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.

Fifteen-year interval spirometric evaluation of the Oregon predictive equations.

The 1969 Oregon spirometric predictive equations were evaluated by retesting 199 of the 988 original sample population after 15 years. The 1969 data were used to test for sample bias between the retested and not-retested groups. There was no significant difference in mean values for age, height, or test results except for a five-year age difference in men. Regression analysis of residuals and the differences between calculated and predicted values of annual decrements of FVC, FEV1, and FEF25-75% on age revealed no statistically significant age trend. Although residual means were statistically significant for FVC and FEV1 for men and FVC and FEF25-75% for women, the differences between calculated and predicted annual decrements were significant only for women in FEF25-75%. Although group performance was accurately predicted for most tests, test SDs and SEMs demonstrated considerable individual variation. Lower limits of normality are suggested to assist in evaluating previously-tested patients.

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.

Limitations to exercise capacity and endurance: pulmonary system.

The response of the pulmonary system to exercise is well-documented to be quite precise in its homeostatic regulation, highly efficient in terms of its physiologic cost, and operating well within its maximum reserves. Two exceptions to these generalizations are documented here in the highly-trained athlete: 1) the arterial hypoxemia observed in short-term work at a VO2 greater than 4-5 l . min-1, and 2) the tachypneic hyperventilation of long-term, heavy exercise in varying environmental conditions. The potential causes and consequences of these responses are discussed with reference to so-called exercise "limitations". The trained state as a cause of pulmonary limitations is emphasized.

Determinants and consequences of ventilatory responses to competitive endurance running.

Pulmonary ventilation and pattern, arterial blood gases, and [H+] were studied in 15 highly trained runners [maximum O2 consumption (VO2 max) 53--82 ml . kg-1 . min-1] during road racing (24 km, n = 5) and 60--70 min of treadmill running (70--75% VO2 max, n = 13). The predominant response throughout prolonged treadmill running and especially road running was a tachypneic, respiratory alkalosis (-5 to -12 Torr PaCO2) that was evident early in the exercise. Time-dependent increases in breathing frequency (10--40%, 6--60 min work), expired ventilation, and dead space ventilation were common in prolonged work; these were especially evident in two subjects even as VO2 fell during road racing under hot humid conditions. The tachypneic hyperventilation was 1) most often accompanied by alkaline [H+]a, 2) associated with time-dependent elevation in rectal temperature (1--1.5 degrees C) and circulating norepinephrine (5--20 x rest), 3) quickly alleviated via hyperoxia after 60--70 min of exercise, and 4) was shown to result from increased running velocity in separate experiments that compared walking vs. running at similar CO2 excretion and [HCO-3]a. In highly trained runners competing under favorable environmental conditions and optional pace selection, we view the net effects of the hyperventilatory response to be truly advantageous, whereby the benefits to pulmonary gas exchange and [H+] regulation outweigh the expense of some inefficiency in ventilatory work and pattern and a departure from steady-state homeostasis.

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.