Skeletal muscle characteristics among distance runners: a 20-yr follow-up study

The purpose of this investigation was to examine the histochemical and enzymatic characteristics of skeletal muscle after 20 yr of distance running training. Twenty-eight men were first studied between 1966 and 1974 when they were all highly trained distance runners. On the basis of their training regimens in the interim between testing, subjects were described as highly trained (HI; n = 11), fitness trained (FIT; n = 10), or untrained (UT; n = 7). Gastrocnemius muscle biopsy samples revealed a mean increase (P < 0.05) in the proportion of type I fibers of the FIT and UT groups, whereas the HI group, which was initially characterized by a high percentage (> 70%) of type I fibers, was unchanged. Although the mean fiber type change of the HI group was similar between evaluations, 6 of the 11 subjects did elicit an increase in the percentage of type I fibers. A subgroup of elite distance runners who had continued to train for competition experienced an approximately 25% reduction (P > 0.05) in muscle succinate dehydrogenase activity and decreases (P > 0.05) in types I and II muscle fiber areas. On the average, in 1993 the HI group had higher (P < 0.05) succinate dehydrogenase and citrate synthase activities than the FIT and UT groups, whereas phosphorylase activity did not differ among the three groups. These data suggest that the middle-aged men in this study had a significantly greater proportion of type I muscle fibers than when they were 20 yr younger.(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of glycogen accumulation after eccentric exercise

This study examined the time course of glycogen accumulation in skeletal muscle depleted by concentric work and subsequently subjected to eccentric exercise. Eight men exercised to exhaustion on a cycle ergometer [70% of maximal O2 consumption (VO2max)] and were placed on a carbohydrate-restricted diet. Approximately 12 h later they exercised one leg to subjective failure by repeated eccentric action of the knee extensors against a resistance equal to 120% of their one-repetition maximum concentric knee extension force (ECC leg). The contralateral leg was not exercised and served as a control (CON leg). During the 72-h recovery period, subjects consumed 7 g carbohydrate.kg body wt-1.day-1. Moderate soreness was experienced in the ECC leg 24-72 h after eccentric exercise. Muscle biopsies from the vastus lateralis of the ECC and CON legs revealed similar glycogen levels immediately after eccentric exercise (40.2 +/- 5.2 and 47.6 +/- 6.4 mmol/kg wet wt, respectively; P greater than 0.05). There was no difference in the glycogen content of ECC and CON legs after 6 h of recovery (77.7 +/- 7.9 and 85.1 +/- 4.9 mmol/kg wet wt, respectively; P greater than 0.05), but 18 h later, the ECC leg contained 15% less glycogen than the CON leg (90.2 +/- 8.2 vs. 105.8 +/- 8.9 mmol/kg wet wt; P less than 0.05). After 72 h of recovery, this difference had increased to 24% (115.8 +/- 8.0 vs. 153.0 +/- 12.2 mmol/kg wet wt; P less than 0.05). These data confirm that glycogen accumulation is impaired in eccentrically exercised muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of vitamin B-6 content of muscle to changes in vitamin B-6 intake in men

Previous reports indicated that in growing rats the vitamin B-6 pool in muscle was relatively stable during deficiency but increased in response to increased vitamin B-6 intake. To determine whether human muscle would show a similar response 10 college-aged males received a low vitamin B-6 diet (1.76 mumol/d) for 6 wk followed by 6 wk on a self-selected diet supplemented with 0.98 mmol pyridoxine HCl/d. During depletion, excretion of pyridoxic acid rapidly adjusted to approximate the intake. Plasma pyridoxal phosphate concentrations at the end of the baseline, depletion, and supplementation periods were 81 +/- 51, 9 +/- 3, and 455 +/- 129 nmol/L, respectively, whereas muscle concentrations were 21 +/- 9, 20 +/- 4, and 25 +/- 7 nmol/g, respectively and total vitamin B-6 in muscle was 28 +/- 10, 27 +/- 4, and 35 +/- 10 nmol/g, respectively. These data provide further confirmation that the vitamin B-6 pools in skeletal muscle are resistant to depletion. They also demonstrate that in humans with constant body weight, vitamin B-6 supplementation is not associated with marked increases in vitamin B-6 in muscle.

Muscle glycogenolysis during differing intensities of weight-resistance exercise

Skeletal muscle glycogen metabolism was investigated in eight male subjects during and after six sets of 70% one repetition maximum (1 RM, I-70) and 35% 1 RM (I-35) intensity weight-resistance leg extension exercise. Total force application to the machine lever arm was determined via a strain gauge and computer interfaced system and was equated between trials. Compared with the I-70 trial, the I-35 trial was characterized by almost double the repetitions (13 +/- 1 vs. 6 +/- 0) and half the peak concentric torque for each repetition (12.4 +/- 0.5 vs. 24.2 +/- 1.0 Nm). After the sixth set, muscle glycogen degradation was similar between I-70 and I-35 trials (47.0 +/- 6.6 and 46.6 +/- 6.0 mmol/kg wet wt, respectively), as was muscle lactate accumulation (13.8 +/- 0.7 and 16.7 +/- 4.2 mmol/kg wet wt, respectively). After 2 h of passive recovery without caloric intake, muscle glycogen increased by 22.2 +/- 6.8 and 14.2 +/- 2.5 mmol/kg wet wt in the I-70 and I-35 trials, respectively. Optical absorbance measurement of periodic acid-Schiff-stained muscle sections after the 2 h of recovery revealed larger absorbance increases in fast-twitch than in slow-twitch fibers (0.119 +/- 0.024 and 0.055 +/- 0.024, P = 0.02). Data indicated that when external work was constant, the absolute amount of muscle glycogenolysis was the same regardless of the intensity of resistance exercise. Nevertheless the rate of glycogenolysis during the I-70 trial was approximately double that of the I-35 trial.

Effects of exercise mode on muscle glycogen restorage during repeated days of exercise

The purpose of this study was to examine differences in muscle glycogen storage during three successive days of running or cycling. In a crossover design, seven male subjects performed two 3-d trials of either running (trial R) or cycling (trial C) for 60 min at 75% VO2max. Biopsy samples were obtained before and after each day's exercise from the gastrocnemius (trial R) or vastus lateralis (trial C) muscle. Diets in the 2 d preceding and during each trial contained 5 g carbohydrate.kg-1.d-1 and 14,475 +/- 402 kJ.d-1. Mean pre-exercise glycogen content (mmol.kg-1 wet wt.) was significantly reduced in both trials on day 3 (103.4 +/- 6.0) when compared to day 1 and day 2 (119.9 +/- 6.8 and 116.4 +/- 5.7, respectively). Day 1 glycogen reduction was significantly greater in trial C (P less than 0.03), and glycogen restorage was greater (P less than 0.02) only in trial C between the 1st and 2nd d. On day 3, spectrophotometric analysis of PAS strains showed that pre-exercise glycogen content in either muscle group was significantly (P less than 0.01) less in Type I as compared to Type II fibers. This difference in fiber glycogen storage did not appear to be attributable to muscle damage as negligible leukocyte infiltration and low blood CK levels were obtained. No difference between modes were observed for CK values throughout the trials. These data suggest that the depressed glycogen storage before the 3rd d of exercise was due to the moderate carbohydrate intake.

Influence of carbohydrate dosage on exercise performance and glycogen metabolism

This study was undertaken to examine the effects of ingestion of carbohydrate (CHO) solutions of 0 (WP), 6 (CHO-6), 12 (CHO-12), and 18 g CHO/100 ml (CHO-18) on performance and muscle glycogen use. Ten trained cyclists performed five 120-min cycling trials. The first 105 min of each trial was at 70% of maximal O2 consumption (VO2max), and the final 15 min was an all-out performance ride on an isokinetic cycle ergometer equipped to measure total work output. In one of the trials (CHO-12I) the submaximal portion of the ride consisted of seven 15-min rides at 70% of VO2max with a 3-min rest between each ride. Every 15 min the men consumed 8.5 ml.kg-1.h-1 (approximately 150 ml) of one of the four test solutions. Venous blood samples were obtained every 15 min for glucose and insulin. Muscle biopsies were obtained from the vastus lateralis at 0 and 105 min in the WP and the CHO-12 continuous and intermittent trials. Biopsy samples were assayed for glycogen and sectioned and stained for myosin adenosinetriphosphatase and glycogen for single fiber depletion measurements. There were no differences in glycogen use (86.7 +/- 6.0, 75.5 +/- 7.9, and 83.5 +/- 5.5 mmol/kg for the WP, CHO-12C, and CHO-12I, respectively) or depletion patterns between the WP and the two CHO-12 trials. Blood glucose was significantly elevated in both the CHO-12 trials and in the CHO-18 trial compared with the WP trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired muscle glycogen storage after muscle biopsy

To assess the effects of repeated needle biopsies on the rate of muscle glycogen repletion, eight male subjects were studied immediately after and 2 days after an exhaustive cycling bout. A single biopsy was obtained from the right vastus lateralis muscle immediately after an exhaustive cycling bout. Two days later, a sample was taken 1 cm lateral or medial to sample A. In four of these subjects, additional biopsies were taken 3 cm distal and proximal. A control specimen was also taken from the left leg 2 days after the exercise. Ten days after the exercise, muscle was again sampled from each leg of these four subjects. Analysis of these samples revealed that the initial biopsy impaired glycogen storage in the muscle taken 1 cm medial or lateral to the previous site. This reduction in glycogen storage was most pronounced in the first 2 days after the exercise. Samples taken distal and proximal to the initial biopsy contained, on the average, less glycogen than the contralateral leg, but these differences were only significantly different in the distal muscle sample. Alteration in muscle glycogen storage was seen to persist for 10 days after the first biopsy, suggesting that care must be taken in selecting the site for repeated biopsies from the same muscle.

Isokinetic rehabilitation after surgery. A review of factors which are important for developing physiotherapeutic techniques after knee surgery

The postoperative rehabilitation of individuals who've had surgery has been a primary concern of all members of the health care community. With the advent of new training devices for use during the rehabilitation period (i.e., isokinetic training devices) and new research in sports medicine, there has been a renewed interest in how to best rehabilitate individuals following surgery (knee surgery, in particular). This paper briefly reviews basic muscle physiology as it relates to muscle fiber types and recruitment patterns. Subsequently, it reviews studies that have investigated muscle atrophy and methods to reduce muscle dysfunction related to surgery, immobilization, and disuse. Finally, it reviews isokinetic training studies and examines the concept of "specificity of speed" training. These principles of muscle physiology and muscle plasticity are then applied to a proposed isokinetic rehabilitation program which might be adapted for use following joint surgery.

The WISC-R subtest profile of a sample of severely emotionally disturbed children

The WISC-R subtest profiles of 113 children classified as severely emotionally disturbed (88 males and 25 females; 71 Caucasians and 42 Negroes) ranging in age from 6 yr., 11 mo. to 13 yr., 8 mo. was examined. Diagnosis was based on psychological testing and quantitative assessment of behavioral deviations by parents, teachers, and psychologists. Scores for Caucasian children were significantly superior to those of Negro children, on the Information, Similarities, Vocabulary, and Picture Arrangement subtests. However, all subtest means foe both races were significantly lower than those in the standardization sample. A multivariate test of interaction and a Hotelling T2 suggested that the profiles of Caucasian and Negro subjects were not “flat” as those in the standardization sample and also not parallel. Investigation of the shape of the profiles of the races showed an elevated Picture Completion score for the Negro children and a depressed Coding score for Caucasian children. No evidence supported a discrepancy between Verbal and Performance abilities.