ipsilateral performance fatigability (p = 0.437). However, there was a limb by time interaction (p < 0.001) which indicated decreases in MVIC force of the ipsilateral, exercised (p < 0.001), but not the contralateral, non-exercised limb (p = 0.962). There were no sex-dependent, fatigue-induced differences in neurophysiological outcomes between the limbs (p > 0.05), but there was a fatigue-induced difference in sEMG MPF (p = 0.005). To summarize, there were no differences in fatigability between males and females. Moreover, there was insufficient evidence to support the presence of a general crossover effect following submaximal unilateral isometric exercise. However, independent of sex, the neurophysiological outcomes suggested that competing inputs from the nervous system may influence the performance of both limbs following unilateral fatigue.

Sustainability and perceptual responses during handgrip holds to failure at two fatigue thresholds.

Critical force (CF) provides an estimate of the asymptote of the force-duration curve and the physical working capacity at the rating of perceived exertion (PWCRPE) estimates the highest force that can be sustained without an increase in perceived exertion. Handgrip-related musculoskeletal disorders and injuries derived from sustained or repetitive motion-induced muscle fatigue are prevalent in the industrial workforce. Thus, it is important to understand the physiological mechanisms underlying performance during handgrip specific tasks to describe individual work capacities. This study examined prolonged, isometric, handgrip exercises by comparing the relative force levels, sustainability, and perceptual responses at two fatigue thresholds, CF and PWCRPE. Ten women (26.5 ± 3.5years) performed submaximal, isometric handgrip holds to failure (HTF) with the dominant hand at four, randomly ordered percentages (30, 40, 50, and 60%) of maximal voluntary isometric contraction (MVIC) force to determine CF and PWCRPE. Isometric handgrip HTF were performed at CF and PWCRPE. Time to task failure and RPE responses were recorded. There were no differences in the relative forces (p = 0.381) or sustainability (p = 0.390) between CF (18.9 ± 2.5% MVIC; 10.1 ± 2.7min) and PWCRPE (19.5 ± 7.9% MVIC; 11.6 ± 8.4min), and the RPE increased throughout both holds at CF and PWCRPE. It is possible that complex physio-psychological factors may have contributed to the fatigue-induced task failure. CF and PWCRPE may overestimate the highest force output that can be maintained for an extended period of time without fatigue or perceptions of fatigue for isometric handgrip holds.

Predicting muscle fatigue during dynamic contractions using wavelet analysis of surface electromyography signal

Muscle fatigue is defined as a reduction in the capability of muscle to exert force or power. Although surface electromyography (sEMG) signals during exercise have been used to assess muscle fatigue, analyzing the sEMG signal during dynamic contractions is difficult because of the many signal distorting factors such as electrode movements, and variations in muscle tissue conductivity. Besides the non-deterministic and non-stationary nature of sEMG in dynamic contractions, no fatigue indicator is available to predict the ability of a muscle to apply force based on the sEMG signal properties.In this study, we designed and manufactured a novel wearable sensor system with both sEMG electrodes and motion tracking sensors to monitor the dynamic muscle movements of human subjects. We detected the state of muscle fatigue using a new wavelet analysis method to predict the maximum isometric force the subject can apply during dynamic contraction.Our method of signal processing consists of four main steps. 1- Segmenting sEMG signals using motion tracking signals. 2- Determine the most suitable mother wavelet for discrete wavelet transformation (DWT) based on cross-correlation between wavelets and signals. 3- Deoinsing the sEMG using the DWT method. 4- Calculation of normalized energy in different decomposition levels to predict maximal voluntary isometric contraction force as an indicator of muscle fatigue.The monitoring system was tested on healthy adults doing biceps curl exercises, and the results of the wavelet decomposition method were compared to well-known muscle fatigue indices in the literature.

Quadriceps Function and Athletic Performance in Highly Trained Female Athletes.

Quadriceps strength is considered a key contributor to performance in various athletic tasks. Yet, past research has reported conflicting results based on population, with little data available in highly trained female athletes. Cross-sectional. To examine how athletic performance relates to quadriceps strength and neural function, we measured the quadriceps maximum voluntary isometric contraction force (MVIC) and rate of force development over 0 to 50ms (rate of force development [RFD]0-50ms), and various performance measures in 34 highly trained female athletes. Stepwise multiple regression analysis revealed that the quadriceps variables explained 16 of 21 performance variables (R2 = .08-.36, P ≤ .10). Squat performance related to RFD0-50ms alone (R2 = .17-.20, P < .05; βRFD = 0.41 to 0.45, P < .05) but only MVIC explained the variance in sprinting and vertical jump performance (R2 = .08-.34, P ≤ .10; βMVIC = -0.51 to 0.58, P ≤ .10). The broad jump model included both parameters and their interaction (R2 = .20, P = .08; βRFD = 0.06, P = .76; βMVIC = -0.39, P = .03; βRFD×MVIC = -0.24, P = .10). The contribution of the quadriceps MVIC or RFD0-50ms varies in size and nature depending on the task or leg dominance. While quadriceps are significant contributors to performance, because our models leave most of the variance in performance unexplained, rehabilitation and performance professionals should refrain from interpreting peak athletic performance as a reflection of knee-extensors function in highly trained female athletes.

Feasibility and early effects of bed-cycling eccentric training: Potential clinical applications.

This study aimed to evaluate feasibility and early effects of moderate intensity bed-cycling eccentric training on healthy individuals, and establish whether this training modality could be implemented into bedridden patients'routine care. Longitudinal study with prepost exercise intervention measurements. The development of a bed-adapted eccentric ergometer allowed to conduct five training sessions during 3 weeks at increasing intensity on 11 healthy individuals. Force-speed relationship, maximal voluntary knee extension force and neural activation of subjects were evaluated before and after the programme. Five training sessions were sufficient to decrease the rate of perceived exertion whereas eccentric power output increased (+40%). After training, maximal voluntary isometric contraction force measured during knee extension had significantly improved in all subjects, with a mean increase of 17%. Maximal cycling power was also significantly higher (+7%) after the training programme. Taken together, these results show that moderate load eccentric bed cycling (i) was feasible and efficient, (ii) did not generate excessive individual perception of effort during exercise nor develop major muscular or joint pain after training and (iii) allowed early force and power gains in healthy subjects.

Knee position sense and knee flexor neuromuscular function are similarly altered after two submaximal eccentric bouts.

This study examined eccentric-induced fatigue effects on knee flexor (KF) neuromuscular function and on knee position sense. This design was repeated across two experimental sessions performed 1week apart to investigate potential repeated bout effects. Sixteen participants performed two submaximal bouts of KF unilateral eccentric contractions until reaching a 20% decrease in maximal voluntary isometric contraction force. Knee position sense was evaluated with position-matching tasks in seated and prone positions at 40° and 70° of knee flexion so that KF were either antagonistic or agonistic during the positioning movement. The twitch interpolation technique was used to assess KF neuromuscular fatigue. Perceived muscle soreness was also assessed. Measurements were performed before, immediately (POST) and 24h after (POST24) each eccentric bout. No repeated bout effect on neuromuscular function and proprioceptive parameters was observed. At POST, central and peripheral factors contributed to the force decrement as shown by significant decreases in voluntary activation level (-3.8 ± 4.8%, p < 0.01) and potentiated doublet torque at 100Hz (-10 ± 15.8%, p < 0.01). At this time point, position-matching errors significantly increased by 1.7 ± 1.9° in seated position at 40° (p < 0.01). At POST24, in presence of muscle soreness (p < 0.05), although KF neuromuscular function had recovered, position-matching errors increased by 0.6 ± 2.6° in prone position at 40° (p < 0.01). These results provide evidence that eccentric-induced position sense alterations may arise from central and/or peripheral mechanisms depending on the testing position.

Repeated Simulated Match-Induced Changes in Finger Flexor Force and Blood Acid-Base Balance in World-Class Female Judokas.

The aim of this study was to investigate the time course of maximal isometric finger flexor force and blood acid-base balance during repeated simulated matches in world-class judokas. Seven 21- to 28-year-old world-class female judokas (including Olympic and World Championship medalists) repeated four 4-minute judo combats interspersed by 15minutes of passive recovery. Maximal voluntary isometric finger flexor contraction (MVIC) force was measured in both hands after warm-up and immediately after each combat using a handgrip dynamometer. MVIC force was classified as MVIC hikite force (pulling hand) and MVIC tsurite force (lifting hand). Blood lactate concentration, pH, bicarbonate concentration, partial pressure of oxygen, and oxygen saturation were measured between 3 and 5 minutes after each match. At completion of the fourth combat, mean MVIC hikite and tsurite force decreased by 18% and 12%, respectively (g = 0.23 and 0.29, respectively; P < .05), demonstrating that force production was substantial throughout repeated matches. Blood lactate concentration increased ∼5-fold from 2.69 (1.37)mmol·L-1 after warm-up to 13.10 (2.61)mmol·L-1 after the last match (g = 4.13, P = .018). Concurrently, blood pH decreased slightly from 7.44 (0.03) to 7.26 (0.05) (g = 2.34, P = .018), that is, by only 0.18 units. The decreased blood pH was significantly correlated with a decrease in bicarbonate concentration (R2 = .94, P < .001). Finally, partial pressure of oxygen and oxygen saturation remained unchanged during the judo contest. Female world-class judokas were able to maintain a high level of grip strength in both hands and efficiently regulate blood acid-base balance during repeated simulated high-intensity matches.

Comparison between Eccentric-Only and Coupled Concentric-Eccentric Contractions for Neuromuscular Fatigue and Muscle Damage.

Eccentric contractions induce muscle damage, but less is known about the effects of preceding concentric contractions to eccentric contractions on muscle damage. We compared eccentric-only (ECC) and coupled concentric and eccentric contractions (CON-ECC) of the knee extensors for parameters of neuromuscular fatigue and muscle damage. Twenty participants (age, 19-36 yr) were randomly placed into an ECC or a CON-ECC group (n = 10 per group), without significant (P > 0.06) differences in baseline neuromuscular variables between groups. The ECC group performed six sets of eight ECC at 80% of ECC one-repetition maximum (1-RMecc), whereas the CON-ECC group performed six sets of eight alternating concentric (CON) and ECC (16 contractions per set) at 80% of CON 1-RM and 1-RMecc, respectively. Maximal voluntary isometric contraction force, rate of force development, resting twitch force, maximal M-wave (MMAX), voluntary activation, motor evoked potentials, corticospinal silent period, short interval intracortical inhibition, and muscle soreness were measured before, immediately after, and 1-3 d after exercise. No significant (P ≥ 0.09) differences between ECC and CON-ECC were observed for changes in any variables after exercise. However, maximal voluntary isometric contraction force decreased immediately after exercise (ECC: -20.7% ± 12.8%, CON-ECC: -23.6% ± 23.3%) and was still reduced 3 d after exercise (ECC: -13.6% ± 13.4%, CON-ECC: -3.3% ± 21.2%). Rate of force development at 0-30 ms reduced immediately after exercise (ECC: -38.3% ± 33.9%, CON-ECC: -30.7% ± 38.3%). Voluntary activation, resting twitch force, and motor evoked potential/MMAX decreased and corticospinal silent period increased after exercise (all P ≤ 0.03), but short interval intracortical inhibition and MMAX did not change. Muscle soreness developed (P < 0.001) similarly for both groups (peak, 38.5 ± 29.5 mm). CON-ECC did not exacerbate neuromuscular fatigue and muscle damage when compared with ECC, despite twice as many contractions performed. Thus, eccentric contractions (n = 48 in both groups) seemed to mainly mediate the neuromuscular responses observed.

Downhill running affects the late but not the early phase of the rate of force development

PurposeThis study aimed to evaluate the acute changes in the knee extensors maximum voluntary isometric contraction force (MVIC), rate of force development (RFD), and rate of EMG rise (RER) following a bout of downhill running.MethodsMVIC and RFD at 0–50, 50–100, 100–200, and 0–200 ms were determined in thirteen men (22 ± 2 yr) before and after 30 min of downhill running (speed: 10 km h−1; slope: − 20%). Vastus lateralis maximum EMG (EMGmax) and RER at 0–30, 0–50, and 0–75 ms were also recorded.ResultsMVIC, RFD0–200, and EMGmax decreased by ~ 25% [Cohen’s d = − 1.09 (95% confidence interval: − 1.88/− 0.24)], ~ 15% [d = − 0.50 (− 1.26/0.30)], and ~ 22% [d = − 0.37 (− 1.13/0.42)] (all P < 0.05), respectively. RFD100–200 was also reduced [− 25%; d = − 0.70 (− 1.47/0.11); P < 0.001]. No change was observed at 0–50 ms and 50–100 ms (P ≥ 0.05). RER values were similar at each time interval (all P > 0.05).ConclusionDownhill running impairs the muscle capacity to produce maximum force and the overall ability to rapidly develop force. No change was observed for the early phase of the RFD and the absolute RER, suggesting no alterations in the neural mechanisms underlying RFD. RFD100–200 reduction suggests that impairments in the rapid force-generating capacity are located within the skeletal muscle, likely due to a reduction in muscle–tendon stiffness and/or impairments in the muscle contractile apparatus. These findings may help explain evidence of neuromuscular alterations in trail runners and following prolonged duration races wherein cumulative eccentric loading is high.

Changes in biceps brachii muscle hardness assessed by a push-in meter and strain elastography after eccentric versus concentric contractions

Changes in biceps brachii muscle hardness assessed by a push-in meter (PM) and strain elastography (SE) were compared between eccentric (ECC) and concentric contractions (CON) of the elbow flexors to test the hypothesis that muscle hardness would increase greater after ECC. Ten men performed 5 sets of 10 ECC with their non-dominant arms and 5 sets of 10 CON with their dominant arms using a dumbbell corresponding to 50% of maximum voluntary isometric contraction (MVIC) force at 90º elbow flexion. Before and 1–4 days after the exercise, MVIC force, elbow joint angles, upper-arm circumference, and muscle soreness as muscle damage makers, and biceps brachii muscle hardness at maximally extended elbow joint by PM and SE were measured. Changes in these measures over time were compared between ECC and CON. All muscle damage markers showed greater changes after ECC than CON (p < 0.001). Muscle hardness assessed by PM and SE increased (p < 0.05) and peaked at 4 days post-ECC with 154.4 ± 90.0% (PM) and 156.2 ± 64.2% (SE) increases from the baseline, but did not change significantly after CON. The changes in muscle hardness post-ECC were correlated between PM and SE (r = 0.752, p < 0.001). A correlation (p < 0.001) between the normalized changes in resting elbow joint angle and changes in muscle hardness assessed by PM (r = − 0.772) or SE (r = − 0.745) was also found. These results supported the hypothesis and suggest that the increases in muscle hardness after ECC were associated with muscle damage (increased muscle stiffness), and PM and SE detected muscle hardness changes similarly.

Mitochondria-targeted antioxidant supplementation does not affect muscle soreness or recovery of maximal voluntary isometric contraction force following muscle-damaging exercise in untrained men: a randomized clinical trial.

Unaccustomed exercise causes muscle damage resulting in loss of muscle function, which may be attributable to exercise-induced increases in skeletal muscle reactive oxygen species. This study examined the effect of mitochondria-targeted antioxidant supplementation on recovery of muscle function following exercise. Thirty-two untrained men received MitoQ (20mg/day) or a placebo for 14 days before performing 300 maximal eccentric contractions of the knee extensor muscles of 1 leg. Muscle function was assessed using isokinetic dynamometry before, immediately after, and 24, 48, 72, and 168 hours after exercise. Muscle soreness was assessed using a visual analogue scale 24, 48, 72, and 168 hours after exercise. Blood samples were collected before, immediately after, and 2, 24, 48, 72, and 168 hours after exercise and urine samples were collected before and during the 48 hours after exercise. The reduction in maximal voluntary isometric contraction force and peak concentric torque following exercise was unaffected by MitoQ while recovery of peak eccentric torque was delayed in the MitoQ group. Exercise-induced increases in urine F2-isoprostanes were unaffected by MitoQ. MitoQ augmented exercise-induced increases in plasma creatine kinase levels, while plasma IL-6 was similar between groups. Muscle soreness was not affected by MitoQ. These results indicate that MitoQ does not attenuate post-exercise muscle soreness and may delay recovery of muscle function following eccentric exercise. Trial registration number: ACTRN12620001089921. Novelty: Post-exercise recovery of maximal voluntary isometric contraction force and peak concentric torque were unaffected by MitoQ. MitoQ delayed post-exercise recovery of peak eccentric torque. Post-exercise muscle soreness was unaffected by MitoQ.

Age-related increase in muscle stiffness is muscle length dependent and associated with muscle force in senior females

BackgroundIn aging, muscle stiffness is considered as one of the factors associated with the reduction of force generation capability. There have been inconsistent findings on age-related alteration in the passive stiffness of quadriceps muscle in the female adults. Thus, the aim of this study was to determine the effect of aging on the shear moduli of the superficial muscle heads of the quadriceps and to explore its relationship with knee extension force.MethodsPassive shear moduli of the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) were measured at rest using shear wave elastography in 20 young and 20 senior female adults. Measurements were repeated at four knee joint positions, that is, 30°, 60°, 90°, and 105° of knee flexion. Maximal isometric voluntary knee extension force was assessed at 30°, 60°, and 90° of knee flexion.ResultsAs per our findings, senior adults were determined to have significantly higher passive muscle shear moduli in the RF (by 34% – 68%; all p < 0.05) and the VL muscle heads (by 13%–16%, all p < 0.05) at and beyond 60° of knee flexion. Age-related increase in the VM was evident at 105° knee flexion (by11%, p = 0.020). The RF shear modulus was negatively correlated to the maximal isometric voluntary contraction force measured at 60° (r = − 0.485, p = 0.030) in senior adults.ConclusionsSenior female adults had greater passive stiffness at the superficial muscle heads of the quadriceps muscles when measured at long muscle length. Among the senior female adults, the passive stiffness of RF has been determined to have a negative association with the knee extensor force only at 60° knee flexion. No significant association was noted for other angles and muscles.

Recovery From Eccentric Squat Exercise in Resistance-Trained Young and Master Athletes With Similar Maximum Strength: Combining Cold Water Immersion and Compression.

The aim of this study was to investigate whether recovery from eccentric squat exercise varies depending on age and to assess whether the use of a mixed-method recovery (MMR) consisting of cold water immersion and compression tights benefits recovery. Sixteen healthy and resistance-trained young (age, 22.1±2.1years; N=8) and master male athletes (age, 52.4±3.5years; N=8), who had a similar half squat 1-repetition maximum relative to body weight, completed two identical squat exercise training sessions, separated by a 2-week washout period. Training sessions were followed by either MMR or passive recovery (PR). Internal training loads [heart rate and blood lactate concentration (BLa)] were recorded during and after squat sessions. Furthermore, maximal voluntary isometric contraction (MVIC) force, countermovement jump (CMJ) height, resting twitch force of the knee extensors, serum concentration of creatine kinase (CK), muscle soreness (MS), and perceived physical performance capability (PPC) were determined before and after training as well as after 24, 48, and 72h of recovery. A three-way mixed ANOVA revealed a significant time effect of the squat protocol on markers of fatigue and recovery (p<0.05; decreased MVIC, CMJ, twitch force, and PPC; increased CK and MS). Age-related differences were found for BLa, MS, and PPC (higher post-exercise fatigue in younger athletes). A significant two-way interaction between recovery strategy and time of measurement was found for MS and PPC (p<0.05; faster recovery after MMR). In three participants (two young and one master athlete), the individual results revealed a consistently positive response to MMR. In conclusion, master athletes neither reach higher fatigue levels nor recover more slowly than the younger athletes. Furthermore, the results indicate that MMR after resistance exercise does not contribute to a faster recovery of physical performance, neuromuscular function, or muscle damage, but promotes recovery of perceptual measures regardless of age.

Skeletal muscle properties and vascular function do not differ between healthy, young vegan and omnivorous men

ABSTRACT A vegan diet is associated with reduced cardiovascular morbidity and mortality, but protein deficiencies may be detrimental to skeletal muscle structure and function. The aim of this study was to compare the vascular and skeletal muscle properties between young, healthy, recreationally active habitual vegan (VEG) and omnivorous (OMN) men. Sixteen OMN and nine VEG underwent ultrasound scans to determine brachial artery flow-mediated dilation (FMD) and carotid artery intima-media thickness (cIMT) and vastus lateralis (VL) muscle thickness and fascicle pennation angle. Knee extension maximal voluntary isometric contraction (MVIC) force was assessed on an isokinetic dynamometer, and O2max on a cycle ergometer and online gas analysis system. A three-day food diary determined habitual dietary behaviour. Bayesian analyses of independent groups provided “moderate” to “very strong” evidence for lower consumption of absolute (63±21 g/d vs. 98 ± 30 g/d; Bayes Factor (BF01) = 0.140) and relative (0.86 ± 0.29 g/kg/d vs.1.36 ± 0.52 g/kg/d; BF01 = 0.259) protein, absolute saturated fat (15.2 ± 7.9 g vs. 30.3 ± 11.8 g; BF01 = 0.089) and cholesterol (5.0 ± 6.0 mg vs. 337.9 ± 232.6 mg; BF01 = 0.019) in VEG compared to OMN, respectively. Further, there was “anecdotal” evidence to support no differences in FMD (3.37 ± 3.31% vs. 4.58 ± 5.82%; BF01 = 2.591), cIMT (0.51 ± 0.07 mm vs. 0.49 ± 0.04 mm; BF01 = 2.510), VL thickness (26.1 ± 3.7 mm vs. 27.8 ± 6.4 mm; BF01 = 2.726), fascicle pennation angle (16.6 ± 4.7° vs. 17.7 ± 3.7°; BF01 = 2.844), MVIC (627 ± 182 N vs. 551 ± 102 N; BF01 = 1.656) or O2max (40.8 ± 9.8 ml/kg/min vs. 35.8 ± 5.2 ml/kg/min; BF01 = 1.218) between VEG and OMN, respectively. Despite marked differences in habitual nutrient intake, healthy, young vegan and omnivorous men did not differ regarding vascular and skeletal muscle structure and function, or cardiovascular fitness.