Physical Training in Middle-Aged Men

Previous aerobic endurance studies have suggested that middle-aged groups have a reduced magnitude of physiological training response in comparison to their young adult counterparts. However, this observation is based on only a few studies involving middle-aged groups, often with a less demanding program of training compared to their younger counterparts. The purpose of this study was to examine the physiological effects of a comparatively strenuous program of aerobic endurance training in a group of middle-aged men. Physiological assessments were performed prior to (T1), after 15 weeks (T2) and 30 weeks (T3) training. VO max was assessed directly by means of a continuous graded bicycle ergometer test to exhaustion. This test also permitted the measurement of hemodynamic function by radionuclide ventriculography. The plasma lactate response to bicycle ergometer exercise was also assessed In order to assess any training specifity effect a submaximal treadmill exercise test was also performed. Body composition was assessed by total body weight, limb circumferences and body fat content. Body fat was determined using the skinfold and densitometric methods. Four skinfold sites were assessed: biceps, triceps, subscapular and supra-ilac. The training program consisted of a graded 30 week program of running training leading to participtaion in the 1984 City of Glasgow Marathon. Training prescription was based on exercise session frequency an duration. The intensity of training, although not prescribed, was sampled in some subjects during the study. The energy cost of training was predicted from subject training diaries using the speed and duration of their running during each training session. 216 telephone responses were obtained to a newspaper article advertising the study. After selection and medical/physical activity screening, 53 sedentary males aged 35 to 50 yrs. (40,0+/-4.3 yrs. ) were considered acceptable. Over the 30 weeks of training, 14 (26%) of the subjects dropped out. The main reason for drop-out was lack of time and loss of interest. The results of the present study are based on the 39 subjects who completed the 30 weeks training. VO2 max increased significantly (P <0.001) over the first 15 weeks training from 33.9+/- 4.0 ml/kg/min (T1) to 39.0+/- 5.6 ml/kg/min (T2). No significant change in VO. max was observed between T2 and T3 (38. 8 +/- 5.2 ml/kg/min) . This increase in VO max was the result of an increase in maximal cardiac output (T1-T3: 18.4+/-4.0 to 22. 0+/- 3.1 1/min) as the value of maximal arteriovenous oxygen difference did not significantly change (T1-T3: 14.4+/- 2.4 to 14.0+/- 1.9 ml/100ml). Maximal stroke volume increased with training while maximal heart rate fell (T1-T3: 103+/- 25 to 127+/- 16 me an +/- standard deviation ml; 179+/- 12 to 173+/- 11 beats/min). Submaximal treadmill and bicyle ergometer heart rate, oxygen uptake and pulmonary ventilation were all significantly reduced during the period of the present training study. A training specifity effect was suggested in this study as the magnitude of reduction in these submaximal parameters during treadmill exercise exceeded that of bicycle ergometer exercise. Submaximal bicycle ergometer plasma lactate concentration was reduced during the initial 15 weeks training, although this pattern of change was reversed from T2 to T3 with an increase in submaximal lactate concentration increased from T2 to T3 (OBLA Watts126+/- 30 to 152+/- 28 to 132+/- 34 Watts). The factors potentially responsible for this reversal in submaximal plasma lactate response are discussed in the text. Total body weight and the sum of skinfolds significantly fell (P < 0.001) during both the first and second 15 weeks of training (799 + 10.1 to 77.2+/- 10.7 to 75.4+/- 11.1 kg and 56.0+/- 11.8 mm to 48.1+/- 11.1 to 48.1+/- 11.1 mm). Body density increased (1.047 to 1.053 to 1.058 kg/m x 10) over the period of training resulting in a reduction in total body fat content (22.7+/- 3.7 to 20.0+/- 4.0 to 17.4+/- 7.4 %) . The energy cost of training exceeded the energy value associated with the loss in body fat suggesting a reduction in energy intake over the period of the study (T1-T3: +47751+/- 250521 kcal/min). The relative magnitude of this increase in VO max (15%) observed during the period of the present study is no greater than reported by previous studies involving less strenuous training programs. The results of submaximal treadmill testing suggest that this failure to increase VO2max in excess of previous studies is probably reflective of training specifity rather than aging per se. In agreement with previous studies investigating middle-aged groups, the heamodynamic results of this study suggest that the factors responsible for increasing VO2max are central rather than peripheral. The reductions in total body weight and body fat content observed over the period of the present study are considerably greater than those typically reported by previous studies involving both middle-aged and young adult groups. In conclusion, the middle-aged subjects in the present study achieved a similar magnitude of cardiorespiratory adaption with training to that reported in previous young adult studies. However, in support of the hypothesis that training adaptability is reduced with aging, the present training program is more physically demanding than previous studies involving both young and older subjects