Gender difference in the relationship of performance in the handgrip and standing long jump tests to lean limb volume in young adults

Groups of young, adult males and females performed the handgrip and standing long jump tests. Their total forearm and leg volumes were calculated from a series of circumference and length measurements, and the lean volumes (bone + muscle) calculated by taking the skinfold thickness into consideration. In the handgrip, the mean female performance was 298 N compared with 496 N for the males. In the standing long jump, mean performance expressed as distance x body mass was 87.3 kg.m for females compared with 137.7 kg.m for males. These superior performances of males could simply reflect their greater muscle mass, as the mean lean volumes of female and male limbs respectively were 0.54 l and 0.89 l for forearms, and 11.82 l and 14.82 l for the two legs. However, when the performances of males and females were grouped by lean limb volume, it was found that while in both tests there were linear relationships, males and females did not share a common line. In both tests the male relationship was at a higher level than the female; therefore, for a given lean volume, the male performance was significantly superior to that of the female. The gender difference found in this study has not been seen in other studies in which the performance of skeletal muscle has been related to the cross-sectional area of the active muscles and the possible reasons for the differences are considered.     

Acute Hypoxemia Does Not Increase the Oxidative Stress in Resting and Contracting Muscle in Humans

In healthy humans sustaining static handgrip at 60% of maximal voluntary contraction (MVC) until exhaustion, we measured the venous blood concentration of reduced ascorbic acid (RAA) and thiobarbituric acid reactive substances (TBARS), respectively, used as markers of the post-exercise oxidative stress and lipid peroxidation. Measurements were conducted in normoxemia, then during a 30-min period of hypoxemia (PaO 2 =56 mmHg) produced by inhalation of an hypoxic gas mixture. Compared to normoxemia, hypoxemia did not significantly modify the resting concentrations of TBARS and RAA, and did not affect the consumption of ascorbic acid after 60% MVC but suppressed the post-exercise TBARS increase. We conclude that acute hypoxemia does not modify the production of oxygen free radicals after strenuous static efforts and even seems to attenuate the lipid peroxidation.     

Local cryostimulation acutely preserves maximum isometric handgrip strength following fatigue in young women

Several types of cryostimulation have been recently proposed to rapidly lower skin temperature therefore gaining a possible neuro/muscular recovery after strenuous exercise or, more generally, in sports. Local cryostimulation may be a viable and relatively portable tool to obtain physiological benefits in previously-efforted muscular districts. However, cohesive and standardized cryo-exposure protocols are lacking as well as the righteous procedure to efficaciously combine duration, treatments and temperature in relation to desirable effects on muscular strength. In this randomized-controlled study, fifty young women were tested for maximum isometric handgrip strength, before and after exhausting contractions.Following the fatiguing protocol, the intervention group (cryo, n = 25, 24.7 ± 2.5 years, BMI 21.7 ± 1.8 kg/m²) underwent a 6-min local cryostimulation (−160 °C) on the extensor-flexor muscles of the dominant arm, while control-matched peers sat rested in a thermo-neutral room (22 ± 0.5 °C). Handgrip tests were repeated at baseline (T0), after cryostimulation (T1), and 15 min after T1 (T2). Throughout the protocol, the AUC of the strength performance was significantly higher in the cryo- compared to control group (P = 0.006). In particular, following fatigue and cryostimulation, the cryo group preserved higher strength at T1 with respect to controls (26.8 ± 2.8 vs 23.9 ± 2.8 kg, Bonferroni's post-hoc, P < 0.01). Likewise, ventral and dorsal temperature, recorded with a thermal camera, were lower in cryo- than control group (P < 0.0001).In conclusion, a brief session of local cryostimulation may acutely preserve maximal isometric force in young women following a fatiguing protocol. These findings may have implications in orchestrating strategies of district muscular recovery.     

Quantitative assessment of upper limb muscle fatigue depending on the conditions of repetitive task load

The aim of this study was to discriminate fatigue of upper limb muscles depending on the external load, through the development and analysis of a muscle fatigue index. Muscle fatigue is expressed by a fatigue index based on an amplitude parameter (calculated in the time domain) and a fatigue index based on a frequency parameter (a parameter calculated in the frequency domain). The fatigue index involves a regression function that describes changes in the EMG signal parameter, time elapsing before muscle fatigue and the probability of specific trends in changes in EMG parameters for the population under study.

The experimental study covered a group of 10 young men. During the study, they exerted force at a specific level and for a specific time in 12 load variants. During the study, EMG signals from four muscles of the upper limb were recorded (trapezius pars descendents, biceps brachii caput breve, extensor carpi radialis brevis, flexor carpi ulnaris). For each variant and for each examined muscles, the value of the fatigue index was calculated. Values of that index quantitatively expressed fatigue of a specific muscle in a specific load variant.

A statistical analysis indicated variation in the fatigue of the biceps brachii caput breve, extensor carpi radialis brevis, and flexor carpi ulnaris muscles depending on the external load (load variant) according to the task performed with the upper limb.

The study demonstrated usefulness of the fatigue index in expressing quantitatively muscle fatigue and in discriminating muscle fatigue depending on the external load.     

Acute hypoxemia does not increase the oxidative stress in resting and contracting muscle in humans

In healthy humans sustaining static handgrip at 60% of maximal voluntary contraction (MVC) until exhaustion, we measured the venous blood concentration of reduced ascorbic acid (RAA) and thiobarbituric acid reactive substances (TBARS), respectively, used as markers of the post-exercise oxidative stress and lipid peroxidation. Measurements were conducted in normoxemia, then during a 30-min period of hypoxemia (PaO 2 =56 mmHg) produced by inhalation of an hypoxic gas mixture. Compared to normoxemia, hypoxemia did not significantly modify the resting concentrations of TBARS and RAA, and did not affect the consumption of ascorbic acid after 60% MVC but suppressed the post-exercise TBARS increase. We conclude that acute hypoxemia does not modify the production of oxygen free radicals after strenuous static efforts and even seems to attenuate the lipid peroxidation.     

Cardiovascular responses to light isometric and aerobic exercise in 21- and 59-year-old males

The effects of aging on the cardiovascular response to continuous light isometric and aerobic exercise remains to be determined. Thus, the purpose of this study was to compare the cardiovascular response of young and older males during light handgrip and cycle ergometry exercise. Blood pressure, heart rate, rate pressure product, as well as pre-ejection period (derived from impedance cardiography) were obtained for 15 young [mean (SE) age: 21 (0.7) years] and 15 older males [59 (0.8) years] during and after light handgrip exercise and cycle ergometry. The parasympathetic influence on the heart was also assessed through a time-series analysis of heart period variability (HPVts). Both during and when recovering from the handgrip exercise and cycle ergometry, the older subjects exhibited a significantly higher absolute systolic and diastolic blood pressure, and rate pressure product, and a lower HRVts than the young subjects. Relative to baseline, the change in pre-ejection period was lower for the young subjects during the handgrip and cycle ergometry, tasks. These results indicate that although the sympathetic influence on both the myocardium and the vasculature was less pronounced in the older males, the aging cardiovasculature was under greater hemodynamic stress both during rest and during exposure to light isometric and aerobic challenge.     

Cardiac responses to maximal anisotonic isometric contractions during handgrip and leg extension

A group of 14-healthy men performed anisotonic isometric contractions (AIC), for 60 s, at an intensity of 100% maximal voluntary contraction force (MVC) during handgrip (HG) and leg extension (LE). Heart rate (f _c), stroke volume index (SVI) and cardiac output index (Q_cI) were measured during the last 10 s of both AIC by an impedance reography method. Force (F) exerted by the subjects was recorded continuously and reported as a relative force (F _r) (% MVC). The F generated during MVC was greater for LE than for HG (502.I N compared to 374.6 N, P < 0.001). The rate of decrease in F _r was significantly slower for LE than HG for the first 25 s of the exercise (phase 1 of AIC). The F _r developed by the subjects at the end of AIC was 40% MVC for both LE and HG. The increase in f _c was greater for LE (63 beats · min^–1) than for HG (52 beats · min^–1), P < 0.01. The SVI decreased significantly from the resting level by 17.0 ml · m^–2 and by 18.2 ml · m^–2 for LE and HG, respectively. The Q_cI increased insignificantly for HG by 0.091 · min^–1 · m^–2 andsignificantly forLE by 0.561 · min^–1 · m^–2 (P < 0.001). It was concluded that although both AIC caused a significant decrease in SVI, greater increases in f _c and Q_c were observed for LE than for HG. The greater f _c and Q_c reported during LE was probably related to the greater relative force exerted by LE during phase 1 of AIC. It seems, therefore that central command might have dominated for phase 1 of AIC but that the muscle reflex also contributed significantly to the control of the cardiac response to the high intensity AIC.     

The relationship of lean limb volume to performance in the handgrip and standing long jump tests in boys and girls, aged 11.6–13.2 years

Twenty-three girls and 19 boys performed the handgrip and standing long jump (SLJ) tests. Their total forearm and leg volumes were calculated from circumference and length measurements and the lean volumes (bone + muscle) were calculated by making allowance for skinfold thickness. Although the boys were older than the girls (12.8 and 12.4 years), there was no significant difference in their heights or body masses. The absolute performances of the boys were superior to those of the girls in both tests (handgrip 234 and 205 N and SLJ 1.53 and 1.34 m), but when jumping performance was expressed as distance x body mass, there was no significant difference. In both tests, performance in terms of unit lean limb volume showed no significant gender difference. When performance was related to lean limb volume, both boys and girls showed a linear relationship in the two tests, with no significant difference between them. This absence of a gender difference contrasts with the results of a previous study on young adults and comparison shows that the relationships between lean limb volume and performance in the two tests for both boys and girls lie just below those of the young, adult females. The difference between the girls and the young adult females was just significant in the handgrip (p less than 0.05), but not significant in the SLJ (p greater than 0.25), whereas the differences between the boys and young adult males were significant (p less than 0.01) in both tests. Thus it would appear that a gender difference in the performance of skeletal muscle develops during adolescence and possible contributory factors are discussed.     

Cardiovascular response to static handgrip in trained and untrained men

The influence of aerobic capacity on the cardiovascular response to handgrip exercise, in relation to the muscle mass involved in the effort, was tested in 8 trained men (T) and 17 untrained men (U). The subjects performed handgrip exercises with the right-hand (RH), left-hand (LH) and both hands simultaneously (RLH) at an intensity of 25% of maximal voluntary contraction force. Maximal aerobic capacity was 4.3 l.min-1 in T and 3.21 l.min-1 in U (P less than 0.01). The endurance time for handgrip was longer in T than in U by 29% (P less than 0.05) for RH, 38% (P less than 0.001) for LH and 24% (P less than 0.001) for RLH. Heart rate (fc) was significantly lower in T than in U before handgrip exercise, and showed smaller increases (P less than 0.01) at the point of exhaustion: 89 vs 106 beats.min-1 for RH, 93 vs 100 beats.min-1 for LH and 92 vs 108 beats.min-1 for RLH. Stroke volume (SV) at rest was greater in T than in U and decreased significantly (P less than 0.05) during handgrip exercise in both groups of subjects. At the point of exhaustion SV was still greater in T than in U: 75 vs 57 ml for RH, 76 vs 54 ml for LH and 76 vs 56 ml for RLH. During the last seconds of handgrip exercise, the left ventricular ejection time was longer in T than in U. Increases in cardiac output (Qc) and systolic blood pressure did not differ substantially between T and U, nor between the handgrip exercise tests.(ABSTRACT TRUNCATED AT 250 WORDS)     

RIGHT- AND LEFT-BRAIN HEMISPHERE. RHYTHM IN REACTION TIME TO LIGHT SIGNALS IS TASK-LOAD-DEPENDENT: AGE,GENDER, AND HANDGRIP STRENGTH RHYTHM COMPARISONS

In healthy mature subjects simple reaction time (SRT) to a single light signal (an easy task) is associated with a prominent rhythm with τ=24 h of dominant (DH) as well as nondominant (NDH) hand performance, while three-choice reaction time (CRT), a complex task, is associated with τ=24 h of the DH but τ<24 h of the NDH. The aims of the study were to assess the influence of age and gender on the difference in τ of the NDH and DH, as it relates to the corresponding cortical hemisphere of the brain, in comparison to the rhythm in handgrip strength. Healthy subjects, 9 (5 M and 4 F) adolescents 10–16 yr of age and 15 (8 M and 7 F) adults 18–67 yr of age, active between 08:00±1 h and 23:00±1:30 h and free of alcohol, tobacco, and drug consumption volunteered. Data were gathered longitudinally at home and work 4–7 times daily for 11–20 d. At each test time the following variables were assessed: grip strength of both hands (Dynamometer: Colin–Gentile, Paris, France); single reaction time to a yellow signal (SRT); and CRT to randomized yellow, red, or green signal series with varying instruction from test to test (Psycholog-24: Biophyderm, France). Rhythms in the performance in SRT, CRT, and handgrip strength of both DH and NDH were explored. The sleep–wake rhythm was assessed by sleep-logs, and in a subset of 14 subjects it was also assessed by wrist actigraphy (Mini-Motionlogger: AMI, Ardsley NY). Exploration of the prominent period τ of time series was achieved by a special power spectra analysis for unequally spaced data. Cosinor analysis was used to quantify the rhythm amplitude A and rhythm-adjusted mean M of the power spectral analysis determined trial τ. A 24h sleep–wake rhythm was detected in almost all cases. In adults, a prominent τ of 24 h characterized the performance of the easy task by both the DH and NDH. In adults a prominent τ of 24 h was also detected in the complex CRT task performed by the DH, but for the NDH the τ was <24 h. This phenomenon was not gender-related but was age-related since it was seldom observed in adolescent subjects. Hand-side differences in the grip strength rhythms in the same individuals were detected, the τ being ultradian rather than circadian in adolescent subjects while in mature subjects the τ frequently differed from that of the rhythm in CRT. These findings further support the hypothesis that functional biological clocks exist in both the left and right hemispheres of the human cortex.