Intensity Thresholds and Maximal Lactate Steady State in Small Muscle Group Exercise

The aim of our study is to determine the first (LTP(1)) and the second (LTP(2)) lactate turn points during an incremental bicep curl test and to verify these turn points by ventilatory turn points (VT(1) and VT(2)) and constant-load exercise tests. Twelve subjects performed a one-arm incremental bicep curl exercise (IET) after a one repetition maximum (1RM) test to calculate the step rate for the incremental exercise (1RM/45). Workload was increased every min at a rate of 30 reps/min until maximum. To verify LTPs, VT(1) and VT(2) were determined from spirometric data, and 30 min constant-load tests (CL) were performed at 5% P(max) below and above turn points. Peak load in IET was 5.3 ± 0.9 kg (La(max): 2.20 ± 0.40 mmol·L(−1); HR(max): 135 ± 15 b·min(−1); VO(2max): 1.15 ± 0.30 L·min(−1)). LTP(1) was detected at 1.9 ± 0.6 kg (La: 0.86 ± 0.36 mmol·L(−1); HR 90 ± 13 b·min(−1); VO(2): 0.50 ± 0.05 L·min(−1)) and LTP(2) at 3.8 ± 0.7 kg (La: 1.38 ± 0.37 mmol·L(−1); 106 ± 10 b·min(−1); VO(2): 0.62 ± 0.11 L·min(−1)). Constant-load tests showed a lactate steady-state in all tests except above LTP(2), with early termination after 16.5 ± 9.1 min. LTP(1) and LTP(2) could be determined in IET, which were not significantly different from VT(1)/VT(2). Constant-load exercise validated the three-phase concept, and a steady-state was found at resting values below VT(1) and in all other tests except above LTP(2). It is suggested that the three-phase model is also applicable to small muscle group exercise.