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Erschienen in:
18.04.2022 | Original Article
A longitudinal study on the interchangeable use of whole-body and local exercise thresholds in cycling
Erschienen in: European Journal of Applied Physiology | Ausgabe 7/2022
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Purpose
This study longitudinally examined the interchangeable use of critical power (CP), the maximal lactate steady state (MLSS) and the respiratory compensation point (RCP) (i.e., whole-body thresholds), and breakpoints in muscle deoxygenation (m[HHb]BP) and muscle activity (iEMGBP) (i.e., local thresholds).
Methods
Twenty-one participants were tested on two timepoints (T1 and T2) with a 4-week period (study 1: 10 women, age = 27 ± 3 years, \(\dot{V}{\text{O}}_{{2{\text{peak}}}}\) = 43.2 ± 7.3 mL min−1kg−1) or a 12-week period (study 2: 11 men, age = 25 ± 4 years, \(\dot{V}{\text{O}}_{{2{\text{peak}}}}\) = 47.7 ± 5.9 mL min−1 kg−1) in between. The test battery included one ramp incremental test (to determine RCP, m[HHb]BP and iEMGBP) and a series of (sub)maximal constant load tests (to determine CP and MLSS). All thresholds were expressed as oxygen uptake (\(\dot{V}{\text{O}}_{2}\)) and equivalent power output (PO) for comparison.
Results
None of the thresholds were significantly different in study 1 (\(\dot{V}{\text{O}}_{2}\): P = 0.143, PO: P = 0.281), but differences between whole-body and local thresholds were observed in study 2 (\(\dot{V}{\text{O}}_{2}\): P < 0.001, PO: P = 0.024). Whole-body thresholds showed better 4-week test–retest reliability (TEM = 88–125 mL min−1 or 6–10 W, ICC = 0.94–0.98) compared to local thresholds (TEM = 189–195 mL min−1 or 15–18 W, ICC = 0.58–0.89). All five thresholds were strongly associated at T1 and T2 (r = 0.75–0.99), but their changes from T1 to T2 were mostly uncorrelated (r = − 0.41–0.83).
Conclusion
Whole-body thresholds (CP/MLSS/RCP) showed a close and consistent coherence taking into account a 3–6%-bandwidth of typical variation. In contrast, local thresholds (m[HHb]BP/iEMGBP) were characterized by higher variability and did not consistently coincide with the whole-body thresholds. In addition, we found that most thresholds evolved independently of each other over time. Together, these results do not justify the interchangeable use of whole-body and local exercise thresholds in practice.