Abstract
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% Pmax below and above turn points. Peak load in IET was 5.3 ± 0.9 kg (Lamax: 2.20 ± 0.40 mmol·L−1; HRmax: 135 ± 15 b·min−1; VO2max: 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.
Highlights
The lactate shuttle theory [1,2,3] and the triphasic model of energy supply [4] have been extensively prescribed and were proven to be valid for cycle ergometer exercise [5], but has not been implemented yet in sports [6]
We hypothesize no significant difference between lactate and ventilation derived thresholds in small muscle group exercise and that these thresholds can be verified by lactate steady-state tests
lactate turn point 1 (LTP1) was determined at a load of 1.87 ± 0.57 kg and lactate turn point 2 (LTP2) at a load of 3.84 ± 0.71 kg
Summary
The lactate shuttle theory [1,2,3] and the triphasic model of energy supply [4] have been extensively prescribed and were proven to be valid for cycle ergometer exercise [5], but has not been implemented yet in sports [6]. The theory prescribes three phases, usually prescribed as aerobic, aerobic–anaerobic transition, and anaerobic phases, separated by to thresholds, the terms aerobic and anaerobic are misleading [7]. Several authors have proposed to use the terms first and second threshold or turn point [5,8] to avoid misunderstanding. For a better understanding of the interplay between local muscle and whole-body metabolism in small muscle incremental exercise, we, employed the lactate turn point concept [4,8,9,10] This concept [4,8,9,10] defines a metabolically balanced phase on local muscle level (phase I) below the first threshold, a systemically balanced metabolic phase (phase II) between thresholds 1 and 2 and a phase with no metabolically balanced situation (phase III) above threshold 2 [11].
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