Abstract

Nine male marathon runners, 24 to 39 y, were studied during steady state and maximal graded treadmill exercise under control conditions (C) and immediately after a paced outdoor 21.1-km run averaging 89.5 min (E). The half-marathon run and both treadmill trials were performed at 239+/-33 m/min. VO2, respiratory exchange ratio (RER), heart rate (HR), plasma lactate concentration (PLa), and rating of perceived exertion (RPE) were measured in the steady state at 0 grade and at the fatigue end point. Compared to C, mean values in E were significantly lower for time to exhaustion (6.0 vs 4.1 min), VO2max (60.0 vs 56.3 ml/kg/min), peak RPR (1.18 vs 1.06), and PLa (9.7 vs 7.8 mM/L), whereas maximal HR (184 vs 184 b/min) and peak RPE (19.6 vs 19.9) were not significantly different between trials. Submaximal VO2 during steady-state runs was similar between C and E (44.4 vs 45.0 ml/kg/min; p = NS). Since the attainable VO2max decreased after E, the percentage of VO2max utilized during steady-state runs was higher, averaging 74 in C and 80 in E. In the steady state during E, HR (153 vs 161 b/min) and RPE (13.2 vs 14.8) were higher, and the increase in PLa from rest (2.7 vs 1.9 mM/L) was lower. Submaximal HR during graded exercise in E was 7 to 8 b/min higher at a given VO2, indicating reduced heart rate reserve. The results show that the peak attainable VO2max acutely decreased after the 21.1-km run. Thus the fraction of VO2max utilized and the RPE may increase during a long-distance run even when the steady-state VO2 is unchanged. V.-Ref.