PHYSIOLOGICAL AND SPINAL-RESPONSES TO CIRCUIT WEIGHT-TRAINING

Physiological, perceptual and physical responses to a typical circuit weight-training (CWT) regimen were recorded in two studies. The aims were to assess the intensity of exercise during CWT; and to determine whether physical responses as evaluated by spinal shrinkage were related to physiological and perceptual responses to CWT. In the first study (n = 10) heart rate (HR), oxygen consumption (VO2), ventilation (VE), blood lactate (La) and perceived exertion (RPE) were measured in response to CWT. Mean (+/- SD) time to complete three circuits of CWT was 17.8 (+/- 1.4) min. The HR max, VO2 max and peak La, measured first during an incremental treadmill test, were 195 (+/- 13) beats.min-1, 59.7 (+/- 4.8) ml.kg-1.min-1 and 14.3 (+/- 3.5) mM respectively. Mean HR and VO2 during CWT were 69% and 50% of the respective maximal values. The HR-VO2 ratio observed on the treadmill was elevated during CWT, with VO2 being lowered relative to HR. Mean VE and La values were 52-7 (+/- 14.5) l.min-1 and 6.9 (+/- 3.6) mM. The effect of the same CWT regimen on spinal loading as indicated by change in stature (shrinkage) was investigated in a second study (n = 8). The mean (+/- SD) time taken to complete the circuit was 17.4 (+/- 1.3) min. Mean shrinkage due to CWT (2.5 +/- 1.5 mm) was unrelated to the time taken to complete the circuits, to HR, RPE or to low back pain ratings (p > 0.05). Observations suggest that CWT as represented in these studies engages anaerobic as well as aerobic mechanisms but the exercise intensity may not provide sufficient stimulation for aerobic training. The physical load on the spine indicated by spinal shrinkage was not related to the physiological or perceptual strain.