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PubMed1994

Serum hormones and strength development during strength training in middle-aged and elderly males and females.

Effects of a 12-week progressive strength training period on serum concentrations of testosterone, cortisol and sex-hormone-binding globulin (SHBG) as well as on strength development of the leg extensor muscles were investigated in nine middle-aged males (M50; range 44-57 years) and in nine middle-aged females (F50; range 43-54 years) as well as in 10 elderly males (M70; range 64-73 years) and in 11 elderly females (F70; range 66-73 years). Substantial increases took place in maximal isometric strength during the 12-week training period both in M50 (from 2834 +/- 452 to 3941 +/- 772 N; P < 0.001) and in F50 (from 2627 +/- 725 to 3488 +/- 1017 N; P < 0.001) as well as in M70 (from 2591 +/- 736 to 3075 +/- 845 N; P < 0.01) and in F70 (from 1816 +/- 427 to 2483 +/- 408 N; P < 0.001). The relative increases in strength during the 12-week training period did not differ significantly between the groups. However, during the last 4 weeks of the training none of the groups demonstrated further increases in strength but it actually decreased in F50 (P < 0.05), M70 (P < 0.01) and in F70 (P < 0.05). No systematic changes were observed during the training in the mean concentrations of serum total testosterone, free testosterone, cortisol, and SHBG, nor in testosterone/cortisol and testosterone/SHBG ratios. However, the individual levels of serum testosterone and testosterone/cortisol ratio and the individual changes in strength during the last four most intensive training weeks of the 12-week period were in significant positive linear correlation in F70 (r = 0.57; P < 0.05) and in M70 (r = 0.61; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2005

Muscle strength response to strength training is influenced by insulin-like growth factor 1 genotype in older adults.

Strength training (ST) is considered an intervention of choice for the prevention and treatment of sarcopenia. Reports in the literature have suggested that the insulin-like growth factor I protein (IGF-I) plays a major role in ST-induced skeletal muscle hypertrophy and strength improvements. A microsatellite repeat in the promoter region of the IGF1 gene has been associated with IGF-I blood levels and phenotypes related to IGF-I in adult men and women. To examine the influence of this polymorphism on muscle hypertrophic and strength responses to ST, we studied 67 Caucasian men and women before and after a 10-wk single-leg knee-extension ST program. One repetition maximum strength, muscle volume via computed tomography, and muscle quality were assessed at baseline and after 10 wk of training. The IGF1 repeat promoter polymorphism and three single-nucleotide polymorphisms were genotyped. For the promoter polymorphism, subjects were grouped as homozygous for the 192 allele, heterozygous, or noncarriers of the 192 allele. After 10 wk of training, 1-repetition maximum, muscle volume, and muscle quality increased significantly for all groups combined (P < 0.001). However, carriers of the 192 allele gained significantly more strength with ST than noncarriers of the 192 allele (P = 0.02). There was also a nonsignificant trend for a greater increase in muscle volume in 192 carriers than noncarriers (P = 0.08). No significant associations were observed for the other polymorphisms studied. Thus these data suggest that the IGF1 promoter polymorphism may influence the strength response to ST. Larger sample sizes should be used in future studies to verify these results.

Aged↗

PubMedDate not supplied

Change in self-efficacy following a single strength training session predicts sedentary older adults' subsequent motivation to join a strength training program.

PURPOSE: To determine whether performance accomplishment and perceived exertion predict change in self-efficacy following a single strength training session and whether change in self-efficacy predicts subsequent motivation to join a strength training program. METHODS: Fifty-nine sedentary older adults participated in a single strength training session at a seniors' exercise center, completed measures of perceived exertion and self-efficacy, and received a voucher for a free fitness consultation. RESULTS: Regression analyses indicated that perceived exertion predicted change in self-efficacy. In turn, greater change in self-efficacy was associated with a greater likelihood of using the voucher for a fitness consultation. DISCUSSION: Sedentary older adults can be motivated toward joining a strength training program after an initial strength training session that required low exertion. Practitioners could increase strength training initiation by providing such experiences.

Aged↗

PubMed1976

Studies on muscular strength-myogram (MSMG). Part 1. A new device of apparatus for measuring muscular strength-myogram.

1. A new apparatus, consisting of a strain gauge and a carrier amplifier, was devised for measuring back muscular and shoulder arms strength by the author. This apparatus was applied for analysing myogenic disorder related to muscular fatigue or pain. 2. Muscular strength with load and its myogram were recorded simultaneously, and their changes during the exertion were analysed. 3. Muscular strength-myograms of sternocleidomastoid muscle, upper trapezius muscle, deltoid muscle, rhomboid muscle and lumbodorsal muscle were observed from the back muscular strength-myogram, and those of teres minor muscle and major pectoral muscle from the shoulder arm strength-myogram. 4. It seemed paradoxically that the amplitude of action myogram increased in proportion to the grade of lowering of muscular strength caused by muscular fatigue or pain.

Adult↗

PubMed2003

Antiandrogens in hormonal contraception limit muscle strength gain in strength training: comparison study.

AIM: To determine antiandrogen effects on muscle strength gain and fat-free mass increase during exercise in women using hormonal contraception with antiandrogen content. METHODS: The study included 50 women (age range, 18-30 years; mean-/+SD, 26-/+3) using hormonal contraception for at least 12 months before the beginning of the study. They were divided into two groups: "antiandrogen" group (n=26) and "estrogen-progestogen" group (n=24) groups. The subjects participated in strength training sessions 3 times a week during 16 weeks. Initially, there were no differences between the groups in fat-free mass, muscle strength, or maximum oxygen uptake. The parameters were measured before, during, and after the training period. RESULTS: After the training period, the mean increase of fat-free mass was significantly greater in the estrogen-progestogen group (p<0.001). The mean gain in the muscle strength (in Newtons) was also more evident in estrogen-progestogen group (1289.0-/+17.1 N vs 101.9-/+18.5 N; p<0.001). There were no differences in the maximum oxygen consumption (VO(2)max). CONCLUSION: Antiandrogens had a negative effect on muscle strength, minimizing the effects of strength training in women. Hormonal contraception containing antiandrogens should be avoided in young exercising women.

Adolescent↗

PubMed1991

Effects of simultaneous training for strength and endurance on upper and lower body strength and running performance.

This study examined simultaneous training for strength and endurance during a 13-week, 3-day a week program of hydraulic resistive circuit training and running. Eighteen college males (U.S. Army ROTC) were placed into low resistance (LR; n = 10) or high resistance (HR; n = 8) groups, and 10 college males were controls and did not train. There were 20 exercise stations (7 upper and lower body, and 6 supplementary). LR and HR performed 2 circuits with a work/rest ratio of 20 to 40 s during the 40 min workout. LR trained at two low resistances (approximately 100 cm.s-1), while HR trained at a higher resistance (approximately 50 cm.s-1). Following the workout, subjects ran 2 miles. Pre and post tests included strength, physical fitness, and anthropometry. Strength was assessed with (1) hydraulic resistance dynamometry for 4 exercises at 2 speeds using a computerized dynamometer (Hydra-Fitness, Belton, TX); (2) isokinetic and isotonic upright squat and supine bench press using the Ariel Exerciser (Trabuco Canyon, CA); (3) concentric and eccentric arm flexion/extension at 60 and 120 degrees.s-1 on the Biodex dynamometer (Shirley, NY), and (4) 1-RM free weight concentric and eccentric arm flexion and extension. The fitness tests included 2-mile run, sit-ups, and push-ups. Anthropometry included 3 fatfolds, 6 girths, and arm and leg volume. There were no significant changes in body composition or interactions between the fitness test measures and the 2 training groups (p greater than 0.05). Improvements averaged 15% (run time), 30% (push-ups), and 19% (sit-ups; p less than 0.05). Significant improvements also occurred in 3 of 8 measures for hydraulic testing (overall change 8.8%), in 3 of 4 1-RM tests (9.4%), and in 2 of 8 Biodex tests (6%), but no significant changes for isokinetic and isotonic squat and bench press (1.9%). The change in overall strength averaged 6.5% compared to 16% in a prior study that used hydraulic resistive training without concomitant running. We conclude that gains in strength were somewhat compromised by the simultaneous run training, and that improvements in strength and run performance were independent of LR and HR training intensity.

Adult↗

PubMed1984

Reliability of isometric strength testing. Temporal factors and strength variation.

Isometric strength measurements of grip, pronation, supination, and elbow extension and flexion on dominant and nondominant sides were made on 40 normal subjects (age range, 40-70 years) to investigate the variability of isometric strength at different times of the day. Statistically significant differences were found in certain pronation, supination, and grip comparisons. No statistically significant difference was found in extension and flexion. Although significant, the absolute change in strength at different times of the day was small and showed no consistent trend. On the basis of these data, it appears that this variation can probably not be routinely detected in the normal clinical setting. However, the study further defines the reliability of isometric strength testing and should be considered in further attempts at more accurate measurement of elbow function. The small variations of strength, approximately 5%, that can be measured universally with sensitive testing equipment, are clinically relevant. However, when attempting to determine an impairment state in order not to place too much importance on small differences, care should be exercised in interpreting strength measurements. This investigation demonstrates how the application of sophisticated biomechanical techniques may be employed to provide useful objective information in the difficult clinical area of disability assessment. Disability judgments may be made more accurate as more is learned of the normal variables influencing objective measurement.

Adult↗

PubMed1974

A study of the influence during trituration of air-borne impurities on the strength of amalgam.

The purpose of this study was to determined the effect of air-borne gaseous impurities, introduced during trituration, on the strength of amalgams. Four experiments were conducted. Each experiment consisted of a control group (1) in which the amalgam was triturated in air and an experimental group (2) in which the amalgam was triturated in argon, an inert gas. Standard specimens yielded mean diametral tensile strengths of 5950 psi (1) and 6603 psi (2). Hand compacted specimens yielded mean diametral tensile strengths of 5829 psi (1) and 6412 psi (2). Standard specimens yielded mean compacted hydraulically yielded mean uniaxial tensile strengths of 10,928 psi (1) and 11,660 psi (2). Statistically, the differences between the means for each experiment are significant. Hence, trituration in an inert gas has been shown to be an effective method for increasing the strength of amalgam.

Air Pollution↗

PubMed2003

pQCT bone strength index may serve as a better predictor than bone mineral density for long bone breaking strength.

Bone mineral density (BMD) is commonly used to predict osteoporotic fracture risk without considering the geometry of the bone. However, geometric parameters are also important in determination of bone strength. An index including both material and geometric properties may be therefore more relevant in prediction of fracture risk. We studied the correlation between parameters measured by noninvasive peripheral quantitative computed tomography (pQCT) and bone bending strength of the diaphysis of 45 fresh goat humeri and 27 femora. Multislice pQCT was used for measuring volumetric diaphyseal cortical BMD, total BMD, diaphyseal and cortical cross-sectional area (CSA), and cross-sectional moment of inertia (CSMI) and their derived bone strength indices (BSIs), including BSI(CSMI) (cortical BMD x CSMI) and BSI(CSA) (cortical BMD x cortical CSA). Conventional dual-energy absorptiometry (DXA) was also conducted to measure areal BMD of diaphysis for comparison. Ultimate fracture load was obtained via three-point bending test. Results showed that for femora, fracture load was correlated better with BSI(CSA) ( r = 0.697, P < 0.001) than cortical BMD ( r = 0.304, P > 0.05) and total BMD ( r = 0.387, P > 0.05) measured using pQCT and areal BMD ( r = 0.612, P < 0.001) measured using DXA. For humeri, fracture load was also correlated with BSI(CSA) ( r = 0.579, P < 0.001) but not with other pQCT parameters including cortical BMD and total BMD ( r = 0.282 and 0.305, respectively; P > 0.05, both). The best correlation was found with areal BMD measured by DXA ( r = 0.760, P < 0.001). In conclusion, pQCT noninvasive BSI(CSA) derived from cortical BMD (material) and its cortical CSA (bone geometry or distribution) may serve as an important noninvasive index for predicting long bone bending strength. The bending strength was also predicted by bone mass (areal BMD) measured by DXA, an integration of bone mineral and geometry. Further clinical studies are needed to validate the predictive value of BSI in long bone osteoporotic fracture.

Animals↗

PubMed1996

Strength gains without muscle injury after strength training in patients with postpolio muscular atrophy.

We evaluated changes in the dynamic and isometric strength in the newly weakened quadriceps muscles and asymptomatic triceps muscles of 6 patients with postpolio muscular atrophy (PPMA) after 10 weeks of progressive resistance strength training. Alterations in muscle size were determined with magnetic resonance imaging. Serum creatine kinase levels were measured throughout training, and histological signs of muscle injury and changes in muscle fiber size and types were assessed with muscle biopsies before and after training. Exercise training led to an increase in dynamic strength of 41% and 61% for the two knee extensor tests, and 54% and 71% for the two elbow extensor tests. Up to 20% of the improvement was maintained 5 months after cessation of training. Isometric strength, whole muscle cross-sectional areas of quadriceps and triceps muscles, and serum muscle enzymes did not change. No destructive histopathological changes were noted in the repeat muscle biopsies, and no consistent changes in muscle fiber size or fiber type percentages were observed. These results demonstrate that a supervised resistance training program can lead to significant gains in dynamic strength of both symptomatic and asymptomatic muscles of PPMA patients without serological or histological evidence of muscular damage.

Biopsy↗

PubMed2002

The effects of progressive strength training and aerobic exercise on muscle strength and cardiovascular fitness in women with fibromyalgia: a pilot study.

OBJECTIVE: To determine the safety, feasibility and consequences of a program of progressive strength training and cardiovascular exercise in women with fibromyalgia syndrome (FMS). METHODS: Fifteen women with confirmed FMS were monitored for injury and exercise compliance, and assessed for muscle strength (1-repetition maximum technique), cardiovascular endurance (6-minute walk test), and functional status (Fibromyalgia Impact Questionnaire [FIQ]) before and after a 20-week exercise intervention. RESULTS: Zero injuries and an 81% compliance rate occurred during training. Improvement was seen in muscle strength of the lower (191 +/- 75 to 265 +/- 67 pounds; P < 0.001) and upper (61 +/- 18 to 76 +/- 18 pounds; P < 0.001) body, 6-minute walk distance (530 +/- 80 to 629 +/- 74 meters; P < 0.001), and in FIQ score (44 +/- 9 to 32 +/- 14; P < 0.01). CONCLUSION: A program of progressive strength training and cardiovascular exercise can be safe, well tolerated, and effective at improving muscle strength, cardiovascular endurance and functional status in women with FMS without exacerbating symptoms. This program may also contribute to a reduction in the severity of several symptoms.

Adult↗

PubMed2000

Neuromuscular adaptation during prolonged strength training, detraining and re-strength-training in middle-aged and elderly people.

Effects of a 24-week strength training performed twice weekly (24 ST) (combined with explosive exercises) followed by either a 3-week detraining (3 DT) and a 21-week re-strength-training (21 RST) (experiment A) or by a 24-week detraining (24 DT) (experiment B) on neural activation of the agonist and antagonist leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris, maximal isometric and one repetition maximum (1-RM) strength and jumping (J) and walking (W) performances were examined. A group of middle-aged (M, 37-44 years, n = 12) and elderly (E, 62-77, n = 10) and another group of M (35-45, n = 7) and E (63-78, n = 7) served as subjects. In experiment A, the 1-RM increased substantially during 24 ST in M (27%, P<0.001) and E (29%, P<0.001) and in experiment B in M (29%, P<0.001) and E (23%, P<0.01). During 21 RST the 1-RM was increased by 5% at week 48 (P<0.01) in M and 3% at week 41 in E (n.s., but P<0.05 at week 34). In experiment A the integrated electromyogram (IEMG) of the vastus muscles in the 1-RM increased during 24 ST in both M (P<0.05) and E (P<0.001) and during 21 RST in M for the right (P<0.05) and in E for both legs (P<0.05). The biceps femoris co-activation during the 1-RM leg extension decreased during the first 8-week training in M (from 29+/-5% to 25+/-3%, n.s.) and especially in E (from 41+/-11% to 32+/-9%, P<0.05). The CSA increased by 7% in M (P<0.05) and by 7% in E (P<0.001), and by 7% (n.s.) in M and by 3% in E (n.s.) during 24 ST periods. Increases of 18% (P<0.001) and 12% (P<0.05) in M and 22% (P<0.001) and 26% (P<0.05) in E occurred in J. W speed increased (P<0.05) in both age groups. The only decrease during 3 DT was in maximal isometric force in M by 6% (P<0.05) and by 4% (n.s.) in E. During 24 DT the CSA decreased in both age groups (P<0.01), the 1-RM decreased by 6% (P<0.05) in M and by 4% (P<0.05) in E and isometric force by 12% (P<0.001) in M and by 9% (P<0.05) in E, respectively, while J and W remained unaltered. The strength gains were accompanied by increased maximal voluntary neural activation of the agonists in both age groups with reduced antagonist co-activation in the elderly during the initial training phases. Neural adaptation seemed to play a greater role than muscle hypertrophy. Short-term detraining led to only minor changes, while prolonged detraining resulted in muscle atrophy and decreased voluntary strength, but explosive jumping and walking actions in both age groups appeared to remain elevated for quite a long time by compensatory types of physical activities when performed on a regular basis.

Adaptation, Physiological↗

PubMed1995

Concentric and eccentric strength of trunk muscles: influence of test postures on strength and characteristics of patients with chronic low-back pain.

The purpose of this study was to determine the influence of test postures on trunk muscle strength, and to clarify the difference between concentric and eccentric strength of healthy subjects and patients with chronic low-back pain (CLBP). Volunteered and controlled trials took place at a university hospital, which is a referral center and is also open to the general community. The patients were selected from the outpatient care in the university hospital. Fifty healthy subjects (25 men and 25 women; average age 25.7 years, ranging from 23 to 34 years) and 48 patients with CLBP (26 men and 22 women; average age 33.5 years, ranging from 26 to 39 years) volunteered for this study. The main outcome measures were flexor and extensor peak torque/body weight, and flexor/extensor peak torque ratio during concentric and eccentric contractions; Eccentric/concentric peak torque ratio in flexor and extensor. Trunk-muscle strength was significantly greater in the sitting posture when measured with the subjects' feet against the floor (p < .05). Some patients complained of a slight low-back pain during testing, although the pain was not aggravated in any patients. In both concentric and eccentric contraction modes, the patients with CLBP had greater flexor/extensor ratios than the healthy subjects (p < .01). This implies that extensors are more affected in these patients. However, a great imbalance between concentric and eccentric strength of the patients was found, not only in extensors, but also in flexors (p < .01). The current study shows that one should consider the test posture carefully when measuring trunk-muscle strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1998

Self-directed strength training: its effect on leg strength in men with mental retardation.

OBJECTIVE: To compare isokinetic measures of peak torque (newton-meters) and total work (joules) in men with mental retardation on a test of knee extension after 12 weeks of trainer-directed training and 1 year of self-directed training. DESIGN: Repeated measures of analysis of variance using a planned comparison approach involving an independent 2 x 3 (group x test) design. SETTING: Subjects were tested at a university athletic training facility on three separate days. SUBJECTS: Volunteer sample of 12 subjects with mental retardation: 6 in strength training group, 6 in control group. INTERVENTION: Subjects performed an isokinetic knee extension test at a velocity of 60 degrees/sec on three separate days. Test 1 was the pretest, test 2 was conducted after 12 weeks of trainer-directed hydraulic resistance training, and test 3 was conducted after 1 year of self-directed hydraulic resistance training. RESULTS: For both isokinetic parameters measured, the strength-trained subjects demonstrated significantly higher scores after 12 weeks of training and after 1 year of training than the scores achieved on the pretest. No significant differences in peak torque or total work scores were found between test 2 and test 3 scores for the strength-trained group. No significant changes in isokinetic scores between test sessions were found for the control subjects. CONCLUSION: Men with mental retardation can maintain strength following a self-directed hydraulic resistance strength training program.

Adult↗

PubMed1992

Strength and bite, Part 2: Testing isometric strength using a MORA set to a functional criterion.

The effect on isometric strength of biting on three intraoral devices and habitual occlusion was analyzed. Only subjects who showed a relative weakness to the Isometric Deltoid Press (IDP) when biting as opposed to maintaining the mandible in an unsupported rest position were included in the study. Both in the original 35 subjects and the 23 subjects returning on the second day, performance wearing the appliance set by a functional criterion of peak strength (locking) to the IDP was significantly greater than wearing a placebo appliance and a bite raising appliance that deflected the mandible 1 mm to the left. Strength biting on the appliance set by a functional criterion was significantly greater than all these conditions. Strength biting in habitual trials that were matched with the deflection condition was found to be significantly greater than that biting in the placebo condition. It was concluded that a relationship does exist between bite and isometric strength. Previous speculation about the role of placebo effect was not substantiated by the data gathered in this experiment.

Adolescent↗

PubMed1951

On the relation of the strength-frequency curve in excitation by alternating current to the strength-duration and latent addition curves of the nerve fiber.

1. Determinations were done of the strength-duration, the strength-frequency, and the latent addition curves with single fiber preparations. 2. Calculation of the strength-duration and strength-frequency curves from the latent addition data by the Blair-Monnier-Hill-Rashevsky theory yielded results which showed a considerable divergence from the actual data. Calculation by the method of integrating the whole latent addition curve yielded satisfactory results. 3. The effects of electrotonus and the inactive tissues around the nerve fiber upon the strength-frequency relation were investigated. 4. It was suggested that, for alternating current stimuli and two-way condenser discharge stimuli of very high frequencies, threshold was lowered by the rectifying action of the plasma membrane.

Nerve Fibers↗

PubMedDate not supplied

High intensity strength training improves strength and functional performance after stroke.

OBJECTIVE: To evaluate the effects of a progressive resistance strength training program on changes in muscle strength, gait, and balance in older individuals 1 yr after stroke, seven individuals were recruited who were greater than 60-yr-old, 1 yr after stroke, living at home, and able to follow verbal commands. DESIGN: Subjects participated in a 12-wk 2x per wk resistance training program at 70% of 1 repetition maximum. RESULTS: Lower limb strength improved 68% on the affected side and 48% on the intact side during training, with the largest increases observed for hip extension (affected side: 88%, P < 0.01; intact side: 103%, P < 0.001). Repeated chair stand time decreased 21% (P < 0.02). Motor performance assessed by the Motor Assessment Scale improved 9% (P < 0.04) and static and dynamic balance (Berg balance scale) improved 12% (P < 0.004). Progressive resistance training in individuals 1 yr after stroke improves affected and intact side lower limb strength and was associated with gains in chair stand time, balance, and motor performance. CONCLUSIONS: These results support the concept that strength training is an appropriate intervention to improve the quality of physical function in older community dwelling stroke survivors.

Activities of Daily Living↗

PubMed1984

Muscle strength and cross-sectional area in man: a comparison of strength-trained and untrained subjects.

This study has examined muscle strength and cross-sectional area in a group of 35 healthy untrained male subjects and 8 subjects who had been engaged in a strenuous weight-training programme. The maximum voluntary knee extension force which could be produced by the untrained subjects was 742 +/- 100 N (mean +/- SD). The trained subjects could produce a significantly (p less than 0.001) greater force (992 +/- 162 N). Cross-sectional area of the knee-extensor muscle group was 81.6 +/- 11.8 cm2 in the untrained subjects and 104.1 +/- 12.3 cm2 in the trained subjects (p less than 0.001). In the untrained subjects, a significant correlation existed between strength and muscle cross-sectional area (r = 0.56, p less than 0.001). In the same group of subjects, there was a significant inverse relationship between muscle cross-sectional area and the ratio of strength to cross-sectional area (r = 0.55, p less than 0.001). The mean ratio of strength to cross-sectional area was 9.20 +/- 1.29 for the untrained group whereas for the trained group this ratio was 9.53 +/- 1.01. It is suggested that the inverse relationship between strength per unit cross-sectional area and cross-sectional area results in part from an increased angle of pennation in the larger muscles.

Adult↗