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PubMed2001

Effects of regular and slow speed resistance training on muscle strength.

BACKGROUND: The study assessed a way to increase the intensity and effectiveness of resistance training by comparing training with a slower repetition speed to training with a conventional repetition speed. Slower repetition speed may effectively increase intensity throughout the lifting phase while decreasing momentum. METHODS: Two studies were done with untrained men (N=65) and women (N=82), (mean age=53.6) who trained two to three times per week for eight to 10 weeks on a 13 exercise Nautilus circuit performing one set of each exercise. Participants exclusively trained using regular speed repetitions for 8 to 12 repetitions per set at 7 sec each (2 sec lifting, 1 sec pause, 4 sec lowering) or a Super Slow training protocol where they completed 4 to 6 repetitions per set at 14 sec each (10 sec lifting, 4 sec lowering). All of the participants were tested for either the 10 repetition-maximum (RM) weightload (regular-speed group) or the 5-RM weightload (slow-speed group). RESULTS: In both studies, Super-Slow training resulted in about a 50% greater increase (p<0.001) in strength for both men and women than regular speed training. In Study 1, the Super-Slow training group showed a mean increase of 12.0 kg and the regular speed group showed an increase of 8.0 kg increase (p<0.001). In Study 2, the Super-Slow training group showed a 10.9 kg increase and the regular speed group showed an increase of 7.1 kg (p<0.001). CONCLUSIONS: Super-Slow training is an effective method for middle-aged and older adults to increase strength. Although studies still need to be done with at-risk populations, repetition speed should be considered when prescribing resistance training.

Adult↗
PubMedDate not supplied

Creatine and beta-hydroxy-beta-methylbutyrate (HMB) additively increase lean body mass and muscle strength during a weight-training program.

We investigated whether creatine (CR) and beta-hydroxy-beta-methylbutyrate (HMB) act by similar or different mechanisms to increase lean body mass (LBM) and strength in humans undergoing progressive resistance-exercise training. In this double-blind, 3-wk study, subjects (n = 40) were randomized to placebo (PL; n = 10), CR (20.0 g of CR/d for 7 d followed by 10.0 g of CR/d for 14 d; n = 11), HMB (3.0 g of HMB/d; n = 9), or CR-and-HMB (CR/HMB; n = 10) treatment groups. Over 3 wk, all subjects gained LBM, which was assessed by bioelectrical impedance analysis. The CR, HMB and CR/HMB groups gained 0.92, 0.39, and 1.54 kg of LBM, respectively, over the placebo group, with a significant effect with CR supplementation (main effect P = 0.05) and a trend with HMB supplementation (main effect P = 0.08). These effects were additive because there was no interaction between CR and HMB (CR x HMB main effect P = 0.73). Across all exercises, HMB, CR, and CR/HMB supplementation caused accumulative strength increases of 37.5, 39.1, and 51.9 kg, respectively, above the placebo group. The exercise-induced rise in serum creatine phosphokinase was markedly suppressed with HMB supplementation (main effect P = 0.01). However, CR supplementation antagonized the HMB effects on serum creatine phosphokinase (CR x HMB interactive effect P = 0.04). Urine urea nitrogen and plasma urea were not affected by CR supplementation, but both decreased with HMB supplementation (HMB effect P < 0.05), suggesting a nitrogen-sparing effect. In summary, CR and HMB can increase LBM and strength, and the effects are additive. Although not definitive, these results suggest that CR and HMB act by different mechanisms.

Adult↗
PubMed2001

Relationship between muscle strength and the time taken to complete a standardized walk-turn-walk test.

We examined the effects of age and gender on the relationship between knee strength and walking time during a walk-turn-walk test in 176 male and 168 female generally healthy participants of the Baltimore Longitudinal Study of Aging who were aged 21-89 years. Subjects were timed as they walked 50 ft (15.24 m), turned around, and walked back to the starting point, both at a comfortable pace and as fast as possible. Isokinetic concentric knee extensor strength was measured at 30 degrees /s by using a Kin-Com dynamometer. Both comfortable and fast gait times increased with increasing age for both women and men, starting in middle age. An interaction was found between gender and age showing that older women are slower than older men at both paces. Gait time decreased linearly with increasing knee extensor strength, plateauing at higher strength levels (>130 N m for comfortable gait, and 190 N m for fast gait). Most women occupied the linear part of the curve below the plateau. Adjustment for body size, age, physical activity, and particularly number of steps to complete the task removed the relationship between strength and gait time for the comfortable gait. Women took longer to complete the walk-turn-walk test than men at older ages, were on the linear part of the strength-gait time relationship, and used more steps to complete the task, all of which may contribute to their greater likelihood of frailty in later years.

Adult↗
PubMed1989

The relationship between muscle strength and sprint kinematics in elite sprinters.

Twenty-three elite sprinters, 9 females and 14 males, were filmed while performing a maximal sprint. Age, height, weight, and personal best 100 m time were also determined for each sprinter. Several kinematic variables were calculated for each athlete from the filmed sprint, including stride length, stride frequency, horizontal and vertical velocity of the CG, and the angular kinematics of the limbs. A Kin/Com isokinetic dynamometer was used to determine lower limb peak and average torque values. Correlation coefficients were calculated between each of the kinematic variables and each of the strength variables. Stepwise multiple regression analysis was also carried out for each set of kinematic and strength variables, to determine the best predictors of sprinting speed. Significant relationships were noted between sprinting times for the 100 m and peak torque scores (N.m/kg) for males for fast concentric knee extension and slow eccentric dorsiflexion, and for females for concentric dorsiflexion at both speeds, and slow eccentric dorsiflexion.

Adolescent↗
PubMed1997

Gait analysis, isokinetic muscle strength measurement in patients with Parkinson's disease.

The aim of this study was to describe motor performance in Parkinson patients in relation to controls. Gait, concentric isometric and eccentric strength in the ankle dorsiflexors were investigated in 25 patients with Parkinson's disease and in 37 control subjects of the same age. In patients concentric torque was significantly lowered but, eccentric torque was significantly lowered in male patients only. Among controls a significant difference in strength was found between sexes. This was not found in the patient group. No correlation between strength tests and clinical ratings was found in the patient group. Patients walked with significantly lower maximum and ordinary velocity, compared with controls. At constant velocity, stride length was shorter, single support had a shorter duration. The duration for heel on to ball on in males was shorter, reflecting the flat foot strike of Parkinson patients. Single support and the duration of heel on to ball on correlated significantly to the clinical ratings in male but not in female patients. In the male group of patients there was a relation between concentric strength on the one hand and gait velocity, stride length and stride frequency on the other. Female patients generally had fewer symptoms and less deviation from their respective controls in the measurements. The comparatively simple neurophysiological tests presented here may be suitable for evaluation of patients with Parkinson's disease.

Aged↗
PubMed2005

Reconstructed hip joint position and abductor muscle strength after total hip arthroplasty.

We evaluated 60 limbs in 30 patients with unilateral primary total hip arthroplasty and nondiseased contralateral hip. The ratio of femoral offset (FO) to the body weight lever arm (FO ratio) and the ratio of the height of hip center (HC) to pelvic height (HC ratio) were calculated on radiographs. Isometric hip abductor strength was measured by dynamometer. The ratio of normalized strength of the reconstructed side to that of the nonoperated side was calculated (strength ratio). The FO ratio correlated positively to the strength ratio (r = 0.491; P = .0059), whereas the HC ratio correlated negatively (r = -0.568; P = .0011). Slight increase of FO ratio along with restoration of normal hip joint center erring on the side of slight inferomedial cup positioning appeared to optimize hip abductor function.

Aged↗
PubMed1992

Muscle strength is improved after parathyroidectomy in patients with primary hyperparathyroidism.

Fatigue and muscular weakness are prevalent symptoms in patients with primary hyperparathyroidism. This study examined muscular strength before and after operation in a group of eight patients with hyperparathyroidism and in a control group of seven patients with benign thyroid lesions. The maximum power grip, pronation and supination, and endurance for the same muscular movements, were studied by means of a computer program. Patients with hyperparathyroidism had impaired muscular strength compared with the controls but 12 months after operation a significant improvement of all muscular performance was observed. No such improvement was detectable among the controls. There was no correlation between the levels of serum calcium and parathyroid hormone and the measurements recorded before and after operation. Muscular impairment in hyperparathyroidism is measurable by an objective technique. Improvement occurs after surgery.

Adult↗
PubMedDate not supplied

What best protects the inverted weightbearing ankle against further inversion? Evertor muscle strength compares favorably with shoe height, athletic tape, and three orthoses.

We measured the maximal isometric eversion moment developed under full weightbearing in 20 healthy adult men (age, 24.4 +/- 3.4 years; mean +/- SD) with their ankles in 15 degrees of inversion. Tests were performed at both 0 degree and 32 degrees of ankle plantar flexion in low- and in three-quarter-top shoes with and without adhesive athletic tape or one of three proprietary ankle orthoses. At 0 degree of ankle plantar flexion, the mean maximal voluntary resistance of the unprotected ankle to an inversion moment was 50 +/- 8 N-m; this increased by an average of 12% (or 6 N-m) when the subject wore a three-quarter-top basketball shoe. The maximal voluntary resistances to inversion moments developed with the ankles further protected by athletic tape or any of three orthoses were not significantly different. Biomechanical calculations suggest that at 15 degrees of inversion the fully active ankle evertor muscles isometrically developed a moment up to six times larger than that developed when an athlete wears a three-quarter-top shoe alone and more than three times larger than that developed passively when the athlete has tape or an orthosis worn inside a three-quarter-top shoe. We conclude that fully activated and strong ankle evertor muscles are the best protection for a near-maximally inverted ankle at footstrike.

Adult↗
PubMed1986

Lung function and respiratory muscle strength after propranolol in thyrotoxicosis.

Thirty-five thyrotoxic patients were assessed before treatment, after treatment with propranolol, and after antithyroid drugs. The first group of patients (n = 17) performed the following tests at all three assessment points: forced expiratory volume in the first second (FEV1), vital capacity (VC), functional residual capacity (FRC), residual volume (RV), total lung capacity (TLC), maximal mid-expiratory flow rate (MMFR), diffusing capacity for carbon monoxide (DLCO), and maximum static inspiratory and expiratory mouth pressures (PImax and PEmax). Arterial blood gas analysis was also performed for the first group of patients. No significant changes were seen either after propranolol or after antithyroid drugs in the FRC, RV, TLC, MMFR, DLCO, or blood gases. The remaining 18 patients, group 2, performed only the FEV1, VC, PImax, and PEmax tests at each assessment. The only index of respiratory function that improved significantly after propranolol was PImax (from 46.5 +/- 16.5 to 53.2 +/- 22 cmH2O, p less than 0.01). This suggests that adrenergic excess may play a role in thyrotoxic inspiratory muscle weakness. After antithyroid drugs, PImax, PEmax, FEV1, and VC all increased significantly as expected.

Adolescent↗
PubMed1988

Physical activity, muscle strength, and calcium intake in fracture of the proximal femur in Britain.

Regular exercise and high calcium intake possibly help to preserve bone mass. Little is known, however, about their role in preventing hip fracture. The physical activity and calcium intake of 300 elderly men and women with hip fractures were compared with those of 600 controls matched for age and sex. In both sexes increased daily activity, including standing, walking, climbing stairs, carrying, housework, and gardening protected against fracture. This was independent of other known risk factors, including body mass, cigarette smoking, and alcohol consumption. Strength of grip correlated with activity and was inversely related to the risk of fracture. Calcium intake was not related to the risk of fracture in women. Men with daily calcium intakes above 1g had lower risks. These findings point to the importance of elderly people in Britain maintaining physical activity in their day to day lives.

Activities of Daily Living↗
PubMedDate not supplied

Quantitative evaluation of knee instability and muscle strength after anterior cruciate ligament reconstruction using patellar and quadriceps tendon.

Anterior cruciate ligament reconstruction using an autologous graft harvested from the central one-third of the patellar and quadriceps tendon was performed in 65 knees of 65 patients who were followed from 3 to 7 years. Mean anterior laxity of both knees was measured before and after surgery in each patient using the Styker Knee Laxity Tester. At 30 degrees of knee flexion, 58 patients (89%) had differences of less than 2.5 mm between the operated and unoperated knees. Quadriceps strength was measured with the Cybex II and was less than 50% of the uninjured knee at 3 months after surgery. In men, quadriceps strength returned to 78% of normal at 1 year and 85% at final followup. These values were equal to the preoperative level. In women, the quadriceps strength at final followup was 70%, significantly lower than preoperative strength. Hamstring strength recovered to equal the normal strength. Although anterior cruciate ligament reconstruction using one-third of the patellar and quadriceps tendon achieves stability, postoperative quadriceps weakness is a disadvantage. This weakness may be caused by impairment of the knee extensor mechanism resulting from harvesting the graft. We do not currently recommend this technique for anterior cruciate ligament reconstruction.

Adolescent↗
PubMed2001

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work.

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but nonstrength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P < 0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg.kg body mass-1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg.kg body mass-1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance.

Adult↗
PubMed1992

Residual bone-mineral density and muscle strength after fractures of the tibia or femur in children.

This study compared the bone-mineral density in the proximal part of the femur and the flexion and extension strength of the knee in the fractured and the non-fractured limbs after an uncomplicated fracture of the tibia or femur in children. Thirty-eight children, whose ages ranged from two to fifteen years at the time of the injury, were evaluated at an average of 2.3 years after the injury. The mean difference in bone-mineral density between the fractured and non-fractured limbs was 3.3 per cent (p = 0.004). There was no significant difference between the bone-mineral density of the limbs that had been immobilized for less than four weeks and that of the contralateral, non-fractured limbs. However, the mean difference between the bone-mineral density of the limbs that had been immobilized for more than eight weeks and that of the contralateral limbs was 4.3 per cent (p = 0.006). There was little or no relationship between the time since the injury and the difference in bone-mineral density between the two limbs of the patient at the intervals of follow-up that were studied. No residual weakness in flexion and extension of the knee was detected, and no relationship was established between the limb-to-limb differences in strength and the limb-to-limb differences in bone-mineral density. The residual bone-mineral deficit was found to be minimum after an uncomplicated fracture. This difference, while statistically significant, is unlikely to be clinically important in the long term. However, the fact that there was a deficit raises a potential concern for children who have more severe or repeated injuries.

Adolescent↗
PubMed1997

Characteristics of body composition and muscle strength in college Sumo wrestlers.

The purpose of this study was to investigate the characteristics of body composition and force generation capacity in college Sumo wrestlers (N=13, age=19.8+/-0.3 yr, stature= 178.5+/-1.6 cm, body mass = 111.2+/-3.8 kg, X+/-SE) in comparison with untrained males (N=18, 20.3+/-0.2 yr, 170.1+/-1.7 cm, 59.2+/-1.4 kg). The Sumo wrestlers had significantly higher average values in relative fat mass (24.8+/-1.0%) and fat-free mass (83.3+/-2.0 kg), estimated by an underwater weighing method, than the untrained subjects (relative fat mass = 12.9+/-0.1 %, fat-free mass = 51.5+/-1.3 kg). Moreover, the Sumo wrestlers had 1.7 to 1.9 times greater cross-sectional areas (CSAs) of elbow flexors and extensors and knee extensors, determined by a B-mode ultrasound technique, compared to those of the untrained subjects. Force values produced during elbow flexion and extension and knee extensions tasks under isokinetic contraction mode at constant velocities of 1.05, 3.14 and 5.24 rad x s(-1) were significantly higher in the Sumo wrestlers than in the untrained subjects. The force value in all test conditions was significantly correlated to the related-muscle CSA, r=0.611-0.910 (p<0.05). The difference between the two groups in force per unit CSA (F x CSA[-1]) during elbow flexion was not significant at all test velocities. However, the Sumo wrestlers showed significantly lower F x CSA(-1) values in elbow extension at 5.24 rad x s(-1) and in knee extension at all test velocities. Thus, the body composition of the Sumo wrestlers was characterized by a high fat content and a large fat-free mass. Moreover, the Sumo wrestlers had considerably larger muscle CSAs of limbs than the untrained subjects. For the Sumo wrestlers, however, force output of the muscles with a pennate structure were not proportional to their CSAs, particularly in knee extensors.

Adipose Tissue↗
PubMed1989

Muscle strength, activity, housing and the risk of falls in elderly people.

In a national survey in Britain, 983 elderly people randomly selected from eight areas were asked about falls they had had in the past. The independent association of social and physical variables with a history of one or more falls was analysed by multiple logistic regression. Those who had fallen one or more times had reduced grip strength and were less mobile than those who had not fallen. More of them used non-phenothiazine tranquilizers, lived alone, had recently lost weight or were physically disabled. Independent of these influences, a history of having fallen was strongly related to place of residence. Part of this relationship was explained by differences in housing, in particular the percentage of houses without indoor lavatories.

Accidents, Home↗
PubMed1991

[Inspiratory muscle strength and endurance in patients with chronic obstructive pulmonary disease].

The maximal inspiratory pressure (MIP) and the sustainable inspiratory maximal pressure (SIPm) in 79 patients with chronic obstructive pulmonary disease (COPD) which were divided into the mild group (MG) and the mid-severe group (MSG) were measured. The results showed that MIP and SIPm were significantly lower in MSG than the prediction and in MG, the inspiratory fatigue in MSG was taken place in lower load and shorter time. We considered: MIP and SIPm fallen significantly in COPD patients might play a very important role in developing patients' respiratory failure.

Aged↗