Table 1.
Neuromuscular function of the wrist flexors depending on the wrist joint angle.
Wrist joint angle | P-values | |||||
---|---|---|---|---|---|---|
Extension (– 30°) | Neutral (0°) | Flexion (30°) | −30° vs. 0° | −30° vs. 30° | 30° vs. 0° | |
Maximal voluntary torque (N·m) | 16.08 ± 2.78 | 19.17 ± 3.12 | 18.46 ± 2.46 | <0.001** | 0.001** | 0.552 |
Voluntary activation (%) | 98.11 ± 2.65 | 97.40 ± 3.52 | 96.06 ± 4.05 | 0.742 | 0.005** | 0.055 |
Central activation ratio (%) | 99.21 ± 1.05 | 99.20 ± 1.01 | 98.89 ± 1.06 | n.a. | n.a. | n.a. |
Interpolated twitch torque (N·m) | 0.118 ± 0.154 | 0.149 ± 0.186 | 0.200 ± 0.191 | 1 | 0.039* | 0.186 |
Control twitch torque (N·m) | 6.02 ± 0.93 | 5.68 ± 0.85 | 5.17 ± 0.87 | 0.192 | 0.002** | 0.017* |
RMS·M−1 | ||||||
Flexor carpi radialis (FCR) | 0.088 ± 0.023 | 0.087 ± 0.030 | 0.084 ± 0.030 | n.a. | n.a. | n.a. |
Extensor carpi radialis brevis (ECRB) | 0.042 ± 0.018 | 0.041 ± 0.016 | 0.046 ± 0.015 | n.a. | n.a. | n.a. |
ECRB·FCR−1 ratio | 0.50 ± 0.24 | 0.52 ± 0.23 | 0.62 ± 0.30 | 1 | 0.021* | 0.174 |
Mmax (mV) | ||||||
FCR | 9.00 ± 3.03 | 9.29 ± 2.95 | 10.63 ± 3.77 | 1 | 0.009** | 0.033* |
ECRB | 6.98 ± 2.53 | 6.90 ± 2.05 | 6.47 ± 2.03 | n.a. | n.a. | n.a. |
Peak twitch torque (N·m) | ||||||
SS | 1.58 ± 0.34 | 1.25 ± 0.28 | 0.98 ± 0.24 | <0.001** | <0.001** | <0.001** |
PS100 | 4.01 ± 0.65 | 3.44 ± 0.66 | 2.90 ± 0.51 | <0.001** | <0.001** | <0.001** |
SSPOT | 2.99 ± 0.38 | 2.69 ± 0.44 | 2.29 ± 0.36 | 0.006** | <0.001** | <0.001** |
PS100POT | 6.29 ± 0.99 | 5.93 ± 0.92 | 5.40 ± 0.95 | 0.31 | <0.001** | 0.06 |
Rate of twitch torque development (N·m·s–1) | ||||||
SS | 23.16 ± 4.27 | 18.55 ± 3.46 | 15.63 ± 4.00 | <0.001** | <0.001** | 0.032* |
PS100 | 52.32 ± 9.22 | 47.10 ± 8.76 | 40.40 ± 7.12 | 0.009** | <0.001** | 0.001** |
SSPOT | 53.42 ± 8.91 | 50.30 ± 7.84 | 45.01 ± 7.11 | 0.46 | 0.001** | 0.067 |
PS100POT | 86.32 ± 14.74 | 85.98 ± 12.68 | 83.27 ± 15.70 | n.a. | n.a. | n.a. |
Rate of twitch torque relaxation (N·m·s–1) | ||||||
SS | 12.77 ± 3.05 | 11.09 ± 2.94 | 9.65 ± 2.87 | 0.009** | 0.001** | 0.016* |
PS100 | 31.60 ± 5.44 | 30.68 ± 5.35 | 29.30 ± 5.93 | n.a. | n.a. | n.a. |
SSPOT | 30.01 ± 4.15 | 30.37 ± 4.05 | 27.91 ± 4.64 | n.a. | n.a. | n.a. |
PS100POT | 52.15 ± 9.71 | 56.36 ± 6.86 | 57.76 ± 7.94 | 0.114 | 0.038* | 1 |
Electromechanical delay (ms) | ||||||
SS | 9.04 ± 0.82 | 9.80 ± 1.03 | 11.61 ± 2.65 | 0.009** | 0.004** | 0.017* |
PS100 | 9.11 ± 0.78 | 9.87 ± 1.07 | 11.70 ± 2.55 | 0.004** | 0.002** | 0.008** |
SSPOT | 8.56 ± 0.96 | 8.94 ± 0.85 | 10.72 ± 1.63 | 0.556 | <0.001** | <0.001** |
PS100POT | 8.22 ± 1.18 | 9.22 ± 1.03 | 10.67 ± 1.70 | 0.073 | <0.001** | 0.001** |
Twitch contraction time (ms) | ||||||
SS | 68.24 ± 5.27 | 67.31 ± 5.29 | 63.41 ± 8.49 | 1 | 0.029* | 0.211 |
PS100 | 77.09 ± 5.85 | 73.02 ± 3.98 | 71.94 ± 5.61 | <0.001** | 0.002** | 0.757 |
SSPOT | 56.56 ± 6.18 | 53.61 ± 4.98 | 51.78 ± 8.97 | 0.173 | 0.074 | 0.701 |
PS100POT | 73.06 ± 4.01 | 69.06 ± 5.15 | 65.44 ± 6.52 | 0.003** | <0.001** | 0.036* |
Twitch half-relaxation time (ms) | ||||||
SS | 63.17 ± 9.92 | 57.63 ± 7.67 | 51.97 ± 6.94 | 0.019* | 0.002** | 0.010** |
PS100 | 63.96 ± 7.64 | 56.09 ± 5.52 | 50.09 ± 7.08 | 0.001** | <0.001** | 0.001** |
SSPOT | 50.33 ± 7.10 | 44.78 ± 8.50 | 41.67 ± 6.19 | <0.001** | <0.001** | 0.406 |
PS100POT | 61.00 ± 7.13 | 52.72 ± 6.23 | 46.72 ± 5.01 | <0.001** | <0.001** | <0.001** |
Percentage changes peak twitch torque | ||||||
SS vs. SSPOT | 92.84 ± 27.71 | 119.59 ± 34.52 | 142.88 ± 49.17 | <0.001** | <0.001** | 0.111 |
PS100 vs. PS100POT | 57.82 ± 15.44 | 75.75 ± 26.12 | 88.74 ± 28.77 | 0.010** | 0.002** | 0.189 |
SS vs. PS100 | 158.89 ± 47.04 | 180.52 ± 54.37 | 205.49 ± 60.15 | 0.013* | <0.001** | 0.002** |
SSPOT vs. PS100POT | 111.23 ± 26.52 | 122.66 ± 28.02 | 136.56 ± 31.61 | 0.074 | <0.001** | 0.063 |
Please note that post-hoc comparisons are only available if the ANOVA with repeated measures indicated a statically significant difference (P-values in bold are significant,
P ≤ 0.050,
P ≤ 0.010). n. a., not applicable because the ANOVA did not indicate a main effect of angle; RMS·M−1, root mean square of the EMG signal normalized to the maximal M-wave (Mmax); SS, unpotentiated peak twitch torque evoked by a single stimulus; PS100, unpotentiated peak twitch torque evoked by paired stimuli at 100 Hz [inter-stimulus interval (ISI) 10 ms]; SSPOT, potentiated peak twitch torque evoked by a single stimulus; PS100POT, potentiated peak twitch torque evoked by paired stimuli at 100 Hz (ISI 10 ms). Values are expressed as means ± standard deviations.