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Biomedical subjects

B H Jones

Publications and source records attributed to B H Jones.

69 records · Page 4Linked to original sources
PubMed1988

Prevention of lower extremity stress fractures: a controlled trial of a shock absorbent insole.

A prospective controlled trial was carried out to determine the usefulness of a viscoelastic polymer insole in prevention of stress fractures and stress reactions of the lower extremities. The subjects were 3,025 US Marine recruits who were followed for 12 weeks of training at Parris Island, South Carolina. Polymer and standard mesh insoles were systematically distributed in boots that were issued to members of odd and even numbered platoons. The most important finding was that an elastic polymer insole with good shock absorbency properties did not prevent stress reactions of bone during a 12-week period of vigorous physical training. To control for the confounding effects of running in running shoes, which occurred for about one and one-half hours per week for the first five weeks, we also examined the association of age of shoes and cost of shoes with injury incidence. A slight trend of increasing stress injuries by increasing age of shoes was observed. However, this trend did not account for the similarity of rates in the two insole groups. In addition, we observed a strong trend of decreasing stress injury rate by history of increasing physical activity, as well as a higher stress injury rate in White compared to Black recruits. The results of the trial were not altered after controlling for these factors. This prospective study confirms previous clinical reports of the association of stress fractures with physical activity history. The clinical application of a shock absorbing insole as a preventive for lower extremity stress reactions is not supported in these uniformly trained recruits. The findings are relevant to civilian populations.

Adolescent↗
PubMed1987

Influence of a 3.5 day fast on physical performance.

Eight young men were tested for strength, anaerobic capacity and aerobic endurance in a post absorptive state and after a 3.5 day fast. Strength was tested both isokinetically (elbow flexors, 0.52 rad x s-1 and 3.14 rad x s-1) and isometrically. Anaerobic capacity was evaluated by having subjects perform 50 rapidly repeated isokinetic contractions of the elbow flexors at 3.14 rad x s-1. Aerobic endurance was measured as time to volitional fatigue during a cycle ergometer exercise at 45% VO2max. Measures of VO2, VE, heart rate, and ratings of perceived exertion were obtained prior to and during the cycle exercise. The 3.5 day fast did not influence isometric strength, anaerobic capacity or aerobic endurance. Isokinetic strength was significantly reduced (approximately 10%) at both velocities. VO2, VE and perceived exertion were not affected by fasting. Fasting significantly increased heart rate during exercise but not at rest. It was concluded that there are minimal impairments in physical performance parameters measured here as a result of a 3.5 day fast.

Adult↗
PubMed1986

Metabolic changes following eccentric exercise in trained and untrained men.

The effects of one 45-min bout of high-intensity eccentric exercise (250 W) were studied in four male runners and five untrained men. Plasma creatine kinase (CK) activity in these runners was higher (P less than 0.001) than in the untrained men before exercise and peaked at 207 IU/ml 1 day after exercise, whereas in untrained men the maximum was 2,143 IU/ml 5 days after exercise. Plasma interleukin-1 (IL-1) in the trained men was also higher (P less than 0.001) than in the untrained men before exercise but did not significantly increase after exercise. In the untrained men, IL-1 was significantly elevated 3 h after exercise (P less than 0.001). In the untrained group only, 24-h urines were collected before and after exercise while the men consumed a meat-free diet. Urinary 3-methylhistidine/creatinine in the untrained group rose significantly from 127 mumol/g before exercise to 180 mumol/g 10 days after exercise. The results suggest that in untrained men eccentric exercise leads to a metabolic response indicative of delayed muscle damage. Regularly performed long distance running was associated with chronically elevated plasma IL-1 levels and serum CK activities without acute increases after an eccentric exercise bout.

Creatine Kinase↗
PubMedDate not supplied

Effects of high-fat diet, angiotensinogen (agt) gene inactivation, and targeted expression to adipose tissue on lipid metabolism and renal gene expression.

To address the role of angiotensinogen (agt) in lipid metabolism and its potential endocrine effects in vivo, we studied the effects of high-fat diet (HFD) on adult, 28-week-old agt knockout (KO) mice compared to wild type (WT) mice. Recent studies (Massiera et al., 2001) have demonstrated that reexpression of agt in adipose tissue of KO mice normalized adiposity, blood pressure, and kidney abnormalities. We therefore used microarray analysis to investigate changes in gene expression profile in kidneys of KO vs. Tg-KO mice, where agt expression is restricted to adipose tissue. Body weight, adiposity and insulin levels were significantly decreased (p < 0.05) in KO mice on a chow diet (CD) compared to WT mice, while circulating leptin levels were similar. On a high-fat diet, KO mice exhibited significantly lower bodyweight (p < 0.05), adiposity (p < 0.05), leptin, and insulin levels (p < 0.05) compared to WT mice. In agreement with previously reported changes in kidney histology, agt KO mice displayed altered expressions of genes involved in blood pressure regulation and renal function, but these levels were corrected by reexpression of agt in adipose tissue. Collectively, these findings further document important endocrine roles of adipocyte agt, in part via regulation of lipid metabolism and kidney homeostasis.

Adipose Tissue↗
PubMedDate not supplied

Effects of fatty (fa) allele and high-fat diet on adipose tissue leptin and lipid metabolism.

Leptin is an adipocyte-secreted hormone that binds hypothalamic receptors and potently decreases food intake. Leptin receptor defects in homozygous mutant Zucker fatty ( fa/fa) rats lead to massive obesity, hyperphagia, decreased energy expenditure, and insulin resistance, while the phenotype of heterozygous ( Fa/fa) lean rats lies between lean ( Fa/Fa) and obese ( fa/fa) rats. Whether heterezygotes exhibit specific changes in lipid metabolism in a diet-responsive manner is not clear. Thus, the specific aim of this study was to test whether the presence of one fa allele modulates lipid metabolism and leptin, and whether these effects are exacerbated by high-fat diet. We demonstrate that the presence of one fa allele significantly increases lipogenesis in adipose tissue assessed by glycerol-3-phosphate dehydrogenase (GPDH) and fatty acid synthase (FAS) activities. FAS is more responsive to high-fat diets than GPDH in Fa/fa rats. Adipose tissue leptin levels are significantly higher in fat pads of Fa/fa compared to Fa/Fa rats. Moreover, Fa/fa rats fed high-fat diet show an additional two-fold increase in leptin levels compared to wild type rats on the same diet. Collectively, these results indicate that the presence of one fa allele increase adipocyte lipogenic enzyme activities, which results in hyperleptinemia concurrent with increased adiposity.

Adipocytes↗
PubMedDate not supplied

Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes.

One hundred thirty-eight female collegiate athletes, participating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was measured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or competition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extremity injuries in female collegiate athletes.

Adolescent↗
PubMedDate not supplied

Intrinsic risk factors for exercise-related injuries among male and female army trainees.

Physical training-related injuries are common among army recruits and other vigorously active populations, but little is known about their causation. To identify intrinsic risk factors, we prospectively measured 391 army trainees. For 8 weeks of basic training, 124 men and 186 women (79.3%) were studied. They answered questionnaires on past activities and sports participation, and were measured for height, weight, and body fat percentage; 71% of the subjects took an initial army physical training test. Women had a significantly higher incidence of time-loss injuries than men, 44.6% compared with 29.0%. During training, more time-loss injuries occurred among the 50% of the men who were slower on the mile run, 29.0% versus 0.0%. Slower women were likewise at greater risk than faster ones, 38.2% versus 18.5%. Men with histories of inactivity and with higher body mass index were at greater injury risk than other men, as were the shortest women. We conclude that female gender and low aerobic fitness measured by run times are risk factors for training injuries in army trainees, and that other factors such as prior activity levels and stature may affect men and women differently.

Adult↗
PubMedDate not supplied

Validity of self-assessed physical fitness.

This study compared self-ratings of components of physical fitness with objective measures of physical fitness. We made comparisons in two groups of male infantry soldiers (n = 96 and n = 276) and one group of older male military officers (n = 241). To obtain self-ratings of physical fitness, we asked subjects, "Compared to others of your age and sex, how would you rate your (a) endurance, (b) sprint speed, (c) strength, (d) flexibility?" Subjects responded to each of the four questions on a five-point scale. Self-ratings of endurance were systematically related to three measures of aerobic capacity, including VO2max, peak VO2, and two-mile run time (r = 0.29 to 0.53). Self-ratings of sprint speed showed only weak relationships to measures of anaerobic capacity assessed by the Wingate test, push-ups, and sit-ups (r = 0.10 to 0.17). Strength ratings were systematically related to measures of maximal strength (r = 0.28 to 0.53). Upper body strength measures were more closely associated with the self-ratings of strength than were measures of lower body strength. Responses to the flexibility question were systematically related to measures of hip/low back flexibility (r = 0.30 and 0.48) but not to other measures of flexibility. Apparently, physically active subjects can approximately classify their aerobic capacity, muscle strength, and some types of flexibility.

Age Factors↗
PubMedDate not supplied

Cigarette smoking, physical fitness, and injuries in infantry soldiers.

Reliable data on the impact of physical training on light infantry units in terms of injuries and time loss are sparse. This study evaluated a light infantry unit (n = 181) prospectively and followed it throughout one year of infantry training and operations. Fifty-five percent of the soldiers (n = 101) experienced one or more injuries. Eighty-eight percent of the injuries were training-related conditions, which resulted in 1,103 days of limited duty. Lower extremity overuse injuries were the most common type of injury documented. Fractures accounted for the greatest number of days of limited duty. Risk factors for training-related injuries identified by this study were cigarette smoking, high percentage of body fat, extremely high or low body mass index, low endurance levels, and low muscular endurance levels (sit-ups). Logistic regression showed that cigarette smoking and low endurance levels were independent risk factors for training injuries. These data indicate that the incidence of training-related injuries in infantry units is high. A number of modifiable injury risk factors were identified, suggesting that many of these injuries may be preventable.

Adult↗