Elisabeth Spector

Resistance exercise training and the orthostatic response

Abstract Resistance exercise has been suggested to increase blood volume, increase the sensitivity of the carotid baroreceptor cardiac reflex response (BARO), and decrease leg compliance, all factors that are expected to improve orthostatic tolerance. To further test these hypotheses, cardiovascular responses to standing and to pre-syncopal limited lower body negative pressure (LBNP) were measured in two groups of sedentary men before and after a 12-week period of either exercise (n = 10) or no exercise (control, n = 9). Resistance exercise training consisted of nine isotonic exercises, four sets of each, 3 days per week, stressing all major muscle groups. After exercise training, leg muscle volumes increased (P < 0.05) by 4–14%, lean body mass increased (P = 0.00) by 2.0 (0.5) kg, leg compliance and BARO were not significantly altered, and the maximal LBNP tolerated without pre-syncope was not significantly different. Supine resting heart rate was reduced (P = 0.03) without attenuating the heart rate or blood pressure responses during the stand test or LBNP. Also, blood volume (125I and 51Cr) and red cell mass were increased (P < 0.02) by 2.8% and 3.9%, respectively. These findings indicate that intense resistance exercise increases blood volume but does not consistently improve orthostatic tolerance.

Bone Loss in Space Flight and Countermeasures

Before manned space flight, it was known that immobilization of patients for extended periods, such as for fracture repair to treat the paralysis of polio myelitis or paraplegia, often resulted in weakened and atrophic bones. Although the problems related to reduced gravitational forces on the musculoskeletal system were recognized, the full extent of the changes was not known. Therefore, studies were planned and conducted by the emerging American and Soviet space programs to determine the extent of, and potential harm associated with, bone loss that might occur during space flight.