Table 2.
Effects of 5 km time trial performances (TT, self-selected effort) on fatigue variables
| TT–hypoxia (CaO2 17.6 ml dl−1; 483 s; 275 W) | TT–normoxia (CaO2 20.9 ml dl−1; 458 s; 314 W) | TT–iso-oxia (CaO2 22.6 ml dl−1; 451 s; 331 W) | TT–hyperoxia (CaO2 24.4 ml dl−1; 438 s; 357 W) | P | |
|---|---|---|---|---|---|
| Twitch variables | |||||
| 1 Hz potentiated (N) | −34.3 ± 4.7 | −35.1 ± 4.2 | −33.4 ± 2.1 | −35.4 ± 1.3 | 0.19 |
| 1 Hz (N) | −27.1 ± 2.6 | −28.6 ± 3.8 | −28.5 ± 2.2 | −29.8 ± 2.5 | 0.78 |
| 10 Hz (N) | −29.6 ± 4.6 | −32.5 ± 4.2 | −31.1 ± 2.4 | −32.8 ± 3.0 | 0.64 |
| 50 Hz (N) | −26.5 ± 4.6 | −26.2 ± 4.0 | −25.3 ± 1.9 | −27.9 ± 1.5 | 0.52 |
| 100 Hz (N) | −27.3 ± 4.6 | −25.4 ± 3.5 | −24.7 ± 1.7 | −27.8 ± 2.3 | 0.43 |
| Mean of 4 frequenciesa (N) | −27.6 ± 4.1 | −27.9 ± 3.6 | −27.0 ± 1.5 | −29.4 ± 1.8 | 0.39 |
| Within-twitch variables | |||||
| MRFDb (N s−1) | −25.8 ± 3.9 | −25.6 ± 3.2 | −25.9 ± 2.1 | −28.3 ± 2.3 | 0.70 |
| MRRb (N s−1) | −29.1 ± 5.1 | −26.6 ± 3.7 | −29.1 ± 3.5 | −30.3 ± 2.6 | 0.67 |
| CTb (s) | −3.3 ± 0.7 | −4.5 ± 1.2 | −4.2 ± 0.8 | −4.0 ± 0.8 | 0.52 |
| RT0.5b (s) | 8.3 ± 1.9 | 8.1 ± 2.7 | 8.0 ± 1.4 | 7.9 ± 1.2 | 0.98 |
| MVC (N) | −12.5 ± 4.3 | −13.9 ± 1.6 | −12.5 ± 1.8 | −10.8 ± 2.0 | 0.64 |
Values are expressed as percentage change from pre-exercise baseline measurement to 2.5 min post-exercise. All variables changed significantly, P < 0.05 (n= 8).
a
1–100 Hz
b
based on 1 Hz non-potentiated (single twitch); MRFD, maximal rate of force development; MRR, maximal rate of relaxation; CT, contraction time; RT0.5, half-relaxation time; MVC, maximal voluntary contraction. Pre-exercise, resting mean values for twitch forces (1–100 Hz) are represented in Fig. 4. Pre-exercise, resting mean values for MRFD, MRR, CT, RT0.5 and MVC were 1063 ± 16 N s−1, −784 ± 11 N s−1, 0.27 ± 0.02 s, 0.12 ± 0.01 s, and 537 ± 5 N, respectively.