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PubMed2005

The effect of different intensity modalities of resistance training on beat-to-beat blood pressure in cardiac patients.

BACKGROUND: Resistance training has been introduced in cardiac rehabilitation to give more benefit than traditional training. Haemodynamic evaluation of cardiac patients to resistance training has generally consisted of continuous HR monitoring and discontinuous blood pressure measurements. DESIGN AND METHODS: Blood pressure (BP) and heart rate (HR) responses to resistance training were evaluated using continuous monitoring (Finapres) during low (four sets of 17 repetitions at 40% of the one-repetition maximum strength [1-RM]) and high intensity resistance training (four sets of 10 repetitions at 70% of 1-RM) on a leg extension machine in 14 patients who participated in a rehabilitation programme. Work volume was identical in the low- and high-level resistance training. RESULTS: The HR and systolic blood pressure (SBP) during low intensity resistance training were always larger than during high intensity (P<0.001). Peak SBP increased from set 1 to set 3 and 4 during both low and high intensity resistance training (P<0.05). Peak HR was larger in set 4 (95+/-11 bpm) than in set 1 only during low intensity resistance training (91+/-12 bpm) (P<0.05). One-minute recovery periods did not allow a return to baseline HR and SBP during both low and high intensity modalities. CONCLUSIONS: The SBP and HR responses to resistance training are related to the duration of exercise. Sets with < or =10 repetitions of high intensity should be preferred to longer sets with low intensity. Pauses between exercise sets should exceed 1 min. Blood pressure should be measured during the last repetitions of the exercise set.

Aged↗
PubMed2006

Chronic neural adaptation induced by long-term resistance training in humans.

While it is known that resistance training causes changes in the central nervous system (CNS) in the initial stages of training, there have been few studies of cumulative or sustained neural adaptation to resistance training beyond the initial periods. To further investigate this we compared the electromyographic (EMG) response to transcranial magnetic stimulation (TMS) during voluntary contractions of ten subjects who have been training for more than 2 years, resistance-training (RT) group, and ten subjects that have never participated in resistance training (NT). The active motor threshold for biceps brachii was obtained during voluntary elbow flexion at 10% of maximal voluntary contraction (MVC). TMS was also delivered at 100% of the maximal stimulator output while the participants exerted forces ranging from 10 to 90% of MVC. Evoked force, motor-evoked potential (MEP) amplitude and latency from biceps brachii was recorded for each condition to explore changes in corticospinal excitability. The evoked force was significantly lower in the RT group in comparison with the NT group between 30 and 70% of MVC intensity (P<0.05). At 90% of MVC, nine subjects from the RT group showed an absence in the evoked force while this occurred in only five subjects from the NT group. The MEP amplitude and latency changed significantly (P<0.001) with increasing levels of contraction, without significant difference between groups. These results indicate that changes in the CNS are sustained in the log-term practices of resistance training and permit a higher voluntary activation at several intensities of the MVC.

Adaptation, Physiological↗
PubMed1996

Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training.

Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% (P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 +/- 2.7 to 13.3 +/- 2.6 cm2; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases (P < 0.05) in fiber areas for type I (from 4,196 +/- 859 to 4,617 +/- 1,116 microns2; n = 11) and II fibers (from 6,378 +/- 1,552 to 7,474 +/- 2,017 microns2; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 +/- 61.5 x 10(3) pretraining; 297.5 +/- 69.5 x 10(3) posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly (P < 0.05) for both type I (from 4.9 +/- 0.6 to 5.5 +/- 0.7; n = 10) and II fibers (from 5.1 +/- 0.8 to 6.2 +/- 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.

Adenosine Triphosphatases↗
PubMed2002

The sites of neural adaptation induced by resistance training in humans.

Although it has long been supposed that resistance training causes adaptive changes in the CNS, the sites and nature of these adaptations have not previously been identified. In order to determine whether the neural adaptations to resistance training occur to a greater extent at cortical or subcortical sites in the CNS, we compared the effects of resistance training on the electromyographic (EMG) responses to transcranial magnetic (TMS) and electrical (TES) stimulation. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseous muscle of 16 individuals before and after 4 weeks of resistance training for the index finger abductors (n = 8), or training involving finger abduction-adduction without external resistance (n = 8). TMS was delivered at rest at intensities from 5 % below the passive threshold to the maximal output of the stimulator. TMS and TES were also delivered at the active threshold intensity while the participants exerted torques ranging from 5 to 60 % of their maximum voluntary contraction (MVC) torque. The average latency of MEPs elicited by TES was significantly shorter than that of TMS MEPs (TES latency = 21.5 +/- 1.4 ms; TMS latency = 23.4 +/- 1.4 ms; P < 0.05), which indicates that the site of activation differed between the two forms of stimulation. Training resulted in a significant increase in MVC torque for the resistance-training group, but not the control group. There were no statistically significant changes in the corticospinal properties measured at rest for either group. For the active trials involving both TMS and TES, however, the slope of the relationship between MEP size and the torque exerted was significantly lower after training for the resistance-training group (P < 0.05). Thus, for a specific level of muscle activity, the magnitude of the EMG responses to both forms of transcranial stimulation were smaller following resistance training. These results suggest that resistance training changes the functional properties of spinal cord circuitry in humans, but does not substantially affect the organisation of the motor cortex.

Adaptation, Physiological↗
PubMed1993

Effects of a 12-week resistive training program in the home using the body bar on dynamic and absolute strength of middle-age women.

Guidelines published by the American College of Sports Medicine indicate that resistive training should be an integral part of an adult fitness program. Most adults will find it difficult to train resistively regularly unless they train in their own homes using simple, inexpensive equipment. The purpose of this study was to examine the extent to which participation in a 12-week resistive training program using the Body Bar, a simple, inexpensive resistive training device, in the home improves dynamic and absolute strength of middle-age women compared to similar women engaged in a walking program. A pretest-midtest-posttest design was employed with subjects randomly assigned to either a resistive (n = 30) or a walking (control) group (n = 30). All subjects were tested on measures of dynamic and absolute strength. Resistive trainers performed significantly better than the controls across the 12-week training period on all strength variables even with statistical control for potential confounders. Number of workouts performed and average intensity of each workout were both significant predictors of strength improvements among the resistive trainers.

Adult↗
PubMed1989

Effects of resistive training on left ventricular function.

Although several studies have evaluated the effects of endurance training on left ventricular (LV) function, few studies have looked at resistive training effects. Acute isometric exercise increases blood pressure and has little effect on LV function, causing only mild increases in ejection fraction and stroke volume index. However, acute isometric exercise does increase LV diastolic diameter to a lesser extent than dynamic exercise. Most studies of resistive training on LV function have been cross-sectional or short term (10 to 12 wk) training studies on athletes and suggest that increases in LV wall thickness and mass are dependent upon the intensity and duration of training. Most resistive training studies show no increase in left ventricular volume, as can be seen in endurance trained athletes. Despite the increase in LV mass with resistive training, indices of LV systolic and diastolic function do not change. In hypertensive and cardiac patients with normal LV function at rest, resistive training increases LV mass index without deleterious effects on LV systolic and diastolic function. However, in patients with abnormal resting LV function, resistive training can have adverse effects on LV systolic function. Overall, moderate levels of resistive training can be a useful adjunct to cardiac rehabilitation programs, with the caveat that it be used with caution in patients with abnormal LV function at rest.

Coronary Disease↗
PubMed2001

Neural adaptations to resistance training: implications for movement control.

It has long been believed that resistance training is accompanied by changes within the nervous system that play an important role in the development of strength. Many elements of the nervous system exhibit the potential for adaptation in response to resistance training, including supraspinal centres, descending neural tracts, spinal circuitry and the motor end plate connections between motoneurons and muscle fibres. Yet the specific sites of adaptation along the neuraxis have seldom been identified experimentally, and much of the evidence for neural adaptations following resistance training remains indirect. As a consequence of this current lack of knowledge, there exists uncertainty regarding the manner in which resistance training impacts upon the control and execution of functional movements. We aim to demonstrate that resistance training is likely to cause adaptations to many neural elements that are involved in the control of movement, and is therefore likely to affect movement execution during a wide range of tasks. We review a small number of experiments that provide evidence that resistance training affects the way in which muscles that have been engaged during training are recruited during related movement tasks. The concepts addressed in this article represent an important new approach to research on the effects of resistance training. They are also of considerable practical importance, since most individuals perform resistance training in the expectation that it will enhance their performance in related functional tasks.

Adaptation, Physiological↗
PubMed2002

The association between adiposity and the response to resistance training among pre- and early-pubertal boys.

Resistance training has been shown to be effective in enhancing muscle strength among prepubertal and adolescent boys. Lately, it has been recommended for obese children. We hypothesized that resistance training will be similarly effective among boys of different adiposity. Thirty boys, aged 9.2 +/- 0.3 years, participated in progressive resistance training twice weekly during the first and second school years and thrice weekly during the third year. Training sessions included 1-4 sets of 3-6 exercises, with 5-30 repetitions/set. The mean load was 50-60% of 1 repetition maximum. Subjects were divided into responders (R--upper tertile) and non-responders (NR--lower tertile), according to the three-year improvement in muscle strength, as assessed by means of changes in concentric strength of knee flexors and extensors. Differences between groups were observed at baseline (p <0.05) in all variables reflecting adiposity (mean +/- SD): % body fat (14.1 +/- 2.6 vs 23.5 +/- 7.5% for R and NR, respectively), sum of four skinfolds (25.4 +/- 4.7 vs 47.8 +/- 21.6 mm for R and NR, respectively), BMI (15.5 +/- 1.1 vs 18.6 +/- 2.6 kg x m(-2) for R and NR, respectively). Additionally, the changes in adiposity were inversely related to the training effect (r = -0.60 to -0.34). No differences were observed in initial height and maturation between R and NR groups and there was no difference in linear growth and physical maturation with time between groups. These data suggest that resistance-training loads which may be appropriate to increase strength of knee flexors and extensors in normal-weight children may be insufficient to do so in overweight children. More research is required to elucidate the efficacy of resistance training among overweight children.

Adipose Tissue↗
PubMed2004

Resistance training for chronic heart failure patients on beta blocker medications.

BACKGROUND: Resistance training increases the skeletal muscle strength and functional ability of chronic heart failure patients. However, there is limited data regarding the effect of resistance training on the hemodynamic responses and peak oxygen consumption (peak VO(2)) of chronic heart failure patients treated with beta-blocker. This study examined the effect of resistance training on hemodynamics, peak aerobic capacity, muscle strength and quality of life of chronic heart failure patients on beta-blockers medication. METHODS: Fifteen men diagnosed with chronic heart failure were matched to either a resistance training program or non-training control group. At baseline and after 8 weeks of resistance training patients performed both Balke incremental and maximal strength tests and completed quality of life questionnaires. RESULTS: The resistance training group demonstrated a significant increase of walking time and peak VO(2) by 11.7% (p=0.002) and approximately 19% (p<0.05), respectively. Peak VO(2) was significantly correlated with both walking time (r=0.54, p=0.038) and change in total weight lifted (r=0.55, p=0.034). Quality of life significantly increased by 87% (p=0.030). The improvement in quality of life was correlated with post training peak VO(2) (r=0.58, p=0.025) and total weight lifted during the post maximal strength test (r=-0.52, p=0.047). CONCLUSIONS: The benefits from resistance training for chronic heart failure patients on beta-blocker medication included an increased aerobic and exercise capacity, skeletal muscle strength and most importantly, an improvement in the quality of life, which is the main goal of cardiac rehabilitation programs. Furthermore, with appropriate supervision, it is recommended that resistance exercise be added to the exercise rehabilitation program of these patients when possible.

Adaptation, Physiological↗
PubMedDate not supplied

Value of resistance training for the reduction of sports injuries.

Many competitive and recreational athletes perform resistance training as a part of their conditioning programmes. Resistance training in addition to increasing muscular strength and hypertrophy may also aid in the prevention of injuries. Research indicates that resistance training promotes growth and/or increases in the strength of ligaments, tendons, tendon to bone and ligament to bone junction strength, joint cartilage and the connective tissue sheaths within muscle. Studies involving humans and animal models also demonstrate resistance training can cause increased bone mineral content and therefore may aid in prevention of skeletal injuries. Investigations to date suggest resistance training can aid in injury prevention. The incidence of various types of overuse injuries, such as swimmers shoulder and tennis elbow, may be reduced by the performance of sport and/or motion specific resistance training activities. Screening of athletes for agonist and antagonist muscle strength imbalances can be utilised to identify possessing a predisposition for injury. Resistance training may then be performed to correct the imbalance and therefore reduce the incidence of injury.

Adaptation, Physiological↗
PubMed1996

Effect of age on muscle hypertrophy induced by resistance training.

BACKGROUND: Previous research has shown that resistance training induces muscle hypertrophy in older subjects, but has not clarified whether the degree of hypertrophy is affected by age. The present study was done to test the hypothesis that men and women over 60 years old have a smaller hypertrophic response to resistance training than young adults. METHODS: Cross-sectional areas (CSA) of muscle in the thigh and upper arm were determined before and after 3 months of progressive resistance training by magnetic resonance imaging (MRI) in 9 young (22-31 yr, 5 male and 4 female) and 8 old (62-72 yr, 4 male and 4 female) subjects. Strength was determined by 3-repetition-maximum (3RM) testing. The amount of weight lifted during the training program was proportional to baseline strength. RESULTS: Mean pretraining 3RM strength, per cm2 CSA, was less in the older group for all muscle groups examined (16 +/- 6% for elbow flexors, p < .02; 40 +/- 7% for knee flexors, p < .001; 19 +/- 9% for knee extensors, p < .05). Mean training-induced increases in muscle CSA were less in the older group for elbow flexors (22 +/- 4% in young, 9 +/- 4% in old, p < .05) and knee flexors (8 +/- 2% in young, 1 +/- 2% in old, p < .01), but not for knee extensors (4 +/- 1% in young, 6 +/- 2% in old). Mean training-induced increases in specific tension (ratio of 3RM strength to CSA) were similar in young and old groups for elbow flexors (21 +/- 5% in young, 19 +/- 5% in old) and knee extensors (38 +/- 6% in young, 32 +/- 14% in old), but were greater in the older group for knee flexors (28 +/- 5% in young, 64 +/- 13% in old, p < .02). CONCLUSIONS: Aging can attenuate the hypertrophic response of muscle groups to resistance training, when the training load is proportional to baseline strength. However, aging does not impair training-induced increases in specific tension.

Adult↗
PubMed2003

Carbohydrate supplementation and resistance training.

There is a growing body of evidence suggesting that the performance of resistance-training exercises can elicit a significant glycogenolytic effect that potentially could result in performance decrements. These decrements may result in less than optimal physiological adaptations to training. Currently some scientific evidence suggests that carbohydrate supplementation prior to and during high-volume resistance training results in the maintenance of muscle glycogen concentration, which potentially could result in the maintenance or increase of performance during a training bout. Some researchers suggest that ingesting carbohydrate supplements prior to and during resistance training may improve resistance-training performance. Additionally, the ingestion of carbohydrates following resistance exercise enhances the resynthesis of muscle glycogen, which may result in a faster time of recovery from resistance training, thus possibly allowing for a greater training volume. On the basis of the current scientific literature, it may be advisable for athletes who are performing high-volume resistance training to ingest carbohydrate supplements before, during, and immediately after resistance training.

Beverages↗
PubMed2004

The consequences of resistance training for movement control in older adults.

Older adults who undertake resistance training are typically seeking to maintain or increase their muscular strength with the goal of preserving or improving their functional capabilities. The extent to which resistance training adaptations lead to improved performance on tasks of everyday living is not particularly well understood. Indeed, studies examining changes in functional task performance experienced by older adults following periods of resistance training have produced equivocal findings. A clear understanding of the principles governing the transfer of resistance training adaptations is therefore critical in seeking to optimize the prescription of training regimes that have as their aim the maintenance and improvement of functional movement capacities in older adults. The degenerative processes that occur in the aging motor system are likely to influence heavily any adaptations to resistance training and the subsequent transfer to functional task performance. The resulting characteristics of motor behavior, such as the substantial decline in the rate of force development and the decreased steadiness of force production, may entail that specialized resistance training strategies are necessary to maximize the benefits for older adults. In this review, we summarize the alterations in the neuromuscular system that are responsible for the declines in strength, power, and force control, and the subsequent deterioration in the everyday movement capabilities of older adults. We examine the literature concerning the neural adaptations that older adults experience in response to resistance training, and consider the readiness with which these adaptations will improve the functional movement capabilities of older adults.

Adaptation, Physiological↗
PubMed1988

Cardiovascular adaptations to resistance training.

The cross-sectional and longitudinal data available indicate that the following conclusions are warranted concerning the effects of resistance training on the cardiovascular system. Resistance training causes increased absolute left ventricular wall thickness and left ventricular mass. These increases are not as evident when expressed relative to body surface area or lean body mass. There is little or no change in left ventricular internal dimensions, in absolute terms or relative to body surface area, resting heart rate, resting blood pressure, and diastolic function of the left ventricle due to resistance training. No change or slight positive effects are noted in systolic function of the left ventricle with training. During resistance training exercises, a large pressor response occurs and is attenuated in resistance trained athletes as compared to control subjects. Resistance training does result in adaptations of the cardiovascular system, with further research needed to elucidate its nature.

Adaptation, Physiological↗
PubMed2004

Effects of testosterone and resistance training in men with chronic obstructive pulmonary disease.

Dysfunction of the muscles of ambulation contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). Men with COPD have high prevalence of low testosterone levels, which may contribute to muscle weakness. We determined effects of testosterone supplementation (100 mg of testosterone enanthate injected weekly) with or without resistance training (45 minutes three times weekly) on body composition and muscle function in 47 men with COPD (mean FEV(1) = 40% predicted) and low testosterone levels (mean = 320 ng/dl). Subjects were randomized to 10 weeks of placebo injections + no training, testosterone injections + no training, placebo injections + resistance training, or testosterone injections + resistance training. Testosterone injections yielded a mean increase of 271 ng/dl in the nadir serum testosterone concentration (to the middle of the normal range for young men). The lean body mass (by dual-energy X-ray absorptiometry) increase averaged 2.3 kg with testosterone alone and 3.3 kg with combined testosterone and resistance training (p < 0.001). Increase in one-repetition maximum leg press strength averaged 17.2% with testosterone alone, 17.4% with resistance training alone, and 26.8% with testosterone + resistance training (p < 0.001). Interventions were well tolerated with no abnormalities in safety measures. Further studies are required to determine long-term benefits of adding testosterone supplementation and resistance training to rehabilitative programs for carefully screened men with COPD and low testosterone levels.

Aged↗
PubMed2002

Effect of creatine supplementation during high resistance training on mass, strength, and fatigue resistance in rat skeletal muscle.

The aim of this study was to utilize a rodent model of resistance exercise to compare training with creatine supplementation with training alone. We tested the hypothesis that creatine supplementation during high resistance training would result in greater increases in muscle mass, contractile force, and superior resistance to fatigue compared with training alone. Two groups of rats underwent training of the tibialis anterior muscle (TA) for 4 weeks without creatine (NCr group) or with creatine (0.5 g.kg(-1).d(-1)) (CrT group). The relative loads in each animal were held constant during the training protocol. Training resulted in comparable significant increases in muscle contractile force in both the NCr and CrT groups. Creatine supplementation did not result in a significant increase in fatigue resistance and resulted in a significant decrease in postfatigue recovery compared with training alone. Training resulted in a significant increase in muscle dry weight in both groups, whereas muscle wet weight gains in the CrT group were double the gains in the NCr group. The data from this study suggest that for creatine to have a beneficial effect on muscle strength and mass beyond training alone, the workloads need to be adjusted. That is, any potential benefit of creatine to enable a greater lifting volume during resistance training needs to be incorporated into the training regime for creatine to be effective.

Animals↗
PubMed1996

The effectiveness of resistance training in children. A meta-analysis.

Many recent studies have reported that resistance training can be effective in producing strength gains among prepubescents. These studies appear to refute the early claims of ineffectiveness of resistance training in children. A meta-analysis procedure combines the results of individual empirical studies and estimates a standardised effect, termed effect size. This effect size is based on the scores of the control and experimental groups before and after training. It defines the difference between the gain of the experimental and control groups, divided by the standard deviation of the pooled variances of both groups. A literature search revealed 28 studies which described a resistance training programme for girls and boys under the age of 12 and 13 years, respectively. Presumably, these children were pre- or early-pubescents. However, only 9 of these studies provided the necessary data to calculate the effect size and could be included in the analysis. The majority of the studies showed a gain in strength between 13 and 30%. The overall mean effect size was found to be 0.57. This signifies that following training, the average child in the resistance training group was above 71.6% of the children in the control group. The effectiveness of resistance training can be influenced by factors such as age and maturation, gender, as well as the frequency, duration and intensity of the training programme. The studies included in the analysis examined participants of varying ages and did not demonstrate a clear influence of age. Most studies examined only boys or a mixed group of boys and girls. Therefore, the influence of gender on the effectiveness of resistance training in prepubescents cannot yet be determined. Nevertheless, in the few studies where boys and girls were examined separately, no difference was found in the effect of resistance training between genders. It appears that a training frequency of twice per week is sufficient to induce strength gains in children. However, the minimal, or for that matter optimal, duration and intensity are not clear. Some of the weaknesses observed in the reviewed studies include: (i) the lack of control for a possible learning effect; (ii) non-randomisation into the training and control groups; (iii) no report of adherence rate; (iv) a reliance on boys as study participants; and (v) too little information on the type, volume and intensity of training. Future studies should take these weaknesses into consideration.

Age Factors↗