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At least 19 recordsLinked to original sources

PubMed2007

Effects of muscle strength training and megestrol acetate on strength, muscle mass, and function in frail older people.

OBJECTIVES: To determine the independent and combined effects of progressive resistance muscle strength training (PRMST) and megestrol acetate (MA) on strength, muscle mass, and function in older recuperative care patients. DESIGN: Double-blind, randomized, controlled intervention using a two-by-two factorial design and conducted between 1999 and 2001. SETTING: University-affiliated Department of Veterans Affairs hospital. PARTICIPANTS: Twenty-nine patients (mean age 79.4 +/- 7.4, 90% white) aged 65 and older and had recent functional decline. INTERVENTIONS: After randomization to one of four treatment groups (low-resistance exercises plus 800 mg per day of MA or a placebo or high-intensity PRMST plus 800 mg/d of MA or placebo), subjects received training and the drug or placebo for 12 weeks. MEASUREMENTS: Change in muscle strength, mid-thigh muscle area, and aggregate functional performance score as assessed using analysis of covariance. RESULTS: Five subjects withdrew from the study before its completion. Based on intent-to-treat analyses, subjects who received high-intensity PRMST and placebo experienced the greatest strength gains. The addition of MA was associated with worse outcomes than with high-intensity exercise training alone, especially with regard to the leg exercises. Post hoc analysis demonstrated that subjects who received high-intensity PRMST and placebo experienced significantly greater percentage increases in leg strength than subjects in either of the MA treatment groups (P<.05 for each comparison). There was also a significant negative effect of MA on physical function. In general, subjects who received MA experienced a deterioration in aggregate physical function scores, whereas the remaining subjects improved (-0.80+/-0.40 vs 0.48+/-0.41, P=.04). There was not a significant interaction between exercise and MA for any outcome. CONCLUSION: High-intensity PRMST is a safe and well-tolerated exercise regimen for frail elderly patients. The addition of MA appears to blunt the beneficial effects of PRMST, resulting in less muscle strength and functional performance gains.

Aged↗

PubMed1998

An 8-year longitudinal study of muscle strength, muscle fiber size, and dynamic electromyogram in individuals with late polio.

Twenty-one subjects with polio 24 to 51 years prior to the first examination were studied on three occasions, each 4 years apart with measurements of muscle strength and endurance for knee extension, macro EMG, and muscle biopsy from vastus lateralis. On average the muscle strength decreased during the 8-year follow-up by 9-15%. Endurance decreased during the observation period. The muscle fiber area was markedly increased in most subjects. There was a decrease in the capillarization during the follow-up. Macro EMG was increased in all subjects (range 3-42 times control) and increased in 20 legs during the 8-year follow-up, but showed a decrease in 8 of 9 legs with an approximative breakpoint when macro MUPs were around 20 times the normal size. Thus, evidence of on-going denervation/reinnervation as well as of failing capacity to maintain large motor units was demonstrated. SFEMG showed a moderate degree of disturbed neuromuscular transmission.

Adult↗

PubMed2000

Changes in muscle strength, muscle fibre size and myofibrillar gene expression after immobilization and retraining in humans.

1. Changes in muscle strength, vastus lateralis fibre characteristics and myosin heavy-chain (MyoHC) gene expression were examined in 48 men and women following 3 weeks of knee immobilization and after 12 weeks of retraining with 1866 eccentric, concentric or mixed contractions. 2. Immobilization reduced eccentric, concentric and isometric strength by 47 %. After 2 weeks of spontaneous recovery there still was an average strength deficit of 11 %. With eccentric and mixed compared with concentric retraining the rate of strength recovery was faster and the eccentric and isometric strength gains greater. 3. Immobilization reduced type I, IIa and IIx muscle fibre areas by 13, 10 and 10 %, respectively and after 2 weeks of spontaneous recovery from immobilization these fibres were 5 % smaller than at baseline. Hypertrophy of type I, IIa and IIx fibres relative to baseline was 10, 16 and 16 % after eccentric and 11, 9 and 10 % after mixed training (all P < 0.05), exceeding the 4, 5 and 5 % gains after concentric training. Type IIa and IIx fibre enlargements were greatest after eccentric training. 4. Total RNA/wet muscle weight and ty I, IIa and IIx MyoHC mRNA levels did not change differently after immobilization and retraining. Immobilization downregulated the expression of type I MyoHC mRNA to 0.72-fold of baseline and exercise training upregulated it to 0.95 of baseline. No changes occurred in type IIa MyoHC mRNA. Immobilization and exercise training upregulated type IIx MyoHC mRNA 2.9-fold and 1.2-fold, respectively. For the immobilization segment, type I, IIa and IIx fibre area and type I, IIa and IIx MyoHC mRNA correlated (r = 0.66, r = 0.07 and r = -0.71, respectively). 5. The present data underscore the role muscle lengthening plays in human neuromuscular function and adaptation.

Adult↗

PubMed2003

Muscle atrophy in patients receiving hemodialysis: effects on muscle strength, muscle quality, and physical function.

BACKGROUND: Dialysis patients are less active and have reduced functional capacity compared to individuals with normal renal function. Muscle atrophy and weakness may contribute to these problems. This investigation was undertaken to quantify the extent of atrophy in the lower extremity muscles, to determine whether defects in muscle specific strength (force per unit mass) or central nervous system (CNS) activation are present, and to assess the relationship between muscle size and physical performance in a group of patients on hemodialysis. METHODS: Thirty-eight dialysis subjects (aged 55 +/- 15 years) and nineteen healthy sedentary controls (aged 55 +/- 13 years) were enrolled. Magnetic resonance imaging of the lower leg was used to determine the total cross-sectional area (CSA) and the area of contractile and non-contractile tissue of the ankle dorsiflexor muscles. Isometric dorsiflexor strength was measured during a maximal voluntary contraction with and without superimposed tetanic stimulation (N = 22 for dialysis subjects, N = 12 for controls). Physical activity was measured by accelerometry, and gait speed was recorded as a measure of physical performance. RESULTS: Dialysis subjects were weaker, less active, and walked more slowly than controls. Total muscle compartment CSA was not significantly different between dialysis subjects and controls, but the contractile CSA was smaller in the dialysis patients even after adjustment for age, gender, and physical activity. Central activation and specific strength were normal. Gait speed was correlated with contractile CSA. CONCLUSIONS: Significant atrophy and increased non-contractile tissue are present in the muscle of patients on hemodialysis. The relationship between contractile area and strength is intact in this population. Muscle atrophy is associated with poor physical performance. Thus, interventions to increase physical activity or otherwise address atrophy may improve performance and quality of life.

Adult↗

PubMed1995

[Muscle strength and muscle blood flow of the quadriceps muscle].

This study was conducted to measure muscle blood flow changes during increased muscle strength in order to determine what characteristic parameters of muscle strength were most closely correlated with increased muscle blood flow. The muscle blood flow and muscle strength in the quadriceps femoris were measured simultaneously during isokinetic extension of the knee joints in two groups--one with knee-joint-disease and the other of healthy volunteers. Muscle blood flow was measured by the heated thermocouple technique, while parameters of muscle strength were evaluated utilizing curves calculated by a Cybex II. The test results showed a positive correlation between parameters of muscle strength (peak torque, total work and average power) and peak blood flow. However, both the muscle strength and the muscle blood flow values were less in the group with knee joint disease than in the group of healthy volunteers. In both groups, the muscle blood flow was greatest when the knee was extended at an increased angular velocity. Although the muscle blood flow was greatest at this time, only the parameter of average power increased while the parameter of peak torque and total work decreased. As a result, the average power was correlated most closely with the increased muscle blood flow. In patients with a knee joint disease, the increase in the muscle blood flow was much higher than expected despite the fact that there was little increase in average power during knee movement at an increased angular velocity. It appeared that the pathological condition in these patients' quadriceps femoris required increased blood flow despite an inability of the muscle to perform increased muscle work.

Adolescent↗

PubMed1988

Muscle strength and muscle endurance of middle-aged women and men associated to type, duration and intensity of muscular load at work.

Muscle strength and muscle endurance in groups with different occupational muscular load was studied among 60 women and 69 men. The mean age of the subjects was 52.0 +/- 3.4 years. Isometric grip and trunk strength were measured on dynamometers, and dynamic muscle endurance by sit-ups. A job analysis was done with the AET method including the assessment of intensity, duration and type of muscular work of each subject. According to the job analysis, the subjects were classified into groups with low or high muscular load at work. The maximal isometric hand grip strength of women with a load classified as long duration of static or dynamic load on the hands at work was 86 and 88%, respectively of the strength of those with a load of short duration. The women with high intensity in static work had a grip strength of 86% of those with low intensity. These differences in strength among women between the high and low load groups were statistically significant (P less than 0.05). No other statistically significant differences in muscle strength or muscle endurance between the high and low work load groups were found, although the high work load group had systematically the lowest muscle strength and muscle endurance in almost all comparisons. Muscle strength and muscle endurance was, however, not a discriminating factor between the group classifications of static and dynamic work. The results indicated that the muscle strength and muscle endurance of middle-aged employees was systematically lower among those with high muscular load compared to those with low load at work.

Female↗

PubMed2002

Hip muscle strength and muscle cross sectional area in men with and without hip osteoarthritis.

OBJECTIVE: To study the hip muscle strength and cross sectional area (CSA) in men with hip osteoarthritis (OA) compared to age and sex matched healthy controls. METHODS: Based on the American College of Rheumatology criteria regarding classification of hip OA, 27 men (aged 47-64 yrs) with unilateral or bilateral hip OA and 30 age matched randomly selected healthy male controls were studied. The maximal isometric hip abductor, adductor, flexor, and extensor strength (Nm) at 0 degree of hip flexion in the supine position was determined with a dynamometer. The isokinetic hip flexion and extension strength (peak torque, Nm) was determined using angular velocities of 60 degrees /s and 120 degrees /s. The subjective severity of hip pain was rated by visual analog scale prior to the muscle strength test. CSA of the pelvic and thigh muscles was measured from magnetic resonance images. RESULTS: The reliability of intraclass correlation coefficients for repeated measures of muscle strength varied from 0.70 to 0.94 in controls and from 0.84 to 0.98 in subjects with OA. Hip isometric adductor and abductor strength was 25% and 31% lower (p < 0.001) in OA subjects than in controls, respectively. The hip isometric and isokinetic flexion strength was 18-22% lower (p < 0.01) in OA subjects than in controls, but extension strength did not differ between groups. In OA subjects, the hip flexion and extension isometric and isokinetic strength values were 13-22% lower (p < 0.05) on the more deteriorated side compared to the better side. CSA of the pelvic and thigh muscles did not differ between the groups. However, in OA subjects, the CSA of the pelvic and thigh muscles was 6-13% less (p < 0.05 to < 0.001) on the more severely affected hip compared to the better hip. CONCLUSION: Men with hip OA have significantly lower abduction, adduction, and flexion muscle strength than controls. The decrease of muscle size and hip pain may contribute to the decrease of muscle strength in hip OA. Other possible underlying causes of the muscle weakness need to be studied.

Anatomy, Cross-Sectional↗

PubMed2002

Quantitative analysis of the effect of lumbar orthosis on trunk muscle strength and muscle activity in normal subjects.

We studied the effect of lumbar orthosis on trunk muscle strength and muscle activity during flexion-extension bending of the trunk in 31 male volunteers. Trunk muscle strength was measured with a kinetic measurement system. Peak torque was calculated by using the mean torque of five repetitions. Trunk muscle activity was measured with commercially available equipment that has portable EMG data-collection units. The maximum level of the EMG signal was evaluated by employing the analyzing part of the computer's measuring program. With the application of the lumbar orthosis, the strength of the abdominal muscle and the back muscle increased; conversely, the activities of both muscles were decreased significantly. This might imply that lumbar orthosis reduces the load of the trunk muscles during performance.

Adult↗

PubMed2005

Muscle mass, muscle strength, and muscle fat infiltration as predictors of incident mobility limitations in well-functioning older persons.

BACKGROUND: Lower muscle mass has been correlated with poor physical function; however, no studies have examined this relationship prospectively. This study aims to investigate whether low muscle mass, low muscle strength, and greater fat infiltration into the muscle predict incident mobility limitation. METHODS: Our study cohort included 3075 well-functioning black and white men and women aged 70-79 years participating in the Health, Aging, and Body Composition study. Participants were followed for 2.5 years. Muscle cross-sectional area and muscle tissue attenuation (a measure of fat infiltration) were measured by computed tomography at the mid-thigh, and knee extensor strength by using a KinCom dynamometer. Incident mobility limitation was defined as two consecutive self-reports of any difficulty walking one-quarter mile or climbing 10 steps. RESULTS: Mobility limitations were developed by 22.3% of the men and by 31.8% of the women. Cox's proportional hazards models, adjusting for demographic, lifestyle, and health factors, showed a hazard ratio of 1.90 [95% confidence interval (CI), 1.27-2.84] in men and 1.68 (95% CI, 1.23-2.31) in women for the lowest compared to the highest quartile of muscle area (p <.01 for trend). Results for muscle strength were 2.02 (95% CI, 1.39-2.94) and 1.91 (95% CI, 1.41-2.58), p <.001 trend, and for muscle attenuation were 1.91 (95% CI, 1.31-2.83) and 1.68 (95% CI, 1.20-2.35), p <.01 for trend. When included in one model, only muscle attenuation and muscle strength independently predicted mobility limitation (p < .05). Among men and women, associations were similar for blacks and whites. CONCLUSION: Lower muscle mass (smaller cross-sectional thigh muscle area), greater fat infiltration into the muscle, and lower knee extensor muscle strength are associated with increased risk of mobility loss in older men and women. The association between low muscle mass and functional decline seems to be a function of underlying muscle strength.

Aged↗

PubMed2007

Muscle strength and muscle training after stroke.

For many individuals who have experienced a stroke, muscle weakness is the most prominent impairment. Both the theoretical and statistical relationships between muscle weakness and performance at functional activities suggest that weakness may be an appropriate target for therapeutic interventions. Researchers investigating the outcomes of strengthening regimens after stroke have routinely shown that resistance exercise leads to increased muscle strength, but that strength is typically measured using the same maneuvers that were used in training. Evidence supporting the use of strengthening regimens to reduce limitations in functional activity is equivocal.

Activities of Daily Living↗

PubMed1987

Simple tests for surveying muscle strength and muscle stiffness in sportsmen.

Thirty-nine elite runners were examined by Cybex II for thigh muscle strength. In addition, the maximal abduction, flexion and extension in the hip, dorsal flexion in the ankle, standing five steps, long and vertical jump, and side and front split were measured. For the latter five tests, an ordinary measuring tape was used. To establish reference values, 111 district level runners and 24 keep-fit joggers were examined by the three jump tests and the side and front split. Twenty randomly selected runners were examined twice to determine the reproducibility. The mean CV% was 1.9 +/- 1.4. There was a statistically significant correlation between the results in the vertical jump, the standing five steps, and long jump and muscle strength (P less than 0.001), in particular as to the values in the higher angle velocity. Furthermore, there was a correlation (P less than 0.001) between the results in side and front split and the hip. There was a covariation between the three ranges of motion, suggesting that stiffness in the hip was a general condition involving all directions of movements. The sensitivity for the jump tests and the side/front splits was 75%-91%. The specificity for the same test varied between 70% and 100%.

Adult↗

PubMed2003

Low vitamin D and high parathyroid hormone levels as determinants of loss of muscle strength and muscle mass (sarcopenia): the Longitudinal Aging Study Amsterdam.

The age-related change in hormone concentrations has been hypothesized to play a role in the loss of muscle mass and muscle strength with aging, also called sarcopenia. The aim of this prospective study was to investigate whether low serum 25-hydroxyvitamin D (25-OHD) and high serum PTH concentration were associated with sarcopenia. In men and women aged 65 yr and older, participants of the Longitudinal Aging Study Amsterdam, grip strength (n = 1008) and appendicular skeletal muscle mass (n = 331, using dual-energy x-ray absorptiometry) were measured in 1995-1996 and after a 3-yr follow-up. Sarcopenia was defined as the lowest sex-specific 15th percentile of the cohort, translating into a loss of grip strength greater than 40% or a loss of muscle mass greater than 3%. After adjustment for physical activity level, season of data collection, serum creatinine concentration, chronic disease, smoking, and body mass index, persons with low (<25 nmol/liter) baseline 25-OHD levels were 2.57 (95% confidence interval 1.40-4.70, based on grip strength) and 2.14 (0.73-6.33, based on muscle mass) times more likely to experience sarcopenia, compared with those with high (>50 nmol/liter) levels. High PTH levels (>or=4.0 pmol/liter) were associated with an increased risk of sarcopenia, compared with low PTH (<3.0 pmol/liter): odds ratio = 1.71 (1.07-2.73) based on grip strength, odds ratio = 2.35 (1.05-5.28) based on muscle mass. The associations were similar in men and women. The results of this prospective, population-based study show that lower 25-OHD and higher PTH levels increase the risk of sarcopenia in older men and women.

Absorptiometry, Photon↗

PubMed1995

The influence of aging on muscle strength and muscle fiber characteristics with special reference to eccentric strength.

It is well established that aging seriously reduces isometric and concentric muscle strength due to atrophy, deterioration of mechanical properties, and motor unit loss. However, there is limited information on the impact of aging on eccentric strength despite the fact that such forces play an equally important role during daily activities. The purpose of this study was to examine the influence of aging on three expressions of muscle strength (isometric, concentric, and eccentric) in relation to muscle fiber characteristics, with special emphasis on eccentric force. Sedentary but healthy men (age range 18-80 years, n = 60) and women (20-74 years, n = 30) were tested for maximal effort isometric, concentric, and eccentric (1.05, 2.09, 3.14 rads.s-1) quadriceps strength, body composition, and muscle fiber characteristics of the vastus lateralis (men only). There was a significant (p < .05) approximately 30 N per decade decline in isometric and concentric forces, but only 9 N per decade reduction in eccentric strength. There was a significant reduction in Type II muscle fiber area with aging (p < .05). Isometric, eccentric, and concentric force correlated r = .33, r = .32 (p < .05), and r = .12 (p > .05) with Type II muscle fiber area, respectively. The correlation between age and fat-free mass/force ratio ranged from r = .39 to .43 in men and r = .27 to .50 in women. The data suggest a relative preservation of eccentric strength with aging in men and women that seems to be independent of muscle mass or muscle fiber type or size.

Adolescent↗

PubMed2004

Long-term outcome of muscle strength in ulnar and median nerve injury: comparing manual muscle strength testing, grip and pinch strength dynamometers and a new intrinsic muscle strength dynamometer.

OBJECTIVE: To compare the outcome of muscle strength with manual muscle strength testing grip and pinch strength measurements and a dynamometer which allows for measurements of the intrinsic muscles of the hand in isolation (the Rotterdam Intrinsic Hand Myometer, RIHM). METHODS: Thirty-four patients more than 2 years after ulnar and/or median nerve injury. Muscle strength was evaluated using manual muscle strength testing (MMST), grip, pinch and intrinsic muscle strength measurements. RESULTS: Manual muscle strength testing showed that most muscles recover to grade 3 or 4. Average grip strength recovery, as percentage of the uninjured hand, was 83%. Pinch strength recovery was 75%, 58% and 39% in patients with ulnar, median and combined nerve injuries, respectively. The RIHM measurements revealed a poor recovery of the ulnar nerve innervated muscles in particular (26-37%). No significant correlation (Pearson) was found between the measurements of the RIHM and grip strength. Pinch strength was significantly correlated with strength of the abduction of thumb and opposition of the thumb strength (r 0.55 and 0.72, p = 0.026, 0.002) as measured with the RIHM. CONCLUSION: While manual muscle strength testing and grip strength measurements show a reasonable to good recovery, measurements of the intrinsic muscles by means of the RIHM showed poor recovery of intrinsic muscle strength after peripheral nerve injury. No correlation was found between the recovery of intrinsic muscle strength and grip strength measurements.

Adolescent↗

PubMed1979

Muscle strength and muscle characteristics in monozygous and dizygous twins.

Muscle strength and electrical activity were investigated on 31 pairs of young male and female monozygous (MZ) and dizygous (DZ) twins. The measurements included leg forces, force-time, running velocity, muscular power, maximal integrated electromyographic activity (IEMG) and chronaximetry of the quadriceps muscle group. In each parameter the intrapair variance was computed and the differences were tested between the MZ and DZ twins. The variance ratio (MZ vs. DZ) was statistically significant only for muscular power confirming an earlier finding which has demonstrated a genetic component for the variable. In addition to the various performance variables several key enzymes involved in ATP turnover during muscle contraction and in glucose residue metabolism were analyzed from the muscle biopsy samples (m. vastus lateralis). A genetic component could not be observed in any of their activities or their relationships to performance variables.

Adolescent↗

PubMed2006

Task-oriented progressive resistance strength training improves muscle strength and functional performance in individuals with stroke.

OBJECTIVE: To examine the effectiveness of task-oriented progressive resistance strength training on lower extremity strength and functional performance in chronic stroke subjects. DESIGN: Single-blind, randomized controlled trial. SETTING: Medical centre and district hospital. SUBJECTS: Forty-eight subjects at least one year post stroke. INTERVENTIONS: Participants randomly allocated to two groups, control (n-/24) and experimental (n-/24). Subjects in the control group did not receive any rehabilitation training. Subjects in the experimental group were put on a four-week task-oriented progressive resistance strength training. MAIN MEASURES: Lower extremity muscle strength, gait velocity, cadence, stride length, six-minute walk test, step test, and timed up and go test. RESULTS: Muscle strength significantly improved in the experimental group for strong side muscle groups (ranged from 23.9% to 36.5%) and paretic side muscle groups (ranged from 10.1% to 77.9%). In the control group muscle strength changes ranged from 6.7% gain to 11.2% decline. The experimental group showed significant improvement in all selected measures of functional performance except for the step test. In the control group, the number of repetitions of the step test significantly decreased (-20.3%) with no change in other functional tests. There was a significant difference between groups for muscle strength and all functional measures. The strength gain was significantly associated with gain in the functional tests. CONCLUSIONS: The task-oriented progressive resistance strength training programme could improve lower extremity muscle strength in individuals with chronic stroke and could carry over into improvement in functional abilities.

Aged↗

PubMed2001

A randomized two-year study of the effects of dynamic strength training on muscle strength, disease activity, functional capacity, and bone mineral density in early rheumatoid arthritis.

OBJECTIVE: To evaluate the impact of a 2-year program of strength training on muscle strength, bone mineral density (BMD), physical function, joint damage, and disease activity in patients with recent-onset (<2 years) rheumatoid arthritis (RA). METHODS: In this prospective trial, 70 RA patients were randomly assigned to perform either strength training (all major muscle groups of the lower and upper extremities and trunk, with loads of 50-70% of repetition maximum) or range of motion exercises (without resistance) twice a week; all were encouraged to engage in recreational activities 2-3 times a week. All patients completed training diaries (evaluated bi-monthly) and were examined at 6-month intervals. All were treated with medications to achieve disease remission. Maximum strength of the knee extensors, trunk flexors and extensors, and grip strength was measured with dynamometers. BMD was measured at the femoral neck and lumbar spine by dual x-ray densitometry. Disease activity was determined by the Disease Activity Score, the extent of joint damage by the Larsen score, and functional capacity by the Health Assessment Questionnaire (HAQ); walking speed was also measured. RESULTS: Sixty-two patients (31 per group) completed the study. Strength training compliance averaged 1.4-1.5 times/week. The maximum strength of all muscle groups examined increased significantly (19-59%) in the strength-training group, with statistically significant improvements in clinical disease activity parameters, HAQ scores, and walking speed. While muscle strength, disease activity parameters, and physical function also improved significantly in the control group, the changes were not as great as those in the strength-training group. BMD in the femoral neck and spine increased by a mean +/- SD of 0.51 +/- 1.64% and by 1.17 +/- 5.34%, respectively, in the strength-training group, but decreased by 0.70 +/- 2.25% and 0.91 +/- 4.07% in the controls. Femoral neck BMD in the 17 patients with high initial disease activity (and subsequent use of oral glucocorticoids) remained constantly at a statistically significantly lower level than that in the other 45 patients. CONCLUSION: Regular dynamic strength training combined with endurance-type physical activities improves muscle strength and physical function, but not BMD, in patients with early RA, without detrimental effects on disease activity.

Adult↗

PubMed2005

Influence of maximal muscle strength and intrinsic muscle contractile properties on contractile rate of force development.

'Explosive' muscle strength or contractile rate of force development (RFD) is a term to describe the ability to rapidly develop muscular force, and can be measured as the slope of the torque-time curve obtained during isometric conditions. Previously, conflicting results have been reported regarding the relationship between contractile RFD and various physiological parameters. One reason for this discrepancy may be that RFD in various time intervals from the onset of contraction is affected by different physiological parameters. The aim of the present study was to investigate the relationship between voluntary contractile RFD in time intervals of 0-10, 0-20, ..., 0-250 ms from the onset of contraction and two main parameters: (1) voluntary maximal muscle strength and (2) electrically evoked muscle twitch contractile properties. The main finding was that voluntary RFD became increasingly more dependent on MVC and less dependent on muscle twitch contractile properties as time from the onset of contraction increased. At time intervals later than 90 ms from the onset of contraction maximal muscle strength could account for 52-81% of the variance in voluntary RFD. In the very early time interval (<40 ms from the onset of contraction) voluntary RFD was moderately correlated to the twitch contractile properties of the muscle and was to a less extent related to MVC. The present results suggest that explosive movements with different time spans are influenced by different physiological parameters. This may have important practical implications when designing resistance training programs for specific sports.

Adult↗