Effects of extremity loading upon energy expenditure and running mechanics.

Physiological and mechanical consequences of running with commercially available hand and/or ankle weights were examined. Five males and three females (age 30 to 56 yr) ran for 30 min on a treadmill (0% grade) at a self-selected pace (8.9 to 13.7 km.h-1), under randomized conditions of: (i) unloaded weights; (ii) hand weights; (iii) ankle weights; and (iv) hand + ankle weights. Respiratory gas exchange determinations, heart rates, and sagittal view film clips were obtained at selected time intervals. Highest energy expenditures and heart values were obtained for the fully loaded condition, with intermediate values measured for independent hand- and ankle-weighted trials. Increased energy expenditure due to loading ranged from 5 to 8%. Lower extremity kinematics were unaffected by loading. Angular velocity and excursion of the arm segments was significantly (P less than 0.05) reduced when hand weights alone were carried. The results indicate that commercial claims of marked increases in energy expenditure during running with hand/ankle weights are exaggerated. It appears that the small actual increases in energy expenditure, the potential for increased impact forces, and the relative discomfort of carrying weights discredit running with hand and/or ankle weights as a desirable exercise alternative.

The Ability of Instructors to Organize Aerobic Dance Exercise Into Effective Cardiovascular Training.

In brief: The ability of five aerobics instructors to combine music and exercise movements into effective cardiovascular training was evaluated at Oregon State University in Corvallis. Respiratory gas exchange and heart rate determinations were made during dance exercise sequences that were estimated to represent low, medium, and high levels of exercise intensity. Besides the instructors, twelve subjects (ten women and two men) participated in the study. The results showed that the instructors tended to create exercise routines at lower and upper intensity levels (the latter having a higher risk of injury). This tendency accentuates the need for responsible accreditation of instructors.

A model treadmill adaptation for wheelchair ergometry.

We have designed, constructed and tested a restraining apparatus to permit safe uninhibited hand propulsion of a wheelchair on a motor driven treadmill. The special design features of the tracking assembly minimize any potential hazard or apprehension associated with possible lateral or rearward displacement of a chair from the belt surface. Special linear bearings minimize any increase in rolling resistance (less than 1.23 X 10(-3) N force displacement) at speeds ranging from 4 to 282 m. min.-1. The supporting frame is adjustable for variations in treadmill belt widths and different model wheelchairs. Easy removal of the chair enables convenient conversion of the treadmill for walking/running activity.

Heat tolerance following diuretic induced dehydration.

In an effort to assess the effects of acute fluid loss on body temperature regulation during exercise, seven subjects (one female and six males) were studied on two occasions during two hours of cycling (35% Vo2max) in a hot environment (39 degrees C = DB, 35% = RH). One trial (D) was conducted following a 3% body weight reduction, achieved with 40-80 mg oral administration of a diuretic "lasix." A control exercise bout was performed with the subject normally hydrated (H). As a result of the diuresis, plasma volume (PV) decreased 15.3% (SE +/- 1.3), while heart rates during exercise increased 20-25 beats/min when compared to the H condition. Although significantly greater increases (P less than 0.05) in rectal and muscle temperatures occurred during exercise in the D trial, mean skin temperature (TS) was lower. Skin blood flow estimated from conductance values averaged 800 ml/min less during the D condition than during exercise in the H trial. Since the preliminary diuresis had no affect on sweat rate during exercise (D = 0.80 vs. H = 0.80 liters/hr), body heat dissipation appeared limited mainly by a reduction in peripheral blood flow. The diuretic induced dehydration was found to increase the sensitivity of some subjects to the exercise-heat stress, producing symptoms of heat exhaustion.

Comparison of metabolic, temperature, heart rate and ventilatory responses to exercise at extreme ambient temperatures (0 degrees and 35 degrees C.).

Eight male subjects exercised on a bicycle ergometer for one half to one hour at loads demanding 52 to 59% of Vo2max on two separate occasions, once with ambient temperature held at 0 degrees C and once in a 35 degrees C environment. Throughout exercise and during recovery in a 25 degrees C environment, measurements were made of oxygen consumption, ventilation, heart rate, muscle-rectal-skin temperatures, and blood lactic acid. In the hot condition significant increases in heart rate, blood lactates, sweat loss, muscle, rectal and skin temperature responses were observed. At 0 degrees C Vo2 was significantly elevated during exercise over that in the 35 degrees C condition. Despite the elevated Vo2 response in the cold, higher body temperatures measured in the heat were associated with a significantly higher (P less than .025) recovery Vo2 (x = 866 ml), which was of the magnitude predicted by the van't Hoff-Arrhenius relationship.