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Purpose and Methods: The present study was conducted to examine the pattern of plasma catecholamine and blood lactate responses to incremental arm and leg exercise. Seven untrained male subjects performed two incremental exercise tests on separate days in random order. One test consisted of 1-arm cranking (5W x 2 min(-1)), whereas the other exercise test was 2-leg cycling (20-25W x 2 min(-1)). Blood samples were obtained from the nonexercising arm during 1-arm cranking and from the same arm and vein during 2-leg cycling. Thresholds for blood lactate (T(La)), epinephrine (T(Epi)) and norepinephrine (T(NE)) were determined for each subject under both exercise conditions and defined as breakpoints when plotted as a function of power output., Results: When the two modes of exercise were compared, T(La), T(Epi), and T(NE) were all significantly lower for 1-arm cranking than for 2-leg cycling (P < 0.01). During 1-arm cranking, T(La) (0.96 +/- 0.10 L x min(-1)), T(Epi) (1.02 +/- 0.07 L x min(-1)), and T(NE) (1.07 +/- 0.09 L x min(-1)) occurred simultaneously. During 2-leg cycling, T(La) (1.77 +/- 0.20 L x min(-1)), T(Epi) (1.74 +/- 0.17 L x min(-1)), and T(NE) (1.98 +/- 0.17 L x min(-1)) occurred at similar levels of VO2 and were not significantly different. The correlation observed between the VO2 measured at the T(La) and T(Epi) was 0.917 for arm and 0.929 for leg exercise (P < 0.001). The epinephrine concentration ([Epi]) obtained at the T(La) was not significantly different for arm (0.144 ng x mL(-1)) and leg (0.152 ng x mL(-1)) exercise., Conclusions: The breakpoint in plasma [Epi] shifted in an identical manner and occurred simultaneously with that of T(La) regardless of the mode of exercise (arm or leg). The Epi concentrations observed at the T(La) agree with those previously reported to produce a rise in blood lactate during Epi infusion at rest. These results support the hypothesis that a rise in plasma [Epi] may contribute to the breakpoint in blood lactate that occurs during incremental exercise.

The individual anaerobic threshold (IAT) is defined as the highest metabolic rate where blood lactate (La) concentrations are maintained at a steady-state during prolonged exercise. The asymptote of the hyperbolic relationship between power output and time to fatigue has been defined as the critical power (CP), which, in theory, represents the highest metabolic rate where a steady-state response can be achieved during prolonged exercise. Since IAT and CP may define the same power output, the purpose of this study was to compare the gas exchange, blood La, and acid-base responses during exercise at the metabolic rates defined as IAT and CP. Fourteen males performed a maximal incremental cycle exercise test that was followed by a light active recovery period to determine IAT. Subsequently, subjects exercised to fatigue at five power outputs (calculated to elicit from 90% to 110% VO2max) to determine CP. IAT occurred at a significantly lower power output and VO2 (235 +/- 44 W and 2.97 +/- 0.47 l.min-1, respectively) compared with CP (265 +/- 39 W and 3.35 +/- 0.41 l.min-1, respectively). During 30 min of exercise at IAT, blood La levels increased during the initial 10 min to 3.9 +/- 1.9 mmol.l-1 but did not change during the final 15 min. Blood pH decreased to 7.32 +/- 0.04 at 5 min and did not change thereafter, while PCO2 fell from 41.5 +/- 3.2 mm Hg at 5 min to 36.2 +/- 3.6 mm Hg at 30 min. Only one subject completed 30 min of exercise at CP.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study has compared the metabolic and cardiorespiratory responses for two groups of male subjects during 20 min of exercise at the anaerobic threshold (AT), at AT + 1/3, and at AT + 2/3 of the difference (delta) between AT and VO2max. A log-log transformation of the lactate (LA)-power output relationship was used to define AT and divide subjects into a high (N = 7, AT = 51.9 +/- 1.5% VO2max) and low (N = 5; AT = 41.9 +/- 1.8% VO2max) AT group. No differences were observed between groups during exercise at AT for VE.VO2-(1), VE.VCO2(-1), pH, pCO2, blood LA, and plasma strong ions Na+, K+, and Cl-. Although blood LA values were significantly elevated for the low AT subjects (2.3 +/- 0.6 mmol.l-1) compared with the high AT group (1.0 +/- 0.1 mmol.l-1) during exercise at AT + 1/3 delta, no other differences between groups were noted. In contrast, marked differences were observed between groups during exercise at AT + 2/3 delta. The high AT group showed no change in VE (79.1 +/- 4.8 l.min-1), pH (7.367 +/- 0.01), pCO2 (37.3 +/- 1.2 mm Hg), and blood LA (2.9 +/- 0.3 mmol.l-1) during the final 10 min of the 20 min exercise test.(ABSTRACT TRUNCATED AT 250 WORDS)

The individual anaerobic threshold (IAT) is the highest metabolic rate at which blood lactate (LA) concentrations are maintained at a steady state during prolonged exercise. The purpose of this study was to compare the effects of active and passive recovery on the determination of the IAT before and after an endurance training program. Both before and after an 8-wk training program, nine subjects did two submaximal, incremental cycle exercise tests (30 W and 4 min per step) until LA was greater than or equal to 4 mmol.l-1. Blood was sampled repeatedly during exercise and for 12 min during the subsequent recovery period, which was passive for one test and active (approximately 35% VO2max) during the second test. An IAT metabolic rate and power output were calculated for the passive (IATp) and active (IATa) recovery protocols. On separate days, before and after training, five of the subjects exercised for 30 min at either the IATp or the IATa. Before training, IATa occurred at a higher (P less than 0.05) power output and absolute and relative VO2 compared to IATp. After training, VO2max and the power output and VO2 at IATa and IATp increased significantly; as a percent VO2max, IATp but not IATa increased. During the pretraining 30-min IAT rides, LA was higher during the IATa than the IATp test, but LA values did not change during the last 20 min of exercise. LA was similar for both 30-min IAT rides after training and did not change from 5 to 30 min of exercise. The LA steady-state concentrations ranged from 1.3 to 6.8 mmol.l-1.(ABSTRACT TRUNCATED AT 250 WORDS)