Richard A. Shaffer

The purpose of this prospective study was to determine whether an association exists between foot structure and the development of musculoskeletal overuse injuries. The study group was a well-defined cohort of 449 trainees at the Naval Special Warfare Training Center in Coronado, California. Before beginning training, measurements were made of ankle motion, subtalar motion, and the static (standing) and dynamic (walking) characteristics of the foot arch. The subjects were tracked prospectively for injuries throughout training. We identified risk factors that predispose people to lower extremity overuse injuries. These risk factors include dynamic pes planus, pes cavus, restricted ankle dorsiflexion, and increased hindfoot inversion, all of which are subject to intervention and possible correction.

Development of techniques for the continuous measurement of regional blood flow and vascular resistance in intact small animals has been impeded primarily by the bulkiness of flow probes. The availability of an ultrasonic pulsed Doppler flowmeter system enabled us to construct miniaturized probes using 1-mm-diameter piezoelectric crystals that emit a 20-mHz signal and receive the reflected sound waves from passing blood cells. The finished flow probe is approximately 2.5-4 mm long and 2 mm in cross-sectional diameter with lumen diameters appropriate for the rat, ranging from 0.7 to 1.2 mm. This report describes the materials and methods involved in constructing and implanting the probes in rats to monitor renal, mesenteric, and hindquarter blood flow velocity. The accuracy of the pulsed Doppler method in detecting changes in regional blood flow and vascular resistance was established by the demonstration of a highly significant correlation between velocity recorded from the Doppler unit and volume flow recorded simultaneously. These data indicate that the ultrasonic pulsed Doppler flowmeter provides the opportunity to measure changes in regional blood flow and vascular resistance in a conscious freely moving rat.

PURPOSE: The purpose of this study was to identify rates of diagnosis-specific musculoskeletal injuries in U.S. Marine Corps recruits and to examine the association between patterns of physical training and these injuries. METHODS: Subjects were 1,296 randomly selected male Marine recruits, ages 17 to 28 yr, who reported to Marine Corps Recruit Depot San Diego for boot camp training between January 12 and September 14, 1993. Recruits were followed prospectively through 12 wk of training for injury outcomes. Injury patterns were examined in relation to weekly volumes and types of vigorous physical training. RESULTS: The overall injury rate was 39.6% (number of recruits injured/population at risk), with 82% of injuries occurring in the lower extremities. Overuse injuries accounted for 78% of the diagnoses. The most frequent site of injury was the ankle/foot region (34.3% of injuries), followed by the knee (28.1%). Ankle sprains (6.2%, N = 1,143), iliotibial band syndrome (5.3%, N = 1,143), and stress fractures (4.0%, N = 1,296) were the most common diagnoses. Injury rates were highest during the weeks with high total volumes of vigorous physical training and the most hours of running and marching. Weekly injury rates were significantly correlated with hours of vigorous physical training (overuse injuries r = 0.667, P = 0.018; acute injuries r = 0.633, P = 0.027). CONCLUSIONS: The results of this controlled epidemiological investigation indicate that volume of vigorous physical training may be an etiologic factor for exercise-related injuries. The findings also suggest that type of training, particularly running, and abrupt increases in training volume may further contribute to injury risk.

OBJECTIVE: Recent advances in understanding the neuroendocrine pathways regulating appetite, metabolism and body weight afford an opportunity to explore further the mechanisms by which obesity influences arterial pressure. ob/ob(Lep(ob)/Lep(ob)) mice have a mutation in the ob gene and are leptin-deficient. Leptin possesses pressor actions and has been shown to increase arterial pressure when infused chronically or over-expressed transgenically. In contrast, agouti yellow obese(Ay) mice have overexpression of an agouti peptide that blocks melanocortin receptors. Stimulation of melanocortin receptors by alpha-melanocyte-stimulating hormone decreases arterial pressure. DESIGN AND METHODS: This study measured arterial pressure in leptin-deficient ob/ob mice, agouti yellow obese mice and their lean controls to test the hypothesis that the effects of obesity on arterial pressure are importantly influenced by the genetic and neuroendocrine mechanisms causing the obesity. We measured arterial pressure directly in conscious ob/ob mice (n = 14), agouti yellow obese mice (n = 6) and the same number of lean littermates. RESULTS: Body weight was nearly twice as high in ob/ob mice as in their lean controls, but mean arterial pressure was significantly lower in ob/ob mice (92+/-3 mmHg) compared with their lean controls (106+/-2 mmHg; P = 0.00017). In contrast, mean arterial pressure was significantly higher in agouti yellow obese mice (124+/-3 mmHg) than in their lean controls (99+/-1 mmHg; P = 0.000002) despite the fact that the agouti mice had milder obesity. CONCLUSIONS: This study prompts three conclusions: (1) leptin-deficient ob/ob mice and agouti yellow obese mice have contrasting blood pressure responses to obesity, (2) obesity does not invariably increase arterial pressure in mice, and (3) the arterial pressure response to obesity may depend critically on the underlying genetic and neuroendocrine mechanisms.