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

The aim of our study is to determine the first (LTP₁) and the second (LTP₂) lactate turn points during an incremental bicep curl test and to verify these turn points by ventilatory turn points (VT₁ and VT₂) 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, VT₁ and VT₂ 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). LTP₁ was detected at 1.9 ± 0.6 kg (La: 0.86 ± 0.36 mmol·L^-1; HR 90 ± 13 b·min^-1; VO₂: 0.50 ± 0.05 L·min^-1) and LTP₂ at 3.8 ± 0.7 kg (La: 1.38 ± 0.37 mmol·L^-1; 106 ± 10 b·min^-1; VO₂: 0.62 ± 0.11 L·min^-1). Constant-load tests showed a lactate steady-state in all tests except above LTP₂, with early termination after 16.5 ± 9.1 min. LTP₁ and LTP₂ could be determined in IET, which were not significantly different from VT₁/VT₂. Constant-load exercise validated the three-phase concept, and a steady-state was found at resting values below VT₁ and in all other tests except above LTP₂. It is suggested that the three-phase model is also applicable to small muscle group exercise.