Table 2.
Parameters (mean ± SEM, n = 9 for all parameters except eRTw and sTw TMS where n = 7) of the musculus vastus medialis (VM) function evaluated with electrical peripheral nerve (PNS) and transcranial magnetic (TMS) stimulation and before (PreEx) and after (PostEx) repeated knee extensor exercise to fatigue performed 1 h after ingestion of placebo or caffeine supplements.
| Parameters | Stimulus | Placebo |
Caffeine |
||
|---|---|---|---|---|---|
| PreEx | PostEx | PreEx | PostEx | ||
| I. Resting muscle | |||||
| potTw amplitude (% MVC)a | PNS | 24.7 ± 1.8 | 20.4 ± 2.1 | 24.4 ± 1.3 | 18.5 ± 1.5 |
| eRTw (%MVC)a | TMS | 21.2 ± 6.5 | 17.6 ± 4.6 | 22.5 ± 5.0 | 16.1 ± 3.8 |
| II. Knee extensors performing maximal voluntary isometric contraction (MVC) | |||||
| Force (N)a | 433.7 ± 25.6 | 376.0 ± 21.6 | 453.6 ± 12.5 | 402.0 ± 20.5 | |
| VM EMG MDF (Hz)a | 81.3 ± 6.8 | 92.4 ± 9.1 | 87.5 ± 8.0 | 94.2 ± 7.4 | |
| VM EMG RMS amplitude (mV)a | 0.22 ± 0.03 | 0.18 ± 0.01 | 0.21 ± 0.03 | 0.15 ± 0.02 | |
| VM EMG RMS amplitude (%Mmax)c | 4.04 ± 0.71 | 4.68 ± 1.09 | 4.84 ± 0.64 | 3.82 ± 0.72 | |
| sTw amplitude (% MVC)b | PNS | 3.7 ± 1.1 | 3.7 ± 0.9 | 2.5 ± 0.5 | 2.1 ± 0.5 |
| sTw amplitude (% MVC) | TMS | 2.3 ± 0.6 | 2.0 ± 0.7 | 1.2 ± 0.3 | 1.7 ± 0.4 |
| CT (ms)b | PNS | 29.3 ± 3.8 | 29.9 ± 3.4 | 23.6 ± 2.3 | 24.9 ± 2.9 |
| CT (ms) | TMS | 26.5 ± 3.2 | 21.4 ± 0.4 | 17.3 ± 2.3 | 18.3 ± 2.7 |
| HRT (ms) | PNS | 17.5 ± 0.8 | 17.4 ± 1.9 | 17.0 ± 1.1 | 15.3 ± 1.7 |
| RR (1 s−1)a,b | TMS | −11.4 ± 1.0 | −12.1 ± 1.3 | −12.5 ± 0.9 | −14.9 ± 0.9 |
| VM CSP (ms) | TMS | 201.5 ± 17.3 | 201.3 ± 15.4 | 210.3 ± 16.8 | 209.5 ± 22.1 |
potTw, potentiated twitch; sTw, twitch superimposed during MVC; eRTw, estimated resting twitch; MDF, median frequency of the EMG power spectral density; Mmax, maximal M-wave amplitude; CT, twitch contraction time; HRT, twitch half relaxation time; RR, twitch relaxation rate; CSP, cortical silent period.
aMain time effect.
bMain condition effect.
cInteraction effect.