Strength and power changes of the human plantar flexors and knee extensors in response to resistance training in old age

Aim: The aim of the present study was to assess and compare the improvements of muscle strength and power induced by a 16-week resistive programme in a population of 16 older men aged 65-81 years. Methods: Training was performed three times per week at an intensity of 80% of one repetition maximum (1RM) and consisted of both calf raise and leg press exercises. Before-, during- and after-training, maximum isometric and isokinetic torques, maximum power, 1RM, muscle cross-sectional area (CSA) and electromyographic activity (EMG) of the plantar flexors (PF) and knee extensors (KE) were examined. Results: For the KE and PF, respectively, training resulted in a 29.9 ± 4.4% (mean ± SE) and 21.6 ±…

Short-term changes in the series elastic component after an acute eccentric exercise of the elbow flexors

We have studied the effect of a unique eccentric exercise session on the series elastic component (SEC) properties of human elbow flexors. Ten active females performed five sets of ten maximal eccentric contractions on an isokinetic ergometer. Maximal isometric (MVC) torque, and the corresponding myoelectrical activity (RMS) of the biceps brachii and the triceps brachii muscles were recorded before, immediately after, 48 h after, and 1 week after the exercise session. SEC compliance was also measured, using the in situ quick-release technique. Maximal eccentric torque declined significantly among the five sets of the exercise session (P < 0.01). The exercise session induced a significant de…

Viscosity of the elbow flexor muscles during maximal eccentric and concentric actions.

The aim of the present study was to estimate the damping coefficient (B factor) of the elbow flexor muscles during both eccentric and concentric muscle actions. We used a muscle model consisting of a viscous damper associated in parallel with a contractile component, both in series with an elastic component. The viscous damper allowed the concentric loss and the eccentric gain of force to be modelled. Eight volunteer subjects performed maximal eccentric and concentric elbow movements on an isokinetic dynamometer at angular velocities of 0.52, 1.04 and 2.09 rad*s(-1). Torques at an elbow joint angle of 90 degrees were recorded. Electromyogram (EMG) signals from the belly of the right elbow f…

Effets de la pratique de l'escalade sur la contractilité musculaire

Resume Les caracteristiques biomecaniques des flechisseurs du coude et du poignet de sujets grimpeurs sont comparees a celles de sujets non pratiquants. Les mesures sont realisees a l'aide d'un ergometre isocinetique sur une plage de vitesses angulaires s'etalant de 120°·s −1 en excentrique a 360°·s −1 en concentrique. Les relations couple maximum/vitesse angulaire montrent que les sujets grimpeurs developpent un couple maximum plus eleve que les sujets temoins sur une plage de vitesse angulaire allant de 60°·s −1 en excentrique a 120°·s −1 en concentrique. Les differences entre les valeurs de couple maximum excentrique et concentrique sont identiques pour les deux groupes de sujets. Lors d…

Effect of electrical stimulation training on the contractile characteristics of the triceps surae muscle.

This study aimed to assess the effects of training using electrical stimulation (ES) on the contractile characteristics of the triceps surae muscle. A selection of 12 subjects was divided into two groups (6 control, 6 experimental). The ES sessions were carried out using a stimulator. Flexible elastomer electrodes were used. The current used discharged pulses lasting 200 microseconds at 70 Hz. Contraction time was 5 s and rest time 15 s. The session lasted 10 min for each muscle. Training sessions were three times a week for 4 weeks. Biomechanical tests were performed using an isokinetic ergometer. Subjects performed plantar flexions of the ankle over a concentric range of movement at diffe…

Neuromuscular electrical stimulation leads to physiological gains enhancing postural balance in the pre‐frail elderly

International audience; Physiological aging leads to a progressive weakening of muscles and tendons, thereby disturbing the ability to control postural balance and consequently increasing exposure to the risks of falls. Here, we introduce a simple and easy-to-use neuromuscular electrical stimulation (NMES) training paradigm designed to alleviate the postural control deficit in the elderly, the first hallmarks of which present as functional impairment. Nine pre-frail older women living in a long-term care facility performed 4 weeks of NMES training on their plantarflexor muscles, and seven nontrained, non-frail older women living at home participated in this study as controls. Participants w…

Effect of angular velocity on soleus and medial gastrocnemius H-reflex during maximal concentric and eccentric muscle contraction.

At rest, the H-reflex is lower during lengthening than shortening actions. During passive lengthening, both soleus (SOL) and medial gastrocnemius (MG) H-reflex amplitudes decrease with increasing angular velocity. This study was designed to investigate whether H-reflex amplitude is affected by angular velocity during concentric and eccentric maximal voluntary contraction (MVC). Experiments were performed on nine healthy men. At a constant angular velocity of 60 degrees /s and 20 degrees /s, maximal H-reflex and M-wave potentials were evoked at rest (i.e., H(max) and M(max), respectively) and during concentric and eccentric MVC (i.e., H(sup) and M(sup), respectively). Regardless of the muscl…

The Effects of a Prolonged Running Exercise on Strength Characteristics

The aim of this study was to examine concentric, isometric, and eccentric strength reductions in the quadriceps muscle following a prolonged running exercise. Before and after a 2 h run (28.4+/-1.4 km) peak torque (PT) of the knee extensors at angular velocities of -120, -90, -60, 0, 60, 120, 180, 240 degrees x s(-1) using an isokinetic dynamometer, electromyographic (EMG) activity of the vastus lateralis (VL) and vastus medialis (VM) muscles and height of a counter movement jump were recorded in twelve well-trained triathletes. Counter movement jump performances decreased by 10% and PT values were all significantly lower (p < 0.01) at each angular velocity following the run. The torque los…

EMG activity and voluntary activation during knee-extensor concentric torque generation

This study was designed to re-examine and compare the neural drive of the knee extensors during isokinetic concentric muscular actions by means of the twitch interpolation technique (activation level, AL) and surface electromyographic (EMG) recordings (root mean square, RMS). Torque, AL and RMS amplitudes of three knee extensors and one knee flexor were measured in nine subjects during maximal and sub-maximal voluntary contractions, performed under concentric (60 degrees.s(-1) and 120 degrees.s(-1); Con60 and Con120, respectively) and isometric (Iso) conditions. Mean (SD) maximal voluntary torque was significantly lower ( P0.01) during concentric contractions [Con60: 208.6 (26.8) Nm and Con…

Specific effects of eccentric training on muscular fatigability.

This study was designed to test the hypothesis that an eccentric training period induces a reduction of neuromuscular fatigability following an eccentric exercise. Before (Pre-T) and after (Post-T) a 7-wks sub-maximal eccentric training, ten active males performed a fatiguing exercise consisting of five sets of ten maximal eccentric elbow flexions. Before (Pre-T-1 and Post-T-1) and after (Pre-T-2 and Post-T-2) each fatiguing exercise, the voluntary torque and its associated agonistic electromyographic activity (RMS), assessed at four angular velocities (-60 degrees x s (-1); 0 degrees x s (-1); 60 degrees x s (-1); 240 degrees x s (-1)) were measured. The isometric voluntary activation leve…

Behavior of fascicles and the myotendinous junction of human medial gastrocnemius following eccentric strength training

This study is the first in which measurements of thickness, fascicle angle and length, and tendon elongation were combined to examine the impact of eccentric strength training on both muscle architecture and tendinous structures. Eighteen healthy male subjects were divided into an eccentric strength training group (n = 10) and a control group (n = 8). The training program consisted of 18 sessions of eccentric exercises over a 7-week period. All subjects were tested at baseline and after the last training session. Using ultrasound imaging, the fascicle angle and length and thickness of the medial gastrocnemius (MG) were analyzed at rest (i.e., theta(p), Fl(p), and t(p), respectively), at 50%…

Effets d’une séance d’exercices excentriques sur la récupération à court terme de la contractilité musculaire

Les effets a court terme de 5 series de 10 contractions maximales excentriques des flechisseurs du coude, realisees sur un ergometre isocinetique, sont etudies. Le moment maximal excentrique, isometrique, concentrique, l’activite myoelectrique des biceps et triceps brachii, le niveau d’activation volontaire, l’amplitude de la reponse M, l’amplitude de la secousse, les vitesses maximales de contraction et de relaxation sont mesures avant (Temoin), 2 minutes apres (Post), 24 heures (Post24h) et 48 heures (Post48h) apres la seance d’exercice.Le moment est significativement diminue de Temoin a Post48h, quel que soit le mode de contraction, excepte le moment concentrique mesure a 240°.s-l , qui …

Isokinetic strength and anaerobic power of elite, subelite and amateur French soccer players.

Information about the influence of different practice levels on physical characteristics of a large number of soccer players is lacking. Therefore we assessed muscular strength and anaerobic power of elite, subelite and amateur soccer players to clarify what parameters distinguish the top players from the less successful. We tested 95 soccer players from the French first division (elite), second division (subelite), and amateurs and determined the isokinetic strength of the knee extensor and flexor muscles at angular velocities from -120 degrees x s(-1) to 300 degrees x s(-1). Vertical jump, 10 m sprint, 30 m sprint and maximum ball speed during shooting were also measured. The elite player…

Changes in mechanical properties of human plantar flexor muscles in ageing

Changes in contractile and elastic properties of human plantar flexor muscles in ageing, were investigated in 12 young (19-24 years, YG) and 11 old (61-74 year, OG) men. Maximal isometric and concentric voluntary torques, at several angular velocities, were measured to construct torque-angular velocity relationship. This led to the calculation of an index of maximal shorting velocity (VImax) at low torque. Two methods were then used to calculate musculotendinous (MT, quick-release movements) and musculoarticular (MA, sinusoidal perturbations) stiffness. In both cases, stiffness was linearly related to torque, leading to the calculation of a stiffness index (SI) as the slope of the stiffness…

Isokinetic elbow flexion and coactivation following eccentric training.

The influence of an eccentric training on torque/angular velocity relationships and coactivation level during maximal voluntary isokinetic elbow flexion was examined. Seventeen subjects divided into two groups (Eccentric Group EG, n = 9 Control Group CG, n = 8) performed on an isokinetic dynamometer, before and after training, maximal isokinetic elbow flexions at eight angular velocities (from - 120 degrees s(-1) under eccentric conditions to 240 degrees s(-1) under concentric conditions), and held maximal and submaximal isometric actions. Under all conditions, the myoelectric activities (EMG) of the biceps and the triceps brachii muscles were recorded and quantified as the RMS value. Eccen…

Co-activation and tension-regulating phenomena during isokinetic knee extension in sedentary and highly skilled humans.

The aim of this study was to examine isokinetic torque produced by highly skilled (HS) and sedentary (S) human subjects, during knee extension, during maximal voluntary and superimposed electrical activation. To verify the level of activation of agonist (vastus lateralis, VL, and vastus medialis, VM) and antagonist muscles (semi-tendineous, ST), during maximal voluntary activation, their myo-electrical activities were detected and quantified as root mean square (rms) amplitude. Ten HS and ten S subjects performed voluntary and superimposed isometric actions and isokinetic knee extensions at 14 angular velocities (from -120 to 300 degrees*s(-1)). The rms amplitude of each muscle was normaliz…

Changes in isokinetic torque and muscular activity of elbow flexors muscles with age

This study examined the influence of aging on torque-angular velocity relationships for elbow flexion and the corresponding muscular activity levels in order to target the mechanisms involved in the eccentric muscle action in older adults. Maximal constant angular torque (CAT) at 90 degrees was measured at different angular velocities for concentric (CON; 60, 120, 180, 240 degrees s(-1)), isometric (ISO) and eccentric (ECC; -60, -120 degrees s(-1)) elbow flexor muscle actions in older (OG; 6 females and 4 males, 64-82 years) and young adult subjects (YG; 6 females, 6 males, 19-24 years) on an isokinetic dynamometer. Myoelectrical activity was quantified on biceps and triceps muscles, using …

Postactivation potentiation in human knee extensors during dynamic passive movements.

Purpose: Postactivation potentiation (PAP), i.e., the increase in twitch torque following a maximal voluntary conditioning contraction, has been shown to depend on muscle contractile conditions (e.g., muscle length). Few studies, however, have investigated the extent of twitch PAP under dynamic conditions in human subjects. Therefore, the aim of the present experiment was to test the twitch PAP during passive dynamic movements following isometric conditioning contractions on nine healthy men. Methods: Maximal twitches were evoked on the knee extensor muscles before and exactly 5 s after a 3-s conditioning maximal voluntary isometric contraction. PAP was determined at a constant joint angle …

La Relation Couple-Vitesse Angulaire Chez le Sujet Entraine

Velocity-specific training in elbow flexors.

The purpose of this study was to show that velocity-specific training may be implicated in modifications in the level of coactivation of agonist and antagonist muscles. Healthy males (n = 20) were randomly placed in to two groups: one group trained using concentric contractions (n = 12), the other was an untrained control group (n = 8). The training group underwent unilateral resistance training at a level of 35 (5)% of a one-repetition maximal contraction of the elbow flexors, executed at maximal angular velocity. Training sessions consisted of six sets of eight consecutive elbow flexions, three times per weak for a total of seven weeks. The velocity of the ballistic movements executed dur…

The influence of ageing on the force-velocity-power characteristics of human elbow flexor muscles.

Abstract The purpose of this study was to quantify the effects of ageing on the maximal power ( P max ) of the elbow flexor muscles and to determine the impact of velocity on the loss of power in older people. Sixteen elderly subjects (7 men and 9 women, age range 61–78 years) and 17 young subjects (11 men and 6 women, age range 18–27 years) participated in this study. Maximal elbow flexions were performed against increasing inertia. The maximal force ( F max ), maximal shortening velocity ( V max ), P max , dynamic constants ( a , b and a / F max ), optimal force ( F opt ), optimal velocity ( V opt ) and V opt / V max were determined from Hill's equation. Myoelectrical activity (EMG) of th…

The Effects of Electromyostimulation Training and Basketball Practice on Muscle Strength and Jumping Ability

The aim of this study was to investigate the influence of a 4-week electromyostimulation training program on the strength of the knee extensors and the vertical jump performance of 10 basketball players. Electromyostimulation sessions were carried out 3 times weekly; each session consisted of 48 contractions. Testing was carried out before and after the electromyostimulation training program (week 4) and once more after 4 weeks of normal basketball training (week 8). At week 4, isokinetic strength increased significantly (p < 0.05) at eccentric and high concentric velocities (between 180 and 360 x s(-1)); this was not the case for low concentric velocities (60 and 120 degrees x s(-1)). Elec…

Activation of human quadriceps femoris during isometric, concentric, and eccentric contractions.

Maximal and submaximal activation level of the right knee-extensor muscle group were studied during isometric and slow isokinetic muscular contractions in eight male subjects. The activation level was quantified by means of the twitch interpolation technique. A single electrical impulse was delivered, whatever the contraction mode, on the femoral nerve at a constant 50° knee flexion (0° = full extension). Concentric, eccentric (both at 20°/s velocity), and isometric voluntary activation levels were then calculated. The mean activation levels during maximal eccentric and maximal concentric contractions were 88.3 and 89.7%, respectively, and were significantly lower ( P &lt; 0.05) with respe…

The influence of electrostimulation on mechanical and morphological characteristics of the triceps surae.

The present study assessed the effects of training using electrostimulation of muscle (EMS) on the torque-angular velocity and torque-angle relationships, and the cross-sectional area (CSA) of the triceps surae. Twelve physical education students, divided into two groups (6 controls, 6 experimental), participated in the experiment. The EMS sessions were undertaken using a 'Complex-type' stimulator. Flexible elastomer electrodes were used. The current used discharged pulses lasting for 200 microseconds at a frequency of 70 Hz. The durations of contraction and rest were 5 and 15 s, respectively. The session lasted for 10 min for each muscle. The training regimen was three sessions per week fo…