Single-leg Exercise Research Articles

전신진동(whole body vibration) 및 한쪽 다리 등속성 운동이 동맥경직도 및 대퇴직근 경직도에 미치는 영향

This study is in order to observe the changes of arterial and muscle stiffness after iso-kinetic single leg exercise and whole body vibration application. In a cross-over design, 9 young (19.5±1.4years) healthy males were assigned to whole body vibration (WBV) treatment group and control (complete rest) group with a week interval. Each Subject conducted iso-kinetic knee flexion and extension exercise by dominant leg at180°/sec, 10 bouts, and 10 sets (Biodex system 4, Medical System Inc, USA). The WBV session consisted of 10 sets of vibration (frequency, 26 Hz) for 60s with 60s of rest between sets. Cardio-ankle vascular index (CAVI) and ankle-brachial index (ABI), as index of arterial stiffness, were measured by VaSera CAVI instrument (Fukuda Denshi Co., Ltd., Tokyo, Japan) before, right after exercise and recovery 20min. In order to measure the mechanical properties like muscle stiffness and elasticity, MyotonPro (Myoton AS, Tallinn, Estonia) was applied to muscle belly of rectus femoris at the same time point. From the Myoton measurement, Three indexes (Frequency, Logarithmic Decrement and Dynamic Stiffness) were obtained. The results are as follows: 1. No significant difference in rectus femoris muscle and arterial stiffness index were found between WBV and control group at all the time point. 2. ABI was significantly lower in exercised leg than non-exercised leg immediately after exercise (p.05), although ABI decreased significantly in both legs after exercise (p.05). 3. CAVI showed no significant difference between exercised leg and the non-exercised leg. 4. The muscle tension, stiffness increased significantly in exercised leg than non-exercised leg (p.05) while elasticity decreased significantly in exercised leg than non-exercised leg immediately after exercise (p.05). These results suggest that iso-kinetic-leg exercise may have effect on the changes of both arterial and muscle stiffness index of non-exercised leg as well as exercised leg.

Comparison Between Unilateral and Bilateral Plyometric Training on Single and Double Leg Jumping Performance

The phenomenon of bilateral deficit in jumping implies that greater muscle power can be developed when performing maximal single leg jumps, compared with two-leg jumps. Thus, it may be hypothesized that training with single leg plyometric exercises would be more effective compared to an equivalent volume of double leg plyometric training. PURPOSE: To compare the effects of unilateral and bilateral plyometric training on single and double leg jumping performance. METHODS: Fifteen moderately trained subjects (age: 19.6±2.1 yrs, height: 172±9 cm, body mass: 65.6±10.6 kg) were randomly assigned to either a unilateral (U, n=7) or a bilateral group (B, n=8). Both groups performed maximal effort plyometric leg exercises two times per week for 6 weeks (6 exercises per session, 3 sets of 10 repetitions per exercise), as well as 3 sets of knee extensions and flexions at 70%-90% of their 1 repetition maximum. The U group performed all plyometric and knee flexion/extension exercises with both legs, while the B group performed half the repetitions with each leg, so that the total exercise volume was the same. Jumping performance was assessed by double and single leg countermovement jumps (CMJ) and drop jumps (DJ) from 30 cm, measured using an optical measurement system (Optojump). Reactive strength index (RSI) was calculated from DJ data (jump height and ground contact time). Results were analyzed using a 2 x 2 ANOVA with repeated measures in one factor and Tukey’s post-hoc test. RESULTS: CMJ with both legs significantly improved equally in the U and B groups by 12.1±7.2% and 11.0±5.5% (p<0.001), respectively. However, single-leg CMJ, quantified as the sum of dominant and non-dominant single leg CMJ, only improved in the U group (19.0±7.1%, p<0.001) and was unchanged in the B group (3.4±8.4%, p=0.80). Similarly, RSI for single leg only improved in the U group (from 0.95±0.21 to 1.17±0.25 m·s-1, p=0.002), but not in the B group. CONCLUSIONS: Plyometric training with single leg exercises was more effective in increasing both single and double-leg jumping performance, compared to bilateral training.

Exercise Increases Human Skeletal Muscle Insulin Sensitivity via Coordinated Increases in Microvascular Perfusion and Molecular Signaling

Insulin resistance is a major health risk, and although exercise clearly improves skeletal muscle insulin sensitivity, the mechanisms are unclear. Here we show that initiation of a euglycemic-hyperinsulinemic clamp 4 h after single-legged exercise in humans increased microvascular perfusion (determined by contrast-enhanced ultrasound) by 65% in the exercised leg and 25% in the rested leg (P < 0.05) and that leg glucose uptake increased 50% more (P < 0.05) in the exercised leg than in the rested leg. Importantly, infusion of the nitric oxide synthase inhibitor l-NG-monomethyl-l-arginine acetate (l-NMMA) into both femoral arteries reversed the insulin-stimulated increase in microvascular perfusion in both legs and abrogated the greater glucose uptake in the exercised compared with the rested leg. Skeletal muscle phosphorylation of TBC1D4 Ser318 and Ser704 and glycogen synthase activity were greater in the exercised leg before insulin and increased similarly in both legs during the clamp, and l-NMMA had no effect on these insulin-stimulated signaling pathways. Therefore, acute exercise increases insulin sensitivity of muscle by a coordinated increase in insulin-stimulated microvascular perfusion and molecular signaling at the level of TBC1D4 and glycogen synthase in muscle. This secures improved glucose delivery on the one hand and increased ability to take up and dispose of the delivered glucose on the other hand.

Effects of a Strength Training Session After an Exercise Inducing Muscle Damage on Recovery Kinetics

Abaïdia, A-E, Delecroix, B, Leduc, C, Lamblin, J, McCall, A, Baquet, G, and Dupont, G. Effects of a strength training session after an exercise inducing muscle damage on recovery kinetics. J Strength Cond Res 31(1): 115-125, 2017-The purpose of this study was to investigate the effects of an upper-limb strength training session the day after an exercise inducing muscle damage on recovery of performance. In a randomized crossover design, subjects performed the day after the exercise, on 2 separate occasions (passive vs. active recovery conditions) a single-leg exercise (dominant in one condition and nondominant in the other condition) consisting of 5 sets of 15 eccentric contractions of the knee flexors. Active recovery consisted of performing an upper-body strength training session the day after the exercise. Creatine kinase, hamstring strength, and muscle soreness were assessed immediately and 20, 24, and 48 hours after exercise-induced muscle damage. The upper-body strength session, after muscle-damaging exercise accelerated the recovery of slow concentric force (effect size = 0.65; 90% confidence interval = -0.06 to 1.32), but did not affect the recovery kinetics for the other outcomes. The addition of an upper-body strength training session the day after muscle-damaging activity does not negatively affect the recovery kinetics. Upper-body strength training may be programmed the day after a competition.

The role of muscle sympathetic nerve activity in limiting exercise capacity in heart failure.

The role of muscle sympathetic nerve activity in limiting exercise capacity in heart failure.

Injury of Peripheral Muscles in Smokers with Chronic Obstructive Pulmonary Disease

Muscle injury has clinical relevance in diseased individuals because it is associated with muscle dysfunction in terms of decreased strength and/or endurance. This study was aimed at answering three questions: whether the presence of chronic obstructive pulmonary disease (COPD) is associated with peripheral muscle injury; whether muscle injury is associated with some of the relevant functional impairment in the muscles; and whether muscle injury can be solely justified by deconditioning. Twenty-one male COPD patients were eligible for the study. Seven healthy volunteers recruited from the general population were included as controls. Function of the quadriceps muscle was assessed through specific single-leg exercise (strength and endurance). Cellular (light microscopy) and subcellular (electron microscopy) techniques were used to evaluate muscle injury on biopsies from the vastus lateralis muscle. Signs of injury were found in muscles from both control and COPD patients, not only in cases showing severe airflow obstruction but also in the mild or moderate stages of the disease. Current smoking and presence of COPD were significantly associated with increased injury of the muscle as assessed by light and electron microscopy techniques. The authors conclude that peripheral muscle injury is evident in mild, moderate, and severe stages of COPD even in the absence of respiratory failure, hypercapnia, chronic steroid treatment, low body weight, or some coexisting disease. These findings support the theory that systemic factors with deleterious effect are acting on peripheral muscles of smokers with COPD, increasing the susceptibility of the muscle fibers to membrane and sarcomere injury.

Effect of transcutaneous electrical muscle stimulation on muscle volume in patients with septic shock*

Intensive care unit admission is associated with muscle wasting and impaired physical function. We investigated the effect of early transcutaneous electrical muscle stimulation on quadriceps muscle volume in patients with septic shock. Randomized interventional study using a single-legged exercise design with the contralateral leg serving as a paired control. A mixed 18-bed intensive care unit at a tertiary care university hospital. Eight adult male intensive care unit patients with septic shock included within 72 hrs of diagnosis. After randomization of the quadriceps muscles, transcutaneous electrical muscle stimulation was applied on the intervention side for 7 consecutive days and for 60 mins per day. All patients underwent computed tomographic scans of both thighs immediately before and after the 7-day treatment period. The quadriceps muscle was manually delineated on the computed tomography slices, and muscle volumes were calculated after three-dimensional reconstruction. Median age and Acute Physiology and Chronic Health Evaluation II score were 67 years (interquartile range, 64-72 years) and 25 (interquartile range, 20-29), respectively. During the 7-day study period, the volume of the quadriceps muscle on the control thigh decreased by 16% (4-21%, p=.03) corresponding to a rate of 2.3% per day. The volume of the stimulated muscle decreased by 20% (3-25%, p=.04) corresponding to a rate of 2.9% per day (p=.12 for the difference in decrease). There was no difference in muscle volume between the stimulated and nonstimulated thigh at baseline (p=.10) or at day 7 (p=.12). The charge delivered to the muscle tissue per training session (0.82 [0.66-1.18] coulomb) correlated with the maximum sequential organ failure assessment score. We observed a marked decrease in quadriceps volume within the first week of intensive care for septic shock. This loss of muscle mass was unaffected by transcutaneous electrical muscle stimulation applied for 60 mins per day for 7 days.

Systemic and Pulmonary Oxidative Stress After Single-Leg Exercise in COPD

Our aim for this study was to disentangle the contribution of muscular vs pulmonary oxidative stress during endurance exercise in patients with COPD. Fifteen COPD patients and 10 healthy age-matched control subjects performed a continuously submaximal single-leg ergometer test (40% of peak workload) for 20 min or until they stopped (muscle endurance [Tlim]). Venous blood, urine samples, and exhaled breath condensate were sampled before, immediately after, and 2 h after exercise. Tlim was lower in COPD patients than in control subjects (p < 0.01). No exercise-induced systemic inflammation (ie, no raised levels of interleukin-6 or tumor necrosis factor-alpha) was found in the groups. Urinary malondialdehyde and uric acid levels (p < 0.05) were increased in COPD patients, whereas erythrocyte oxidized glutathione/reduced glutathione levels tended to be increased in COPD patients compared with control subjects after exercise (p = 0.08). Despite the relatively low cardioventilatory response to this localized muscle exercise, hydrogen peroxide levels in breath condensate significantly increased in COPD patients (p < 0.01). Nuclear factor kappaB DNA-binding activity of p50 in peripheral blood monocytes was elevated after exercise in both COPD patients (p < 0.01) and control subjects (p < 0.05), whereas p65 protein levels were not altered. COPD patients showed increased pulmonary and systemic oxidative stress after localized leg muscle exercise compared with healthy control subjects, without evidence of increased levels of systemic inflammation.

Effects of Single-Leg Drop-Landing Exercise from Different Heights on Skeletal Adaptations in Prepubertal Girls: A Randomized Controlled Study

Few studies have explored osteogenic potential of prepubertal populations. We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 prepubertal girls (6 to 10 years) randomly assigned to control (C), low-drop (LD) or high-drop (HD) exercise groups. The latter two groups performed single-leg drop-landings (3 sessions/week-1 and 50 landings/session-1) from 14 cm(LD) and 28 cm(HD) using the nondominant leg. Osteogenic responses were assessed using Dual Energy X-ray Absorptiometry (DXA). Single-leg peak ground-reaction impact forces (PGRIF) in a subsample ranged from 2.5 to 4.4 x body-weight (BW). No differences (p > .05) were observed among groups at baseline for age, stature, lean tissue mass (LTM), leisure time physical activity, or average daily calcium intake. After adjusting for covariates of body mass, fat mass and LTM, no differences were found in bone mineral measures or site-specific bone mineral density (BMD) at the hip and lower leg among exercise or control groups. Combining data from both exercise groups failed to produce differences in bone properties when compared with the control group. No changes were apparent for between-leg differences from baseline to posttraining. In contrast to some reports, our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low-moderate peak ground-reaction impact forces are not osteogenic in the developing prepubertal female skeleton.

Effect of Single-Leg Resistance Exercise on Central and Peripheral Arterial Stiffness

Effect of Single-Leg Resistance Exercise on Central and Peripheral Arterial Stiffness

The effects of low-intensity single-leg exercise on regional arterial stiffness.

We examined the effect of low-intensity single-leg exercise (20 or 30 watt, 5 min) on pulse wave velocity from the femoral to the ankle arteries in 18 young men. After the exercise, the velocity significantly decreased in the exercised leg, but not in the counterpart, suggesting that the decrease in arterial stiffness in the exercised leg was induced mainly by exercise-related regional factors.

Vasoconstriction in active calf persists after discontinuation of combined exercise with high-intensity elbow flexion.

The present study aimed to determine whether vasoconstriction in active calf occurring during combined exercise diminished or persisted when added low- and high-intensity elbow flexion exercise ceased and single leg exercise continued. Six active women (mean age, 21.2 years) participated in this study. During 10-min plantar flexion exercise at 10% of maximum voluntary contraction (MVC), elbow flexion exercise at 10% MVC was added over the 3rd and 4th min. Calf blood flow did not change significantly upon superimposition and cessation of this elbow flexion exercise. However, when elbow flexion exercise at 50% MVC was added during the 7th and 8th min, calf blood flow above the resting value (2.23 +/- 0.23 mL 100 mL-1 min-1) decreased significantly (P < 0.05) from 6.72 +/- 0.87 (6th min) to 5.14 +/- 1.36 mL 100 mL-1 min-1 after 2 min of combined exercise and was accompanied by a similar change in the non-exercising calf blood flow value. The vascular conductance of the exercising calf decreased significantly (P < 0.01) from 6.48 +/- 1.08 (6th min) to 3.11 +/- 1.27 mL 100 mL-1 min-1 mmHg-1 at the end of the 2nd min of combined plantar flexion exercise with elbow flexion exercise at 50% MVC. After elbow flexion exercise at 50% MVC was discontinued and plantar flexion exercise at 10% MVC alone was performed, the vascular conductance in the exercising calf remained significantly low for the next 2 min. These results indicate that the vasoconstriction induced by adding high-intensity arm exercise is persistent, suggesting a major contribution of metabo-receptor-mediated vasoconstriction rather than central command- and mechano-receptor-mediated vasoconstriction.

The role of central command in ventilatory control during static exercise.

The role of central command in the respiratory response to 15 min of rhythmic-static (isometric) exercise was studied in humans. Voluntary exercise (VE) was compared with electrically induced exercise (EE) at three different work intensities, i.e. 5%, 15% and 25% of maximal voluntary contraction. A group of 12 volunteers participated in the study and each of them performed six sessions. A session consisted of at least 5 min rest, 15 min rhythmic-static single leg exercise (4 s contraction/12 s relaxation) and at least 5 min recovery. Force, minute ventilation (VE) and oxygen uptake (VO2) were measured. In EE, both VE and VO2 increased continuously during the entire exercise period after an initial rapid increase at all three work intensities. Correlation between VE and VO2 was highly significant during EE. During all three work intensities of VE, VE and VO2 achieved a steady-state after the initial increase. During VE, VE did not correlate as closely with VO2 as during EE. All these findings indicate that central command was not imperative for an adequate ventilatory response to exercise within all three work intensities investigated. Without the influence of central command, correlation between VE and VO2 was even better than during VE.

Mild exercise impedes glycogen repletion in muscle.

Bicycle ergometric exercise was used to deplete glycogen by either 80 or 35% in the vastus lateralis of both legs. Thereafter, subjects from each group rested or maintained single-leg exercise [20% of maximal O2 consumption (Vo2max) for 4 h. All subjects ingested glucose (1.5 g/kg wt; 20% solution) at min 10-12 and min 130-132 of the 4-h period. With bed rest, significant glycogen increases occurred after exhaustive (+36%; P less than 0.05) and nonexhaustive exercise (+13%; P less than 0.05). With single-leg exercise, 1) a diminished glycogen repletion occurred in exercising (+11%; P less than 0.05) and nonexercising (+15%; P less than 0.05) muscle after exhaustive exercise, or 2) further glycogen loss occurred in exercising (-26%; P less than 0.05) and nonexercising muscle (-19%; P less than 0.05) after nonexhaustive exercise. Within both groups, glycogen concentrations did not differ between exercising and nonexercising muscles (P greater than 0.05). Single-leg exercise, not preceded by exercise, provoked differences in glycogen loss in exercising (-47%) and nonexercising (-24%) muscle (P less than 0.05). These experiments demonstrate that mild exercise 1) impedes glycogen resynthesis or 2) provokes glycogen loss in both exercising and nonexercising muscle. These findings cannot be ascribed to circulating glucose and insulin concentrations in these studies.

Effects of a rapid change in muscle glycogen availability on metabolic and hormonal responses during exercise.

To evaluate the metabolic and hormonal adaptations following a rapid change in muscle glycogen availability, 14 subjects had their muscle glycogen content increased in one leg (IG) and decreased in the other (DG). In group A (n = 7), subjects exercised on a bicycle ergometer at 70% maximal oxygen uptake for 20 min using the DG leg. Without resting these same subjects exercised another 20 min using the IG leg. Subjects in group B (n = 7) followed the same single-leg exercise protocol but in the reverse order. In order to get some information on the time sequence of these possible adaptations, blood samples were collected at rest and at the beginning and the end of each exercise period (min 5, 20, 25, and 40). Results indicated that 5 min after the switch from the DG leg to the IG leg, transient increases in plasma free fatty acids (1.20 to 1.39 meq X 1(-1)) and serum insulin (10.1 to 12 mu X 1(-1)) concentrations occurred. Between minute 25 and 40 of exercise, the DG to IG switch was accompanied by a decrease in free fatty acids and glycerol concentrations as well as an increase in lactate levels. An opposite response was observed in the IG to DG condition during the same time span. Plasma norepinephrine, epinephrine, glucagon, and serum cortisol concentrations were not significantly affected by the leg change. These results suggest a rapid preferential use of muscle glycogen when available and a time lag in the response of the extramuscular substrate mobilization factors.

Continuously Recorded Changes of Thoracic Aortic Blood Flow in Man in Response to Leg Exercise in Supine Position

The constant-rate-injection, indicator-dilution technic was used to determine thoracic aortic blood flow before, during, and after five minutes of single-leg exercise (bicycle ergometer) in five healthy male subjects in the supine position. Resistance to blood flow in the lower body and mean aortic pressure decreased immediately at the onset of exercise, at the same time that thoracic aortic blood flow and heart rate increased. There was a further slow rise of heart rate, mean aortic pressure, and thoracic aortic blood flow along with a decrease of lower body resistance until fairly stable levels were reached after five minutes of exercise. After five and ten minutes' rest all values tended to return toward those observed in the control state. These data are consistent with the concept that baroreceptor activity may play an important part in the early cardiovascular responses to exercise in man. Most of the cardiovascular response to this exercise occurred in the first 30 seconds.