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At least 19 recordsLinked to original sources
PubMed1976

Effect of strength training on EMG of human skeletal muscle.

The effects of an 8 weeks period of systematic progressive strength training on the EMG activity of the leg extensor muscles (vastus lateralis and rectus femoris) were investigated in 8 healthy male subjects (22-31 yrs). After training there were indications (n.s.) of a decline in integrated EMG (IEMG) during maximal isometric knee extension as well as in the IEMG vs isometric force relationship. The averaged motor unit potential (AMUP) did not demonstrate any significant changes due to the strength training regimen. In conformity with earlier findings no or only minor alterations were observed in anthropometrics, muscle enzyme activities and fibre composition. The fibre area ratio indicated a specific effect of the training stimuli on the fast twitch muscle fibres. Thus, EMG-analyses, as employed in the present study, did not provide any conclusive additional explanation as to the mechanisms behind the well established gains in muscle strength performance induced by the applied strength training program.

Action Potentials↗
PubMed1979

Adaptations in skeletal muscle following strength training.

Five men were studied before and after 7 wk of isokinetic strength training to determine its effects on muscle enzyme activities and fiber composition. One of the subject's legs was trained using 10 repeated 6-s maximal work bouts, while the other leg performed repeated 30-s maximal knee extension exercise. The total work accomplished by each leg was constant. Training 4 times/wk achieved similar gains in peak torque for both legs at the training velocity (3.14 rad/s) and at slower speeds. Fatigability of the knee extensor muscles, as measured by a 60-s exercise test, was similar in both legs after training. Biopsy specimens showed significant changes in the % of the muscle area composed of type I and IIa fibers as a result of both strength training programs. In terms of muscle enzymes, only the 30 s exercise program resulted in elevated glycolytic, ATP-CP and mitochondrial activities. Despite these changes, none of the parameters measured were found to be related to the gains in either muscle strength or fatigability during maximal isokinetic contractions.

Adaptation, Physiological↗
PubMed1978

Effect of isometric strength training of mechanical, electrical, and metabolic aspects of muscle function.

Monozygous twin pairs (two female and four male) were used in a strength training study so that one member of each pair served as training subject (TS) and the other members as nonexercising controls (CS). TS trained four times a week for 12 weeks with maximal isometric knee extensions of the right leg. The parameters studied included muscle strength, endurance time, electromyographic activity, and activities of several key enzymes in nonoxidative an oxidative muscle metabolism. The results disclosed that in addition to a 20% increase in isometric knee extension strength in the trained leg of TS, an average increase of 11% was observed in strength of TS untrained leg. CS did not demonstrate any change in muscle strength. Training also included an improvement in the maintenance of a static load of 60% of the pretraining maximum. Increase in the maximum integrated electromyographic activity (IEMG) of the rectus femoris muscle occurred concomitantly with the knee extension strength. Traning also caused reduction in the IEMG/tension ratio at submaximal loads indicating a more econimical usage of the rectus femoris muscles. Muscle biopsies taken from the vastus lateralis muscle showed that the enzyme activities of MDH, SDH, and HK were higher, and LDH and CPK lower in the trained leg as compared to the nontrained control leg of TS or to the values of the untrained member of the twin pair. It is concluded that isometric strength training as used in the present study can cause increased recruitment of the availabel motor unit pool, improved efficiency at submaximal loads, and surprisingly also enchancement of the oxidative metabolism in the muscle.

Adolescent↗
PubMed1975

LDH isozymes in skeletal muscles of endurance and strength trained athletes.

Muscle biopsy samples were obtained from arm and leg muscles of endurance and strength trained athletes, respectively. Total LDH activity as well as occurrence and activity of LDH isozymes were determined. Comparing the results from the athletes with those from non-trained subjects with corresponding fibre compositions, it was found that the endurance athletes had a lower total LDH activity, a higher relative activity of the most heart-specific isozymes. LDH (1 + 2), and, on electrophoretic separation, a complete absence of LDH (4 + 5) in both arm and leg muscles. As compared to the untrained material the strength trained athletes tended to have a higher total LDH activity, a similar distribution of relative isozyme activities, and, in the leg muscles, a strong electrophoretic band corresponding to LDH 5, the most skeletal muscle specific isozyme.

Adult↗
PubMed1979

Physiologic effects on adult men of circuit strength training and jogging.

The purpose of this study was to determine the effects of 8 weeks of circuit strength training (CST) followed by 8 weeks of jogging and then 8 weeks, of CST or jogging. During the final 8 weeks, the subjects were randomly assigned to either CST or jogging groups. The subjects (n=16, x age = 29 yrs) exercised 3 days/week. The strength training involved 2 circuits of reciprocal exercises using isokinetic devices with 10 to 15 repetitions/set and 30 seconds of rest between sets. The subjects jogged 3 miles/day during the jogging program. After the initial 8 weeks of CST, significant changes were found in treadmill performance time, maximum oxygen uptake (VO2max), maximum pulmonary ventilation (VEmax), body fat, total skinfold fat, fat weight, lean weight, isotonic bench and leg press, and isokinetic slow speed, fast speed, and power endurance measures. The jogging program elicited significantly greater changes in treadmill performance time and VO2max. Further reductions were found in total skinfolds and waist girth during the jogging program. Leg strength was maintained during jogging but upper body strength was reduced significantly. Physiologic levels were maintained during the final 8 weeks and showed no differences between the CST and jogging groups.

Adult↗
PubMed1976

Effect of strength training on enzyme activities and fibre characteristics in human skeletal muscle.

Progressive strength training was performed 3 times a week for 8 weeks by 14 male students (19-31 yrs.). The training program consisted mainly of dynamic exercises for the leg extensors with maximal or close to maximal loads. The training caused significant improvements in dynamic and isometric strength. One repetition maximum in squats increased with 67%, Sargent jump with 22%, and maximal voluntary isometric contraction (MVC) with 13%, respectively. Body weight and leg muscle circumferences remained unchanged after training, whereas total body potassium, lean body mass and calculated total muscle mass increased, suggesting a change in body composition with training. Muscle biopsies were obtained from vastus lateralis for fibre analyses and determination of enzyme activities. There were no changes in muscle fibre composition or fibre area with training. The activities of Mg2+ stimulated ATPase, creatine phosphokinase and phosphofructokinase remained unchanged, whereas myokinase activity was increased after training from (1.41 to 1.52 moles x 10(-4) x g-1 x min-1, p less than 0.05). After training significant correlations (p less than 0.01) were demonstrated between Mg2+ stimulated ATPase activity and % fast twitch fibres (% FT) (r = 0.67), as well as between myokinase activity and % FT (r = 0.86).

Adenosine Triphosphatases↗
PubMed1979

Achilles tendon injury. 5. A model of isokinetic strength training using biofeedback.

Plantar flexion strength was isokinetically trained under visual biofeedback control in subjects with long standing unilateral soleus muscle myopathy and plantar flexion weakness after Achilles tendon rupture. The rupture had been surgically treated at least one year before training commenced. In the subjects both static and dynamic plantar flexion strengths were normalized as compared to the uninjured leg pre-training. This was accomplished by a) normalization of muscle fibre cross-sectional profile and area within the myopathic muscles, and b) faster achievement of the peak torque during the angular motion. The successful results imply that this training model can be applied when hypotrophy and possibly calf weakness prevail in the aftermath of Achilles tendon rupture.

Achilles Tendon↗
PubMed1978

Variable resistance versus constant resistance strength training in adult males.

Changes in strength, body composition and anthropometric measures for groups training with constant resistance and variable resistance training procedures was compared. Thirty-six male volunteers were randomly assigned to one of three groups: Constant Resistance (CR), Variable Resistance (VR) and Control (C). Strength training was conducted 3 days per week, 45 min per day, for 10 weeks. The results demonstrated that both the CR and the VR groups increased muscular strength. The CR group demonstrated significant increases in strength over the VR group when strength was assessed by CR procedures. Conversely, the VR group demonstrated significant increases in strength over the CR group when strength was assessed by VR procedures. Neither group exhibited superiority over the other relative to changes in body composition and anthropometric measures. The significance of these results is discussed.

Adolescent↗
PubMed1979

The effect of unilateral isokinetic strength training on local adipose and muscle tissue morphology, thickness, and enzymes.

One-leg exercise of 5 weeks duration in 10 healthy middleaged women resulted in a significant increment of muscle force in the exercising leg and in a less, but at some angular velocities also significant, increase in the nonexercising leg. The thickness of subcutaneous tissue measured by ultrasound and skinfold caliper decreased, while muscle thickness increased in the exercising leg only. The increased thickness of muscle tissue was associated with an increase in the relative number and relative fiber area of type II fibers in the exercising leg. The mean fiber area of type IIB fibers increased significantly as well as the activity of lactate dehydrogenase and myokinase. The decrease of thickness of subcutaneous adipose tissue was not associated with a significant decrease in fat cell size and was probably due to geometrical factors secondary to hypertrophy of the underlying muscle. It is concluded that the relationship between lean and fat components of the human thigh is significantly influenced by changes in the activity of the thigh skeletal muscles, but a local dynamic strength training program can hardly be used for local emptying of the fat depot over the exercising muscles.

Adenosine Triphosphatases↗
PubMed1977

Electromyographic and girth considerations relative to strength training.

19 male and 23 female volunteers were tested for surface electromyograms. Girth and skinfold measures were taken at the same location, while cable tensiometer readings indicated quadriceps strength. After a 7-wk. strength improvement program, measures were repeated. Both men and women increased their quadriceps strength. The men's thigh girth significantly increased, whereas the women's did not. Both groups demonstrated significant electromyogram change for a 16-lb. load, whereas only the men showed significant change for a 26-lb. load.

Adult↗
PubMed2024

Acute strength exercise training impacts differently the HERV-W expression and inflammatory biomarkers in resistance exercise training individuals.

BACKGROUND: Human Endogenous Retroviruses (HERVs) are fossil viruses that composes 8% of the human genome and plays several important roles in human physiology, including muscle repair/myogenesis. It is believed that inflammation may also regulate HERV expression, and therefore may contribute in the muscle repair, especially after training exercise. Hence, this study aimed to assess the level of HERVs expression and inflammation profile in practitioners' resistance exercises after an acute strength training session. METHODS: Healthy volunteers were separated in regular practitioners of resistance exercise training group (REG, n = 27) and non-trained individuals (Control Group, n = 20). All individuals performed a strength exercise section. Blood samples were collected before the exercise (T0) and 45 minutes after the training session (T1). HERV-K (HML1-10) and W were relatively quantified, cytokine concentration and circulating microparticles were assessed. RESULTS: REG presented higher level of HERV-W expression (~2.5 fold change) than CG at T1 (p<0.01). No difference was observed in the levels of HERV-K expression between the groups as well as the time points. Higher serum TNF-&#x3b1; and IL-10 levels were verified post-training session in REG and CG (p<0.01), and in REG was found a positive correlation between the levels of TNF-&#x3b1; at T1 and IL-10 at T0 (p = 0.01). Finally, a lower endothelial microparticle percentage was observed in REG at T1 than in T0 (p = 0.04). CONCLUSION: REG individuals exhibited a significant upregulation of HERV-W and modulation of inflammatory markers when compared to CG. This combined effect could potentially support the process of skeletal muscle repair in the exercised individuals.

Humans↗
PubMed2026

Comparing the Effects of Push and Hold Isometric Training on Strength and Musculotendinous Adaptations: A Within-Subject Randomized Controlled Trial.

Lum, D, Oranchuk, DJ, Chen, SE, and Kong, PW. Comparing the effects of push and hold isometric training on strength and musculotendinous adaptations: A within-subject randomized controlled trial. J Strength Cond Res 40(9): 1050-1058, 2026-Despite recent interest in delineating pushing (PIMA) and holding (HIMA) isometric muscle actions, training-induced adaptations have not been examined. As such, we compared the strength and morphological adaptations between PIMA and HIMA training. Twenty limbs across 10 adults (5 men, 5 women, age: 31.4 &#xb1; 6.5 years) were randomly assigned to PIMA or HIMA conditions and underwent 12 training sessions over 6 weeks. PIMA required subjects to exert force against a fixed lever while the HIMA limb maintained a set joint angle while resisting an isotonic lever. During each contraction, subjects had to exert force at 70% of maximal voluntary contraction for 20 seconds at an 80&#xb0; knee angle, for 4-6 repetitions. Subjects completed isometric, concentric, and eccentric knee extension assessments for both limbs before and after the intervention. Pre- and postintervention ultrasound scans were performed to determine quadriceps muscle architecture and patellar tendon thickness. Increased isometric torque was found following both conditions (p < 0.05, g = 0.30-0.36), while concentric (p < 0.05, g = 0.31) and eccentric (p < 0.01, g = 0.50) torque only increased following PIMA. Both conditions increased muscle thickness (p < 0.05, g = 0.27-0.88) and vastus lateralis fascicle length (p < 0.05, g = 0.20-0.31). Only HIMA increased patellar tendon thickness (p < 0.05, g = 0.12). The increase in total quadriceps (p < 0.05, g = 0.46) and especially rectus femoris (p < 0.05, g = 1.44) thickness was greater in HIMA. The results suggest that PIMA may be more effective at improving strength, while HIMA may be superior for inducing morphological adaptations. Larger sample sizes and more ecologically valid training programs are warranted to further elucidate potential differences between different isometric types.

Humans↗
PubMed1975

Enzyme activities and muscle strength after "sprint training" in man.

Sprint type strength training was performed 3-4 times a week for 8 weeks by 4 healthy male students (16-18 yrs). The training was carried out on a treadmill at high speed and with high inclination. Muscle biopsies were obtained from vastus lateralis before and after the training period for histochemical classification of slow and fast twitch muscle fibres and for biochemical determination of metabolites and enzyme activities. Muscle fibre type distribution was unchanged, whereas fibre area indicated an increase for both fibre types in 3 subjects after training. The muscle enzyme activities of Mg2+ stimulated ATPase, myokinase and creatine phosphokinase increased 30, 20, and 36 percent, respectively. Muscle concentration of ATP and creatine phosphate (CP) did not change with training. Sargent's jump increased with on average 4 cm (from 47 to 51 cm), maximal voluntary contraction (MVC) with 19 kp (from 165 to 184 kp), and endurance at 50 percent of MVC with 9 s (from 47 to 56 s), respectively. After training all subjects showed a gain in body weight (mean 1.4 kg) and in thigh circumference (mean 1.5 cm) indicating a larger leg muscle volume and consequently also an increase in total ATP and CP.

Actomyosin↗
PubMed1978

The effect of circuit weight training on strength, cardiorespiratory function, and body composition of adult men.

The purpose of this study was to determine the changes elicited by circuit weight training (CWT) and running (RN) programs conducted 3 days/week for 20 weeks. Subjects were randomly assigned to one of three groups: CWT (n = 11); RN (n = 16); and control (n = 14). CWT consisted of 10 exercises performed in 2 sets of 15 reps with 20 to 25 sec rest between exercises. CWT workout time decreased from 30 min to 23 min; exercise heart rate (HR) increased from 79% to 84% max; average weight increased from 42% to 56% of max 1 RM strength and total weight increased 81% (1506 to 2720 lbs/workout). The RN group exercised at 85% max HR for 23 to 27 min/workout. Multivariate and step-down analyses showed the CWT group to be significantly different from the control group at the end of 20 weeks in leg press strength, fat weight, and Vo2 max (1/min). The RN group was significantly different from the CWT group in Vo2 max and treadmill time. Univariate analyses revealed no differences between the CWT and control groups in Vo2 max expressed as ml/kg LBW.min but did show a significant superiority of the RN group over the other two groups in this variable. It was concluded that the CWT program was most specific in improving strength and changing body composition and produced only a small aerobic effect as measured on the treadmill running test.

Adult↗