Jocelyn Ross

Effect of modified aerobic training on movement energetics in polio survivors.

Given that individuals with disabilities may be unable to achieve maximal oxygen uptake in an exercise test and that maximal exercise testing may cause increased fatigue, pain, and muscle weakness, we examined the role of submaximal exercise testing and training based on objective as well as subjective parameters in polio survivors. Experimental (N = 7) and control subjects (N = 13) were tested before and after a 6-week period. The experimental subjects participated in a 6-week exercise training program for 30 to 40 minutes, three times a week. The program consisted of treadmill walking at 55% to 70% of age-predicted maximum heart rates; however, exercise intensity was modified to minimize discomfort/pain and fatigue. Neither objective nor subjective exercise responses were significantly different in the control group over the 6 weeks. No change was observed in cardiorespiratory conditioning in the experimental group. However, movement economy, which is related to the energy cost of walking, was significantly improved; and walking duration was significantly increased at the end of training. Modified aerobic training may have a role in enhancing endurance and reducing fatigue during activities of daily living in polio survivors.

Downhill walking induces rapid shallow breathing.

To examine the effect of downhill walking a form of negative work on ventilation, we studied the exercise responses of 13 healthy subjects during uphill and downhill walking on a treadmill. Each test lasted 16 min and the peak work rate was 5.6 kph with either a positive or negative 14% grade. Throughout each test we recorded VO2, VE, f, VT, HR, systolic BP and Borgs rating of perceived exertion. At the target work rates of 5.6 kph ± 14% grade, VO2 and VE were three times greater in uphill compared with downhill walking. However, in downhill walking, f was greater compared with uphill walking wherein VT approximated baseline values, reflecting rapid shallow breathing, and VT appeared to increase after reaching some critically-low level. These trends persisted when VO2 was held constant (p<0.01). HR and systolic BP increased and decreased with the positive and negative grade respectively. At a constant VO2 however, HR was significantly higher during downhill compared with horizontal walking (p<0.01) whereas systolic BP was not significantly different (p>0.05). We conclude that there is a significant difference in the ventilatory responses between the two types of work performed on a treadmill. Specifically, downhill walking is associated with rapid shallow breathing which may be countered by a protective feedback mechanism at critically-low levels of VT.

Movement energetics of individuals with a history of poliomyelitis

Principles for evaluating the functional capacity of, and, therefore, exercise testing, chronically-disabled populations such as individuals with a history of poliomyelitis are considerably less well established than those for able-bodied persons. Therefore, we examined the use of indexes of movement economy and cardiorespiratory conditioning based on the results of a submaximal exercise test and oxygen consumption studies in individuals with a history of poliomyelitis. Subjects (n = 48) were categorized into four distinct groups, ie, having normal movement economy and either normal (n = 12) or reduced cardiorespiratory conditioning (n = 11), or having reduced movement economy and either normal (n = 10) or reduced cardiorespiratory conditioning (n = 15). There was no relationship between the indexes of movement economy and cardiorespiratory conditioning (p > 0.05) supporting that these indexes reflected physiologically-distinct entities. Irrespective of movement economy, deconditioned subjects had a reduced forced vital capacity (% predicted) (p < 0.05) and a higher resting heart rate (HR) (p < 0.01) compared to conditioned subjects. The difference in resting HR was attributed to conditioning level rather than initial arousal because resting HR and VO2 were comparable on repeated tests (p > 0.05). Although there was no difference in steady-state HR (% predicted maximum) among the four groups (p > 0.05), VO2 (% pred max) was significantly lower for the deconditioned than the conditioned subjects (p < 0.01). We concluded that determining movement economy and cardiorespiratory conditioning with a submaximal exercise test may enhance assessment and treatment outcome evaluation, hence provide a rational basis for rehabilitation interventions in individuals with a history of poliomyelitis.