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Biomedical subjects

W M Sherman

Publications and source records attributed to W M Sherman.

64 records · Page 4Linked to original sources
PubMed1983

Endurance improved by ingestion of a glucose polymer supplement.

The effect of glucose polymer (GP) ingestion upon endurance performance during walking exercise at 45% VO2max was examined. Also, performance on a battery of psychomotor tests was assessed to determine if exhaustion from endurance exercise was related to central nervous system dysfunction. Ten trained male subjects ingested approximately 120 g of GP in four equally-divided dosages 60, 90, 120, and 150 min following the start of exercise. This treatment significantly increased time to exhaustion by 11.5% as compared to the control (C) group (GP=299.0 +/- 9.8 min; C=268.3 +/- 11.8 min). No difference in VO2 (1 X min-1) or perceived exertion was noted between treatments. As a result of the GP feedings the rate of carbohydrate utilization during the GP trial was 0.53 g X min-1 greater than during the C trial. However, during the GP trial plasma glucose did not fall below the pre-exercise level and was significantly higher than the C plasma glucose concentration at exhaustion. No differences in psychomotor performance between treatments or between rested and exhausted states for either the C or GP treatments were noted. These data suggest that exhaustion was not a result of hypoglycemia or central nervous system dysfunction and that glucose polymer supplements may enhance endurance capacity.

Blood Glucose↗
PubMed1982

Muscle glycogen storage and its relationship with water.

This study examined the relationship between muscle glycogen and muscle water content. Exercise dietary manipulations were used to vary skeletal muscle glycogen levels in four groups of rodents: (1) eight animals were sedentary controls (SC); (2) ten animals were treadmill familiarized and allowed to recover 24 h before sacrifice (F); (3) ten animals were treadmill familiarized and exercised to exhaustion (E); (4) ten animals were treadmill familiarized, exercised to exhaustion, and allowed to recover with food and water ad libitum for 72 h (ER). All animals were sacrificed in a resting state to normalize intracellular, extracellular, and interstitial water compartments; thus, the E group was sacrificed 45 m in following their run. The treatments altered skeletal muscle glycogen to values ranging from 10.0 to 30.2 mumol glucosyl units/g wet tissue weight. Neither muscle triglyceride nor protein levels were affected by the treatments. Muscle water content expressed as mumol H2O lost/g wet tissue weight or made relative to protein content showed no consistent relationship to the glycogen content. These data, therefore, do not support the commonly accepted muscle glycogen-to-water ratio of 1.0:2.7 (g:g). Further work is necessary to quantify the exact amount of water that is actually associated with the glycogen complex.

Animals↗
PubMed1982

Relationship between muscle QO2 and fatigue during repeated isokinetic contractions.

The percent slow-twitch fibers (%ST) of the vastus lateralis muscle and selected indicators of maximum aerobic power (QO2, VO2 max, and leg extensor VO2 max) were compared with the rate of fatigue development during 45 s of repeated maximum isokinetic leg extension-flexion contractions (180 degrees/s) on 13 males. Subjects with muscle respiratory capacities (QO2) above the mean (2,472 microliter O2 X h-1 X g-1) displayed a significantly slower rate of fatigue development than those subjects with QO2 values below the mean. In addition, indicators of maximum aerobic power were correlated with the percent of maximum power and power/ml fat-free thigh volume at 5, 15, 30, and 45 s during the fatigue test. The correlations increased progressively during the fatigue test and became significant at 45 s. This trend was not observed when the %ST fibers were compared with the percent of maximum power and power/ml fat-free thigh volume at these time intervals. These data suggest that 1) the muscle tissue's capacity for aerobic metabolism influences the rate of fatigue development even during a strenuous short-term isokinetic exercise task, and 2) factors other than fiber type may interact to confound the prediction of fiber type by noninvasive means.

Adolescent↗
PubMed1981

Specificity of the anaerobic threshold in endurance trained cyclists and runners.

This study examined the specificity of maximum aerobic power and the anaerobic threshold (AT) in 10 endurance-trained cyclists and 10 endurance-trained runners who performed continuous progressive work tests on the bicycle ergometer and treadmill. Dependent 't' tests for VO2max l/min-1 indicated that the cyclists scored higher on the bicycle ergometer (X = 4.5 l/min-1) than the treadmill (X = 4.34 l/min-1) but the difference was not statistically significant. By contrast, the runners fared significantly better (p less than 0.05) on the treadmill (X = 68.1 ml/kg . min-1) compared with the bicycle ergometer (X = 61.7 ml/kg . min-1). When the AT was expressed as a percentage of VO2max, there were no significant differences between the cyclists (66.3%) and runners (61.2%) on the bicycle ergometer or the runners (77.3%) and cyclists (74.3%) on the treadmill. However, this tendency for the better score to be registered by the group tested on the activity for which it trained was most pronounced when the AT was expressed in l/min-1 and ml/kg . min-1. Independent 't' tests accordingly indicated that the cyclists (3.0 l/min-1) had significantly (p less than 0.05) greater AT's than the runners (2.56 l/min-1) on the bicycle ergometer whereas the runners (52.7 ml/kg . min-1) had significantly (p less than 0.05) higher AT's than the cyclists (46.8 ml/kg . min-1) on the treadmill. These data suggest that the adaptive responses to exercise are in part a function of the specific movement patterns executed in training. Thus, if VO2max and the AT are to be measured in the laboratory, the tests must allow optimal innervation of the specifically trained muscle fibres.

Adult↗
PubMed1981

Effect of exercise-diet manipulation on muscle glycogen and its subsequent utilization during performance.

This study examined the effect of three exercise-diet regimens on muscle glycogen supercompensation and subsequent performance during a 20.9-km run. A diet containing 15% carbohydrate (CHO,L), 50% CHO (M), or 70% (CHO (H) was arranged in three trials as follows: trial A = 3 days L, 3 days H; trial B = 3 days M, 3 days H; trial C = 6 days M. For each trial a 5-day depletion-taper exercise sequence was conducted on the treadmill at 73% VO2 max. The runs were 90, 40, 40, 20, and 20 min, respectively. A day of rest preceded the 20.9-km performance run. Muscle biopsies were obtained from the gastrocnemius on days 4 and 7 (both prior to and after the performance run). Trials A, B, and C elevated muscle glycogen to 207, 203, and 159 mmol glucosyl units/kg wet tissue (mmG), respectively. The performance run in both trials A and B utilized significantly more glycogen than in trial C: 5.0 and 5.1 mmG/km vs. 3.1 mmG/km. There were, however, no differences in either performance run times or post-performance run glycogen levels between the trials. These data demonstrate that (1) muscle glycogen can be elevated to high levels with a moderate exercise-diet regimen; (2) initial muscle glycogen levels influence the amount subsequently utilized during exercise; (3) carbohydrate loading is of no benefit to performance for trained runners during a 20.9-km run.

Adult↗
PubMed1981

The role of dietary carbohydrates in muscle glycogen resynthesis after strenuous running.

This study examined the effect of the type, amount, and the frequency of feeding of carbohydrates on muscle glycogen resynthesis after running. Trained male runners performed a 16.1 km run at 80% VO2 max to decrease gastrocnemius glycogen levels. A complex or simple carbohydrate diet (approximately 3000 kcal) resulted in similar muscle glycogen levels 24 h after exercise. Forty-eight hours after exercise the complex carbohydrate diet resulted in significantly higher (p less than 0.05) muscle glycogen levels. Consuming increasing amounts of carbohydrate, between 88 to 648 g carbohydrate/day, resulted in increasingly larger amounts of muscle glycogen resynthesis (24 h) after exercise. Frequent feedings of a high carbohydrate diet did not enhance muscle glycogen synthesis when compared to equal amounts of carbohydrates in two meals. It appears that muscle glycogen can be normalized between daily strenuous running activity.

Adult↗
PubMedDate not supplied

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.

Atrophy↗
PubMedDate not supplied

The marathon: dietary manipulation to optimize performance.

Despite pronounced involvement of the cardiovascular and respiratory systems during the marathon, the limiting factor for this event revolves around the supply and utilization of intramuscular and extramuscular fuel reserves. The single most consistently observed factor contributing to fatigue at work intensities selected by marathon runners is the depletion of muscle's endogenous carbohydrate, glycogen. Dietary manipulations which reduce the rate of muscle glycogen degradation will, therefore, spare this important fuel and delay fatigue. The purpose of this paper will be to review dietary factors which are pertinent to fuel utilization in order to optimize marathon performance.

Dietary Carbohydrates↗
PubMedDate not supplied

Aerobic training and diabetic nephropathy in the obese Zucker rat.

The effects of aerobic exercise training on diabetes control and the development of renal microvascular disease were studied in the obese Zucker rat, an animal model of noninsulin dependent diabetes mellitus (NIDDM). Training consisted of 12 weeks of treadmill running, beginning at six weeks of age. Eight trained obese Zucker rats were compared to 15 obese sedentary controls and to 22 sedentary lean nondiseased littermates. Fasting blood glucose, percent of glycated hemoglobin, serum insulin, serum total cholesterol, body weight and kidney weight, creatinine clearance, urine total protein excretion, urine albumin excretion, and morphometric analyses of cortical glomeruli by light and electron microscopy were performed to evaluate metabolic control, renal function, and structure. Training was associated with less albuminuria, less mesangial volume expansion, and less glomerular basement membrane thickening compared to obese sedentary NIDDM animals. These results suggest that exercise training reduces the glomerular ultrastructural lesions and attenuates the albumin excretion rate in this rat model of obesity-related diabetes.

Aerobiosis↗