EXERCISE TRAINING BELOW AND ABOVE THE LACTATE THRESHOLD IN THE ELDERLY

In this study we report the effects of training at intensities below and above the lactate threshold on parameters of aerobic function in elderly subjects (age range 65-75 yr). The subjects were randomized into high-intensity (HI, N = 8; 75% of heart rate reserve = approximately 82% VO2max = approximately 121% of lactate threshold) and low-intensity (LI, N = 9; 35% of heart rate reserve = approximately 53% VO2max = approximately 72% of lactate threshold) training groups which trained 4 d.wk-1 for 30 min.session-1 for 8 wk. Before and after the training, subjects performed an incremental exercise test for determination of maximal aerobic power (VO2max) and lactate threshold (LT). In addition, the subjects performed a 6-min single-stage exercise test at > 75% of pre-training VO2max (SST-High) during which cardiorespiratory responses were evaluated each minute of the test. After training, the improvements in VO2max (7%) for LI and HI were not different from one another (DELTA-VO2max for LI = 1.8 +/- 0.7 ml.kg-1. min-1; DELTA-VO2max for HI = 1.8 +/- 1.0 ml.kg-1.min-1) but were significantly greater (P = 0.02) than the post-testing change observed in the control group (N = 8). Training improved the LT significantly (10-12%; P < 0.01) and equally for both LI and HI (DELTA-LT for LI = 2.3 +/- 0.6 ml O2.kg-1.min-1; DELTA-LT for HI = 1.8 +/- 0.8 ml O2.kg-1.min-1). In comparison with controls, during the post-training SST-High for LI and HI, there were significant training-induced reductions in the exercise heart rate, V(E), and VCO2. These results demonstrate that, for previously sedentary elderly subjects, 8 wk of low-intensity training (i.e., below the LT) provide comparable increases in VO2max and LT and decreases in cardiorespiratory responses to high-intensity exercise, as compared with 8 wk of high-intensity training (i.e., above the LT). We conclude that low-intensity, sub-LT walking training (as defined herein) is an adequate aerobic training stimulus for producing modest gains in aerobic power in previously sedentary elderly subjects.