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Biomedical subjects

B F Hurley

Publications and source records attributed to B F Hurley.

At least 37 records · Page 2Linked to original sources
PubMed1999

Ultrastructural muscle damage in young vs. older men after high-volume, heavy-resistance strength training.

This study assessed ultrastructural muscle damage in young (20-30 yr old) vs. older (65-75 yr old) men after heavy-resistance strength training (HRST). Seven young and eight older subjects completed 9 wk of unilateral leg extension HRST. Five sets of 5-20 repetitions were performed 3 days/wk with variable resistance designed to subject the muscle to near-maximal loads during every repetition. Biopsies were taken from the vastus lateralis of both legs, and muscle damage was quantified via electron microscopy. Training resulted in a 27% strength increase in both groups (P < 0.05). In biopsies before training in the trained leg and in all biopsies from untrained leg, 0-3% of muscle fibers exhibited muscle damage in both groups (P = not significant). After HRST, 7 and 6% of fibers in the trained leg exhibited damage in the young and older men, respectively (P < 0.05, no significant group differences). Myofibrillar damage was primarily focal, confined to one to two sarcomeres. Young and older men appear to exhibit similar levels of muscle damage at baseline and after chronic HRST.

Actin Cytoskeleton↗
PubMed1998

Acute and chronic resistive exercise increase urinary chromium excretion in men as measured with an enriched chromium stable isotope.

Both exercise and chromium exert beneficial effects on insulin function. The mechanism by which exercise improves insulin response may involve an alteration in Cr metabolism. To determine the effects of acute and chronic resistive exercise on urinary Cr losses, we measured the effects of acute resistive exercise and 16 wk of resistive exercise training on urinary Cr losses of 10 men 53-63 y of age. Subjects consumed diets in compliance with the American Heart Association Phase I diet with a Cr content of 30 +/- 4 microg/d. Sixteen weeks of resistive exercise training led to approximately 40% increases in upper and lower body strength, increases in fat-free mass and decreases in the percentage of body fat. An enriched stable isotope of Cr, 53Cr, was employed to differentiate the exogenously administered Cr from the native endogenous Cr. Both acute and chronic resistive exercise increased 53Cr losses. These data demonstrate that the improvements in body composition due to resistive exercise are associated with increased urinary Cr losses that are consistent with increased absorption.

Adipose Tissue↗
PubMed1997

Safety and efficacy of strength training in patients with sporadic inclusion body myositis.

We studied the effects of a 12-week progressive resistance strength training program in weakened muscles of 5 patients with sporadic inclusion body myositis (IBM). Strength was evaluated with Medical Research Council (MRC) scale ratings and quantitative isometric and dynamic tests. Changes in serum creatine kinase (CK), lymphocyte subpopulations, muscle size (determined by magnetic resonance imaging), and histology in repeated muscle biopsies were examined before and after training. After 12 weeks, the values of repetition maximum improved in the least weakened muscles, 25-120% from baseline. This dynamic effect was not captured by MRC or isometric muscle strength measurements. Serum CK, B cells, T-cell subsets, and NK cells remained unchanged. Repeat muscle biopsies did not reveal changes in the number and degree of degenerating fibers or inflammation. The size of the trained muscles did not change. We conclude that a supervised progressive resistance training program in IBM patients can lead to gains in dynamic strength of the least weak muscles without causing muscle fatigue and muscle injury or serological, histological, and immunological abnormalities. Even though the functional significance of these gains is unclear, this treatment modality is a safe and perhaps overlooked means of rehabilitation of IBM patients.

Activities of Daily Living↗
PubMed1997

Age and gender comparisons of muscle strength in 654 women and men aged 20-93 yr.

To assess age and gender differences in muscle strength, isometric, concentric (Con), and eccentric (Ecc) peak torque was measured in the knee extensors at a slow (0.52 rad/s) and fast (3.14 rad/s) velocity in 654 subjects (346 men and 308 women, aged 20-93 yr) from the Baltimore Longitudinal Study of Aging. Regression analysis revealed significant (P < 0.001) age-related reductions in Con and Ecc peak torque for men and women at both velocities, but no differences were observed between the gender groups or velocities. Age explained losses in Con better than Ecc peak torque, accounting for 30% (Con) vs. 19% (Ecc) of the variance in men and 28% (Con) vs. 11% (Ecc) in women. To assess age and gender differences in the ability to store and utilize elastic energy, the stretch-shortening cycle was determined in a subset of subjects (n = 47). The older women (mean age = 70 yr) showed a significantly greater enhancement in the stretch-shortening cycle, compared with men of similar age (P < 0.01) and compared with younger men and women (each P < 0.05). Both men and women showed significant declines in muscle quality for Con peak torque (P < 0.01), but no gender differences were observed. Only the men showed a significant decline in muscle quality (P < 0.001) for Ecc peak torque. Thus both men and women experience age-related losses in isometric, Con, and Ecc knee extensor peak torque; however, age accounted for less of the variance in Ecc peak torque in women, and women tend to better preserve muscle quality with age for Ecc peak torque. In addition, older women have an enhanced capacity to store and utilize elastic energy compared with similarly aged men as well as with younger women and men.

Adult↗
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↗
PubMed1995

Effects of strength training on muscle hypertrophy and muscle cell disruption in older men.

To determine whether a total body, heavy resistance, strength training (ST) program can significantly increase muscle strength and hypertrophy without muscle cell disruption and soreness in older men, 35 sedentary male subjects between the ages of 50 and 69 years of age (60 +/- 5, mean +/- SD) were studied. Twelve served as inactive controls. Muscular strength, cross-sectional muscle area, serum creatine kinase (CK) activity and perceived soreness were assessed before and after a 16 wk heavy resistance ST program. The ST program resulted in a 43% increase in muscular strength (p < 0.001), and a 7.2% increase in midthigh muscle area (153 +/- 24 vs 164 +/- 23 cm2, p < 0.001). There were no significant changes in strength or muscle area in the inactive control group. Peak serum CK levels were approximately twofold above baseline (278 +/- 175 vs 133 +/- 88 U/l, p < 0.01) 8 h after the first regular training session. At the end of training, the peak rise in CK levels was also reached 8 h after exercise, but was reduced substantially at the same absolute (p < 0.01) and relative resistance loads (p < 0.01) compared to the first training session. Muscle soreness after exercise was only occasionally reported at the beginning of training and was almost nonexistent after training. These results indicate that middle-aged and older men can safely participate in a total body strength training program, intense enough to produce substantial increases in muscle strength and hypertrophy, without promoting muscle soreness or significant muscle cell disruption.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1995

Testosterone, growth hormone and IGF-I responses to acute and chronic resistive exercise in men aged 55-70 years.

We investigated the responses of serum testosterone (T) and human growth hormone (hGH) concentrations to a bout of heavy resistive exercise and the responses of T, hGH, and insulin-like growth factor I (IGF-I) to a 16 wk progressive resistive training program in 13 men (60 +/- 4 yrs). Body composition via hydrostatic weighing and muscle strength using a 3 repetition maximum (3RM) test on 6 variable resistance exercise machines were assessed before and after the training program. Fasting blood samples were drawn on 2 consecutive days prior to training and again on 2 consecutive days after the last day of exercise. Blood was also drawn immediately before and approximately 10 min after a single exercise session during the first wk of training, and after an exercise session of the same relative resistance during the last wk of training. The training program resulted in a 37% increase in upper body strength and a 39% increase in lower body strength (both p < 0.01). Lean body mass increased significantly (61.8 +/- 2.1 vs 63.7 +/- 7.8 kg; p < 0.001) while % fat decreased (26.5 +/- 1.5 vs 24.9 +/- 6.0%; p < 0.01) as a result of training. Serum T concentration was unchanged, but GH increased approximately 18-fold in response to a single bout of resistive exercise before (0.24 +/- 0.08 vs 4.60 +/- 1.35 mg/l) and after (0.26 +/- 0.06 vs 4.66 +/- 1.46 mg/l; p < 0.01) training. Baseline serum concentrations of T, hGH, and IGF-I were unaffected by the training program. We conclude that an acute bout of resistive exercise causes a substantial hGH response in older men, but 16 wks of progressive resistive training does not affect baseline concentrations of the anabolic hormones.

Aged↗
PubMed1995

Age, gender, and muscular strength.

Muscular strength can be measured by cable tensiometry, non-motorized dynamometry (e.g., handgrip dynamometer), motorized dynamometry, or with free weights or exercise machines. Advantages and disadvantages of each are discussed. Cross-sectional studies indicate that isometric and concentric strength levels peak between the second and third decade, remain unchanged until the fourth or fifth decade, and start to decline from about the fifth decade at a rate of 12% to 15% per decade until the eighth decade in men. Greater strength losses in both men and women have been suggested from the few longitudinal studies available on this topic. However, concentric strength levels in women tend to peak sooner, start to decline earlier, and decrease at a slightly slower rate than men. Age- and inactivity-induced sarcopenia explains some but not all of the losses in strength with age. There is a need to determine the separate roles of disease, inactivity, and normal aging on these losses. New findings from the Baltimore Longitudinal Study of Aging suggest a preservation of eccentric strength levels with age in women.

Adult↗
PubMed1995

Does strength training inhibit gains in range of motion from flexibility training in older adults?

Thirty-one untrained men between the ages of 50 and 74 (61 +/- 6 yr, mean +/- SD) were studied to compare the effects of strength and flexibility (SF) training, flexibility only (FO) training, and no training (inactive control group) on shoulder and hip range of motion. Fourteen of these subjects volunteered to participate in an SF training program three times per week for 10 wk. Ten others participated in an FO training program during this same time period, and the remaining seven subjects agreed to serve as an inactive control group by not participating in any regular exercise. The SF training consisted of a 3-min warm-up on a stationary bike, approximately 30 min of heavy resistance strength training, and about 10 min of static stretches performed before and after each training session. Maximal oxygen uptake (VO2max), percentage of body fat, and muscular strength (three-repetition maximum and peak isokinetic torque) were assessed before and after training for the SF group. Shoulder abduction, shoulder flexion, and hip flexion were measured with a universal goniometer in all groups before and after the training period. The FO training consisted of the identical warm-up and stretching exercises used in the SF training but without strength training. The results indicate that the FO group increased its range of motion in shoulder abduction to a significantly greater extent than the SF group (P < 0.001), and none of the changes in range of motion for the SF group was significantly different than the changes in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1994

Effects of exercise training modality on glucose tolerance in men with abnormal glucose regulation.

To determine the effects of exercise training modality on glucose tolerance in men with untreated abnormal glucose regulation, 26 untrained men (age 54 +/- 9 years; mean +/- SD) with either non-insulin-dependent diabetes mellitus (N = 8), impaired glucose tolerance (IGT) (N = 12) or hyperinsulinemia with normal glucose tolerance (N = 6) were studied before and after 20 wk of either strength training (ST) (N = 8), aerobic (treadmill walk/jog) training (AT) (N = 8), or no exercise (control group; N = 10). Plasma concentrations of glucose and insulin were measured after a 12-14 hr fast and during a standard oral glucose tolerance test (OGTT) before and after training. The ST program significantly reduced total plasma glucose area (mmol.l-1.120 min-1) under the OGTT curve (1348 +/- 251 vs 1190 +/- 329, p < 0.05), and plasma glucose levels (mmol.l-1) at 60 min (p < 0.05), 90 min (P < 0.05), and 120 min (p < 0.05) after glucose ingestion. Strength training also lowered the total plasma insulin area (pmol.l-1.120 min-1) under the OGTT curve (60082 +/- 25467 vs 46727 +/- 11273, p < 0.05) as well as plasma insulin levels (pmol.l-1) at fasting (p < 0.05) and at 90 min (p < 0.01) and 120 min (p < 0.05) after glucose ingestion. All men with IGT (four in each training group) normalized their glucose tolerance following the training. There were no significant differences in OGTT results between ST and AT and no changes were observed in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1994

Effects of strength training on total and regional body composition in older men.

The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 untrained healthy men [60 +/- 4 (SD) yr]. Nine additional men (62 +/- 6 yr) served as inactive controls. The strength-training program resulted in substantial increases in both upper (39 +/- 8%; P < 0.001) and lower (42 +/- 14%; P < 0.001) body strength. Total fat-free mass (FFM) increased by 2 kg (62.0 +/- 7.1 to 64.0 +/- 7.2 kg; P < 0.001), and total fat mass decreased by the same amount (23.8 +/- 6.7 to 21.8 +/- 6.0 kg; P < 0.001) when measured by DEXA. When measured by hydrodensitometry, similar increases in FFM (61.3 +/- 7.8 to 63.0 +/- 7.6 kg; P < 0.01) and decreases in fat mass (23.8 +/- 7.9 to 22.1 +/- 7.7 kg; P < 0.001) were observed. When measured by DEXA, FFM was increased in the arms (6.045 +/- 0.860 to 6.418 +/- 0.803 kg; P < 0.01), legs (19.416 +/- 2.228 to 20.131 +/- 2.303 kg; P < 0.001), and trunk (29.229 +/- 4.108 to 30.134 +/- 4.184 kg; P < 0.01), whereas fat mass was reduced in the arms (2.383 +/- 0.830 to 2.128 +/- 0.714 kg; P < 0.01), legs (7.583 +/- 1.675 to 6.945 +/- 1.551 kg; P < 0.001), and trunk (12.216 +/- 4.143 to 11.281 +/- 3.653 kg; P < 0.01) as a result of training.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1994

Strength training increases insulin action in healthy 50- to 65-yr-old men.

The insulin resistance associated with aging may be due, in part, to reduced levels of physical activity in the elderly. We hypothesized that strength training increases insulin action in older individuals. To test this hypothesis, 11 healthy men 50-63 yr old [mean 58 +/- 1 (SE) yr] underwent a two-step hyperinsulinemic-euglycemic glucose clamp with concurrent indirect calorimetry and an oral glucose tolerance test (OGTT) before and after 16 wk of strength training. The training program increased overall strength by 47% (P < 0.001). Fat-free mass (FFM; measured by hydrodensitometry) increased (62.4 +/- 2.1 vs. 63.6 +/- 2.1 kg; P < 0.05) and body fat decreased (27.2 +/- 1.8 vs. 25.6 +/- 1.9%; P < 0.001) with training. Fasting plasma glucose levels and glucose levels during the OGTT were not significantly lower after training. In contrast, fasting plasma insulin levels decreased (85 +/- 25 vs. 55 +/- 10 pmol/l; P < 0.05) and insulin levels decreased (P < 0.05, analysis of variance) during the OGTT. Glucose infusion rates during the hyperinsulinemic-euglycemic glucose clamp increased 24% (13.5 +/- 1.7 vs. 16.7 +/- 2.2 mumol.kg FFM-1.min-1; P < 0.05) during the low (20 mU.m-2.min-1) insulin infusion and increased 22% (55.7 +/- 3.3 vs. 67.7 +/- 3.9 mumol.kg FFM-1.min-1; P < 0.05) during the high (100 mU.m-2.min-1) insulin infusion. These increases were accompanied by a 40% increase (n = 7; P < 0.08) in nonoxidative glucose metabolism during the high insulin infusion. These results demonstrate that strength training increases insulin action and lowers plasma insulin levels in middle-aged and older men.

Aged↗
PubMed1994

Effects of strength training on bone mineral density: hormonal and bone turnover relationships.

The effects of a 16-wk strength-training program on bone mineral density (BMD) was assessed by dual-energy X-ray absorptiometry in 21 men [age 61 +/- 1 (SE) yr]. Sixteen men (age 59 +/- 2 yr) served as control subjects. To investigate the possible hormonal relationships underlying the effects on BMD, serum concentrations of growth hormone, insulin-like growth factor I, and testosterone were determined before and after training. In addition, osteocalcin and skeletal alkaline phosphatase (markers of bone formation) and tartrate-resistant acid phosphatase (a marker of bone resorption) were measured before and after training to assess bone turnover. The training program resulted in a 2.8 +/- 0.6% increase in femoral neck BMD (1.004 +/- 0.037 vs. 1.031 +/- 0.037 g/cm2; P < 0.001). However, there were no significant changes in total body, anterioposterior spine, lateral spine, Ward's triangle, or greater trochanter BMD. Moreover, there were no significant changes in growth hormone, insulin-like growth factor I, testosterone, osteocalcin, or skeletal alkaline phosphatase. There were no changes in the control group. Thus, strength training can increase femoral neck BMD, and this effect does not appear to be accompanied by changes in anabolic hormones or markers of bone formation and resorption.

Absorptiometry, Photon↗
PubMed1993

Effect of endurance training on plasma free fatty acid turnover and oxidation during exercise.

Plasma free fatty acid (FFA) levels tend to be lower and the plasma lipolytic hormone response to prolonged exercise of the same intensity is blunted after endurance exercise training. To determine whether training elicits a corresponding decrease in plasma FFA turnover and metabolism during prolonged exercise, we measured plasma [1-13C]palmitate kinetics and oxidation and respiratory gas exchange in 13 subjects during the latter portion of a 90- to 120-min bout of cycle ergometer work performed before and after 12 wk of alternate-day cycling and running. Training increased total fat oxidation during prolonged exercise by 41% (P < 0.005). However, for the final 30-60 min of the cycle ergometer protocol, the rate of 13CO2 production from [1-13C]palmitate oxidation was 27% lower (P < 0.05), the rate of palmitate turnover was 33% less (P < 0.05), and plasma FFA and glycerol concentrations were 32 and 20% lower (P < 0.05), respectively, than in the untrained state. Thus endurance exercise training results in decreased plasma FFA turnover and oxidation during a 90- to 120-min bout of submaximal exercise because of a slower rate of FFA release from adipose tissue.

Adult↗
PubMed1993

Strength training increases regional bone mineral density and bone remodeling in middle-aged and older men.

To determine the effects of strength training (ST) on bone mineral density (BMD) and bone remodeling, 18 previously inactive untrained males [mean age 59 +/- 2 (SE) yr] were studied before and after 16 wk of either ST (n = 11) or no exercise (inactive controls; n = 7). Total, spinal (L2-L4), and femoral neck BMD were measured in nine training and seven control subjects before and after the experimental period. Serum concentrations of osteocalcin, skeletal alkaline phosphatase isoenzyme, and tartrate-resistant acid phosphatase were measured before, during, and after the experimental program in all subjects. Training increased muscular strength by an average of 45 +/- 3% (P < 0.001) on a three-repetition maximum test and by 32 +/- 4% (P < 0.001) on an isokinetic test of the knee extensors performed at 60 degrees/s. BMD increased in the femoral neck by 3.8 +/- 1.0% (0.900 +/- 0.05 vs. 0.933 +/- 0.05 g/cm2, P < 0.05) and in the lumbar spine by 2.0 +/- 0.9% (1.180 +/- 0.06 vs. 1.203 +/- 0.06 g/cm2, P < 0.05). However, changes in lumbar spine BMD were not significantly different from those in the control group. There was no significant change in total body BMD. Osteocalcin increased by 19 +/- 6% after 12 wk of training (P < 0.05) and remained significantly elevated after 16 wk of training (P < 0.05). There was a 26 +/- 11% increase in skeletal alkaline phosphatase isoenzyme levels (P < 0.05) after 16 wk of training.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1992

Strength training accelerates gastrointestinal transit in middle-aged and older men.

Seven healthy, untrained men (age 60 +/- 2 yr, mean +/- SEM) were studied to determine the effects of a 13-wk total body strength training program on gastrointestinal transit time (GITT). Whole bowel transit time and mouth-to-cecum transit time were assessed before and after the training program. Subjects recorded dietary intake for the 5 d preceding their baseline GITT tests and repeated that diet for 5 d prior to their GITT tests after training. No significant changes in weight or VO2max were observed as a result of the training program. There was a small but significant decrease in body fat assessed by hydrodensitometry (23.4 +/- 2.6% vs 21.8 +/- 2.6%, P less than 0.05). The training program resulted in a 41 +/- 5% increase (P less than 0.001) in upper body strength and a 45 +/- 6% increase (P less than 0.001) in lower body strength. A 38 +/- 6% increase (P less than 0.01) in peak torque of the knee extensors was also observed at 60 degrees.s-1. The training program significantly accelerated whole bowel transit time (41 +/- 11 vs 20 +/- 7 hr; P less than 0.01). There was no significant change in mouth-to-cecum transit time. Thus, a strength training program can accelerate whole bowel transit time in previously sedentary middle-aged and older men. This effect appears to be in the large intestines.

Aged↗