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PubMed1986

Sympathetic response to maximal bicycle exercise before and after leg strength training.

Plasma catecholamine concentrations at rest and in response to maximal exercise on the cycle ergometer (278 +/- 15 watts, 6 min duration) have been measured on seven young active male subjects (19 +/- 1 years old; 80 +/- 3 kg; 176 +/- 3 cm) prior to and after a eight week leg strength training program (5RM, squat and leg press exercise). Strength training resulted in a significant increase in performance on squat (103 +/- 3 to 140 +/- 5 kg) and leg press exercise (180 +/- 9 to 247 +/- 15 kg) associated with a small significant increase in lean body mass (64.5 +/- 2.2 to 66.3 +/- 2.1 kg) and no change in maximal oxygen consumption (47.5 +/- 1.3 to 46.9 +/- 1.2 ml X kg-1 X min-1). Plasma norepinephrine (NE) and epinephrine (E) concentrations (pg X mL-1) were not significantly different before and after training at rest (NE: 172 +/- 19 vs 187 +/- 30; E: 33 +/- 10 vs 76 +/- 16) or in response to maximal exercise (NE: 3976 +/- 660 vs 4163 +/- 1081; E: 1072 +/- 322 vs 1321 +/- 508). Plasma lactate concentrations during recovery were similar before and after training (147 +/- 5 vs 147 +/- 15 mg X dL-1). Under the assumption that the "central command" is reduced for a given absolute workload on the bicycle ergometer following leg strength training, these observations support the hypothesis that the sympathetic response to exercise is under the control of information from muscle chemoreceptors.

Adult↗
PubMed1975

A study on the rehabilitation of ischemic heart disease patients. The heart rate, beta-receptor blocking agents and strength-duration relationship of exercise.

Exercise tests with bicycle ergometer were performed in 9 normals and 54 patients with ischemic heart disease (IHD), in order to evaluate the heart rate (HR) as a parameter for determining the physical working capacity and controlling the daily activities, and to observe the circulatory and metabolic effects of beta-blockers and moreover to study the strength-duration relationship of exertion. The following results were obtained and discussed: 1. Reliable correlation between heart rate and O2 consumption during all phases of exercise, including the recovery period (R = 0.60-0.87, p less than 0.001) and parallelism of heart rate and pressure rate product allows the heart rate to be used as a parameter for myocardial O2 demand and ST-T changes. It is reasonable to evaluate the exercise effect by the net increment of heart rate during and after exercise, and to utilize the increment of heart rate in the recovery period for the evaluation of physical fitness and adaptability. 2. Similar to other studies made on beta-blockers, in this study too, the agents including Kö 1366 suppressed the exercise responses of heart rate (p less than 0.01), the product of heart rate and blood pressure (p less than 0.01), and O2 consumption (p less than 0.01). But a relatively slow recovery of O2 consumption from the peak response towards pre-exercise level and a higher O2 pulse in the early recovery period was observed after beta-blocker medication. 3. Capillary (ear lobe) pH decreased and recovered in correlation with the strength of exertion. This corresponded with the response of other factors such as ST-T, heart rate, pressure-rate product, and O2 consumption, showing that the exercise strength was one of the more dominant factors to determine allowable work load for ischemic heart disease patients. 4. Recovery of pH was delayed after medication with Kö 1366 (p less than 0.01).

Adrenergic beta-Antagonists↗
PubMed1995

Intermittent pneumatic compression effect on eccentric exercise-induced swelling, stiffness, and strength loss.

OBJECTIVE: The purpose was to determine if intermittent pneumatic compression (IPC) affects muscle swelling, stiffness, and strength loss resulting from eccentric exercise-induced injury of the elbow flexors. We hypothesized that the compression would decrease swelling and stiffness. DESIGN: Repeated measures design with a before-after trial comparison within each day. SETTING: Conducted at a university Somatic Dysfunction Laboratory. SUBJECTS: Twenty-two college women students were studied. They had not been lifting weights or otherwise participating in regular arm exercise for the 6 months before the study. They had no history of upper extremity injury or cardiovascular disease. INTERVENTIONS: Subjects performed one bout of eccentric exercise at a high load to induce elbow flexor muscle injury. Uniform IPC was applied on the day of exercise and daily for 5 days at 60mmHg, 40 seconds inflation, 20 deflation for 20 minutes. MAIN OUTCOME MEASURES: Measurements of arm circumference, stiffness, and isometric strength were recorded before exercise, then before and after IPC for 5 days after exercise. Passive muscle stiffness was measured on a device that extends the elbow stepwise and records the torque required to hold the forearm at each elbow angle. RESULTS: Circumference and stiffness increased and strength decreased during the 5 days post-exercise (p < .05). IPC significantly decreased circumference and stiffness most notably on days 2 and 3 after exercise (p < .05). The strength loss was not affected by IPC. CONCLUSION: IPC is effective in temporarily decreasing the swelling and stiffness after exercise-induced muscle injury.

Adult↗
PubMed2001

Is glucose/amino acid supplementation after exercise an aid to strength training?

BACKGROUND: The precise timing of carbohydrate and amino acid ingestion relative to a bout of resistance exercise may modulate the training effect of the resistance exercise. OBJECTIVE: To assess whether regular glucose/amino acid supplementation immediately after resistance exercise could enhance the gain in muscle strength brought about by resistance training. METHODS: Seven untrained participants with a median age of 23 years and mean (SD) body mass 68.9 (13.5) kg resistance trained on a leg extension machine for five days a week for 10 weeks, using four sets of 10 repetitions. Alternate legs were trained on successive days, one leg each day. Subjects ingested either a supplement including 0.8 g glucose/kg and 0.2 g amino acids/kg, or placebo, on alternate training days immediately after training. Therefore the supplement was always ingested after training the same leg (supplement leg). Isometric, isokinetic, and 1 repetition maximum (RM) strength were measured before, during, and after training. Blood samples were analysed to determine the acute responses of insulin and glucose to resistance exercise and supplementation or placebo. RESULTS: Serum insulin concentration peaked 20 minutes after supplement ingestion at ninefold the placebo level, and remained significantly elevated for at least 80 minutes (p<0.01). Isometric, isokinetic, and 1 RM strength improved on both supplement and placebo legs (p<0.05). There were no significant differences in the gain in strength between the supplement leg and the placebo leg (p>0.05). CONCLUSION: Regular glucose/amino acid supplementation immediately after resistance exercise is unlikely to enhance the gain in muscle strength brought about by resistance training.

Adult↗
PubMed1997

Exercise adherence for a strength training program in older adults.

The first purpose of the present investigation was to examine initiation of a moderate intensity strength training and flexibility program in older adults. The second purpose was to assess adherence to training six months after conclusion of the initiation period. Forty-six apparently healthy older adults (mean age = 71.3; 33 women; 13 men) trained one hour, three days a week, for 4 months on a Nautilus Multi-Station Unit. The subjects trained on five upper extremity, three trunk, and three lower extremity stations. Training sessions consisted of 50 minutes of strength training and 10 minutes of flexibility exercises. Baseline exercise habits were obtained from the subjects using the Physical Exercise Profile (PEP). Subjects also completed portions of the PEP immediately following the conclusion of the 4-month intervention and 6 months later. The data were analyzed by chi square contingency tables. The subjects had over a 95% initiation rate during the study. Exercise leadership and program organization were found to be the most important reasons for the high initiation rate. Two determinants that influenced older adults to continue training were identified: satisfaction with the exercise routine and body image. These results indicate that exercise programs designed for older adults should emphasize exercise leadership to facilitate program initiation and subsequent exercise adherence.

Aged↗
PubMedDate not supplied

Exercise effects on the strength of the rat anterior cruciate ligament.

Seventy-five rats were divided into a control and four exercise groups of differing frequency and duration. After 8 weeks of endurance-type exercise on a motorized treadmill, the rats were sacrificed and the anterior cruciate ligaments were tested to failure on an Instron materials testing machine at a strain rate of 95% sec-1. Of the 121 ligaments tested, 119 failed by pure interstitial failure. There was significant increase in both the strength and stiffness of the anterior cruciate ligaments in the exercised rats but those rats exercised more frequently (daily vs. every other day) and for shorter duration (30 min rather than 60 min) had the greatest increase in strength. This study has shown that endurance-type exercise is beneficial to the anterior cruciate ligament as both strength and stiffness are increased and functionally the ligament remains unchanged by exercise.

Animals↗
PubMed1992

Strength changes induced by extreme dieting and exercise in severely obese females.

Strength changes, induced by very low-calorie diet (VLCD, 520 kcal/day) alone and in combination with exercise, were determined in 109 severely obese females (46.8 +/- 4.69% fat). Experimental treatments included VLCD alone (LC, n = 40), VLCD with endurance exercise (EE, n = 23), VLCD with endurance exercise and resistance strength training (EERST, n = 23), and VLCD with resistance strength training (RST, n = 23). All subjects participated in the study for 90 days while EE, EERST, and RST exercised four times/week according to specified schedules. Results indicated significant differences for the change scores (baseline to 90 days) for bench press, knee flexion, upper body and lower body composite strength scores between RST and all other groups. RST was the only treatment that increased upper and lower body strength. No differences between groups were found for body mass losses, decrease in percent fat and fat mass. In contrast, these variables showed significant change scores for all groups. Decreases in fat-free mass (FFM) were 5.18 +/- 3.40 kg, 4.79 +/- 4.15 kg (p = 0.001), 4.64 +/- 4.23 kg, and 3.26 +/- 2.67 kg for EE, LC, RST, and EERST, respectively. These data suggest that the combination of resistance strength training and VLCD increases strength despite a loss of FFM. However, endurance exercise and VLCD do not seem to affect body mass loss or FFM loss per se. Moreover, it seems that these increases in strength may represent a training effect which might imply improved central neuromuscular function rather than muscular hypertrophy since FFM decreased in all groups.

Adipose Tissue↗
PubMed1997

Hormone replacement therapy does not augment gains in muscle strength or fat-free mass in response to weight-bearing exercise.

Lower extremity strength and fat-free mass were examined in 58 postmenopausal women aged 60-72 yr. Subjects were studied before and after an 11-mo control period (n = 16) or before and after an 11-mo weight-bearing exercise training program designed to generate relatively high ground reaction forces (n = 42). Twenty-two of the exercisers initiated hormone replacement therapy (HRT) at the outset of exercise and continued HRT for 11 mo. Hip extension and abduction strength were assessed using a hand-held dynamometer. Force production during knee extension and flexion was evaluated on an isokinetic dynamometer at 60, 90, and 180 degrees/s. Simultaneous knee and hip extension strength was also assessed on a leg press machine. Total body and lower extremity fat-free mass were determined using dual-energy x-ray absorptiometry. There were no significant changes in muscle strength or body composition in control subjects. Both exercise groups had significant increases in fat-free mass and in all strength measures. Fat-free mass increased from 38.8 +/- 4.3 to 39.7 +/- 4.3 kg in the exercise group and from 37.7 +/- 3.9 to 38.9 +/- 4.6 kg in the exercise-plus-HRT group. The average relative increase in strength was 16.2 +/- 11.0% in the exercise group and 17.0 +/- 13.0% in the exercise-plus-HRT group. Women receiving HRT did not have a gain in fat-free mass or in strength over and above that demonstrated by the women not on HRT. Our results provide evidence that HRT does not augment the increases in muscle mass or strength that occur in response to weight-bearing exercise in older women.

Absorptiometry, Photon↗
PubMed1986

Structural changes in skeletal muscle tissue with heavy-resistance exercise.

Muscle strength, muscle cross-sectional area, fiber size, fiber type distribution, capillarity, and mitochondrial volume were estimated before and after 6 weeks of heavy-resistance exercise. Isokinetic torque production of the knee extensor muscles increased by a total of 17.6%, mainly during the first half of the training period. The cross-sectional area of the vastus lateralis muscle increased by 8.4%, mainly during the second half of the training period. Morphometrically determined fiber size, fiber type distribution, and capillarity from biopsies of vastus lateralis did not change significantly with training. Likewise, the surface densities of inner and outer mitochondrial membranes as well as the volume density of myofibrils remained unchanged. In contrast, the volume density of mitochondria decreased by 9.6%. However, due to the increase in total muscle volume, the calculated absolute volume of mitochondria remained constant, whereas the absolute volume of myofibrils increased by 10%. It is concluded that strength training of short duration in previously untrained young male subjects does not change the ultrastructural composition of mitochondria and that the apparent dilution of mitochondria can quantitatively be accounted for by the increase in myofibrillar volume.

Adenosine Triphosphatases↗
PubMed2000

A lifetime of fitness. Exercise in the perimenopausal and postmenopausal woman.

The peri- and postmenopausal woman experiences physiologic changes of aging that include alterations in hormone levels. Research has shown that the perimenopausal and postmenopausal woman can benefit significantly from exercise, whether endurance or strength training. Exercise can improve the quality of life and attenuate some of the physiologic changes associated with aging. Additionally, exercise can ameliorate the decline in fitness and bone, prevent chronic disease, and promote functional independence. Women who exercise regularly throughout life are physiologically 20 to 30 years younger than their sedentary counterparts. Fitness is a lifetime endeavor that has many positive benefits. Weightbearing activities are especially important as bone loss increases in the perimenopausal phase of life. Women should perform aerobic exercise 3 to 7 days per week for 15 to 60 minutes at 65% to 70% HRreserve. Strengthening exercises should be done 2 to 3 days per week at 40% to 80% 1RM with appropriately selected exercises. An exercise program should be functional and enjoyable. There is no better motivation to exercise than having a partner to work out with and keep the motivation alive. Most important, age itself is not a deterrent to exercise.

Body Composition↗
PubMed1989

Applicability of a threshold loading device for inspiratory muscle testing and training in patients with COPD.

We evaluated application of a Pth device for testing inspiratory muscle endurance among patients with severe but stable COPD. Endurance time in five patients was reproducible. Magnitude of variability was +/- 1.26 minutes with a range of +/- 0.19 to +/- 2.28 minutes. Eleven inpatients completed inspiratory muscle training twice daily for four weeks in addition to their usual program of respiratory rehabilitation. The mean age of our experimental cohort was 65 years; FEV1, 33 +/- 12 percent predicted; and Dsb, 42 +/- 7 percent predicted. Baseline measurements showed no significant differences in pulmonary function, exercise tolerance, inspiratory muscle strength or inspiratory muscle endurance between control and study groups. Following training, the study group significantly improved inspiratory muscle endurance as evidenced by an increase in endurance time while breathing against the same absolute external Pth load used during baseline assessments. There were no associated changes in lung mechanics, muscle strength or exercise tolerance.

Aged↗
PubMedDate not supplied

Left ventricular function during strength testing and resistance exercise in patients with left ventricular dysfunction.

PURPOSE: Deterioration in left ventricular function is a more sensitive marker of myocardial ischemia during exercise than ST segment depression. The current study was designed to evaluate left ventricular function during one-repetition-maximum (1-RM) strength testing and resistance exercise in cardiac patients with moderate left ventricular dysfunction. METHODS: Using echocardiographic methods, left ventricular function was evaluated in 15 patients with left ventricular dysfunction (age, 65 +/- 6.5 years; ejection fraction, 42.1 +/- 5.8). Measurements were performed during 1-RM testing and resistance exercise (20%, 40%, and 60% of 1-RM using 10 to 15 repetitions) on the one-arm biceps curl (BIC) and bilateral knee extension exercises and compared with measurements of left ventricular function during the symptom-limited graded exercise test (SL-GXT). RESULTS: During the knee extension exercise, there was a slight but significant reduction (P< or =.05) in ejection fraction values at the end of 60% 1-RM, as compared with rest and previous workloads. Significant increases in systolic blood pressure and left ventricular end-systolic volume ratio values (P< or =.05) from rest to exercise were observed across test modes and for all workloads. The prevalence of new wall motion abnormalities during knee extension and BIC 1-RM strength testing was comparable with that observed during SL-GXT. The greatest increase in new wall motion abnormalities was seen during 60% 1-RM of knee extension exercise, as compared with prior workloads, BIC exercises, and SL-GXT. CONCLUSIONS: Despite an increase in occurrence of ischemic changes during the highest resistance exercise workloads and with larger muscle mass, the findings are small in magnitude and do not suggest reduced cardiac performance.

Aged↗
PubMedDate not supplied

Influence of noninvasive ventilation by BiPAP on exercise tolerance and respiratory muscle strength in chronic obstructive pulmonary disease patients (COPD).

This study aimed to assess the effect of BiPAP, by nasal mask, on exercise tolerance and respiratory muscle strength in patients with a clinical and spirometric diagnosis of moderate/severe COPD (FEV1 < 60% of predicted). Ten patients of 59.4+/-8.9 years old, with FEV1/FVC <70% of predicted level, were treated with 30 minutes of BiPAP (IPAP:10 and 15 cmH2O; EPAP:4 cmH2O), three days per week, during two months. Before and after the treatment, spirometry, inspiratory (MIP) and expiratory (MEP) muscle strength and the distance walked in six minutes (6MWT) were measured. We observed a significant increase (Wilcoxon, p<0.05) in the mean values of MIP (from -55+/-17 to -77+/-19, respectively), MEP (from 75+/-20 to 109+/-36, respectively) and walking distance (from 349+/-67 to 448+/-75). Based on these results, we concluded that BiPAP improves respiratory muscle strength and exercise tolerance in these COPD patients.

Aged↗
PubMed2000

Changes in leg strength 8 and 32 h after endurance exercise.

The aim of this study was to determine the effects of a single bout of endurance exercise on subsequent strength performance. Eight males with a long history of resistance training performed isokinetic, isometric and isotonic leg extension strength tests 8 and 32 h after 50 min of cycle ergometry at 70-110% of critical power. The participants also completed a control condition in which no cycling was performed. Plasma lactate and ammonia were measured before and immediately after each strength test. Isokinetic, isometric and isotonic leg extension torques were not significantly different 8 or 32 h after endurance exercise compared with the control condition (P > 0.05). A large (50.3%), but not statistically significant, increase in plasma ammonia was evident during the strength tests performed 8 h after endurance exercise, while a significant (P < 0.05) increase in ammonia was also seen 32 h after endurance exercise. No significant changes in plasma ammonia were evident in the control condition. Our results suggest that leg extension strength was not compromised by an earlier bout of endurance cycling. However, metabolic activity during the strength tests might have been altered by the preceding bout of endurance exercise.

Adult↗
PubMed2001

Characteristics of isometric and dynamic strength loss following eccentric exercise-induced muscle damage.

Angle-specific isometric strength and angular velocity-specific concentric strength of the knee extensors were studied in eight subjects (5 males and 3 females) following a bout of muscular damaging exercise. One hundred maximal voluntary eccentric contractions of the knee extensors were performed in the prone position through a range of motion from 40 degrees to 140 degrees (0 degrees = full extension) at 1.57 rads(-1). Isometric peak torque was measured whilst seated at 10 degrees and 80 degrees knee flexion, corresponding to short and optimal muscle length, respectively. Isokinetic concentric peak torque was measured at 0.52 and 3.14 rad x s(-1). Plasma creatine kinase (CK) activity was also measured from a fingertip blood sample. These measures were taken before, immediately after and on days 1, 2, 4, and 7 following the eccentric exercise. The eccentric exercise protocol resuited in a greater relative loss of strength (P< 0.05) at short muscle length (76.3 +/- 2.5% of pre-exercise values) compared to optimal length (82.1 +/- 2.7%). There were no differences in the relative strength loss between isometric strength at optimal length and isokinetic concentric strength at 0.52 and 3.14 rad x s(-1). CK activity was significantly elevated above baseline at days 4 (P < 0.01) and 7 (P < 0.01). The greater relative strength loss at short muscle length appeared to persist throughout the seven-day testing period and provides indirect evidence of a shift in the angle-torque relationship towards longer muscle lengths. The results lend partial support to the popping sarcomere hypothesis of muscle damage, but could also be explained by an impairment of activation at short muscle lengths.

Adult↗
PubMed1987

Analysis of strength tests and resistive exercises commonly used for low-back disorders.

Using a modeling approach the conventional sit-up, the double straight-leg lowering, and prone trunk extension, the authors have shown these to have limitations as tests of maximum trunk flexion and extension strength and as modes of resistive exercise. These maneuvers are poor discriminators of trunk muscle strength, and they lack the range of resistance necessary to cover the spectrum of human trunk muscle strength capability. Use of manually handled weights can improve the above clinical tests and resistive exercise methods. As a result of selective positioning of the weights, variable resistance above and below that provided by the body segments alone can be achieved. The partial sit-up may be appropriate only for patients with significant trunk flexion weakness, and the straight head-trunk sit-up may be useful as a more strenuous test and resistive exercise. Rationale and derivations of the rigid-body equilibrium equations, as well as some of the limitations and assumptions associated with the modeling approach, are presented.

Adult↗