Suchergebnisse

Accelerometer cut-points are commonly used to prescribe the amount of physical activity, but this approach includes no individual performance measures. As running kinetics change with intensity, acceleration measurements may provide more individual information. Therefore, the aim was to determine two intensity thresholds from accelerometer measures. A total of 33 participants performed a maximal incremental running test with spirometric and acceleration (Axivity AX3) measures at the left and right tibia. Ventilatory equivalents (VE/VO2, VE/VCO2) were used to determine a first and second ventilatory threshold (VT1/VT2). A first and second accelerometer threshold (ACT1/ACT2) were determined within the same regions of interest from vector magnitude (|v| = √(ax2 + ay2 + az2). Accelerometer data from the tibia presented a three-phase increase with increasing speed. Speed at VT1/VT2 (7.82 ± 0.39/10.91 ± 0.87 km/h) was slightly but significantly lower compared to the speed at ACT1/ACT2 from the left (7.71 ± 0.35/10.62 ± 0.72 km/h) and right leg (7.79 ± 0.33/10.74 ± 0.77 km/h). Correlation analysis revealed a strong relationship between speed at thresholds determined from spriometric data or accelerations (r = 0.98; p < 0.001). It is therefore possible to determine accelerometer thresholds from tibia placement during a maximal incremental running test comparable to standard ventilatory thresholds.

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.