Table 1.
Cardiorespiratory and biomechanical parameters by pooling all running speeds.
| Treadmill slope (%) | −20 | −10 | −5 | 0 | +5 | +10 | +15 | +20 |
|---|---|---|---|---|---|---|---|---|
| N | 21 | 29 | 26 | 29 | 26 | 29 | 16 | 6 |
| Corrected (ml·min−1·kg−1) | 26.5 ± 4.4# | 28.8 ± 3.5# | 32.5 ± 3.0* | 39.9 ± 3.5* | 47.1 ± 4.4* | 53.6 ± 4.0#$ | 58.2 ± 9.3#$ | 67.5 ± 4.2# |
| Respiratory exchange ratio (%) | 0.77 ± 0.05# | 0.78 ± 0.03# | 0.81 ± 0.04* | 0.86 ± 0.05* | 0.90 ± 0.06* | 0.94 ± 0.03#$ | 0.95 ± 0.06#$ | 1.00 ± 0.03#$ |
| VE (l·min−1) | 56.0 ± 9.3# | 54.8 ± 9.4# | 60.2 ± 10.1# | 73.1 ± 13.3* | 86.5 ± 16.7* | 100.1 ± 17.9#$ | 107.4 ± 20.7#$ | 120.4 ± 18.9#$ |
| RF (breaths·min−1) | 46 ± 10# | 39 ± 7#$ | 37 ± 7$ | 36 ± 8$ | 39 ± 8$ | 41 ± 9#$ | 39 ± 7$ | 40 ± 7 |
| HR (bpm) | 133 ± 17# | 129 ± 20# | 132 ± 16# | 144 ± 19$ | 156 ± 14#$ | 167 ± 15#$ | 169 ± 12#$ | 174 ± 10#$ |
| b[La] (mmol·l−1) | − | − | 3.0 ± 1.5 | 3.5 ± 1.2 | 4.3 ± 2.4 | 5.2 ± 1.6# | 5.6 ± 3.0# | 7.5 ± 1.9# |
| RPE | 10 ± 2 | 9 ± 1 | 9 ± 2# | 11 ± 2* | 12 ± 2$ | 14 ± 1$ | 15 ± 2$ | 16 ± 2$ |
| Step length (cm) | 116 ± 10 | 112 ± 7 | 113 ± 6 | 112 ± 6 | 104 ± 11$ | 93 ± 8#$ | 86 ± 9#$ | 82 ± 3#$ |
| Step frequency (Hz) | 2.76 ± 0.10 | 2.70 ± 0.11#$ | 2.72 ± 0.12 | 2.76 ± 0.11 | 2.76 ± 0.14 | 2.79 ± 0.13 | 2.79 ± 0.13 | 2.71 ± 0.09 |
| Contact time (ms) | 255 ± 29# | 273 ± 25 | 275 ± 24$ | 274 ± 25$ | 285 ± 27$ | 298 ± 29#$ | 301 ± 25#$ | 322 ± 12#$ |
| Aerial time (ms) | 107 ± 32# | 98 ± 21# | 95 ± 18 | 89 ± 20$ | 78 ± 17$ | 62 ± 20#$ | 58 ± 22#$ | 48 ± 12#$ |
| Fz (N) | 1,467 ± 225 | 1,438 ± 232 | 1,430 ± 243 | 1,409 ± 252 | 1,347 ± 240$ | 1,259 ± 193#$ | 1,206 ± 193#$ | 1,194 ± 106#$ |
| Δy (cm) | 6.3 ± 0.6 | 6.6 ± 0.5#$ | 6.5 ± 0.5# | 6.2 ± 0.5 | 6.1 ± 0.6 | 5.8 ± 0.5#$ | 5.7 ± 0.7#$ | 5.9 ± 0.6 |
Values are means ± SD, corrected oxygen uptake (corrected ) from baseline oxygen uptake () 5.0 ± 0.6 ml·min−1·kg−1, minute pulmonary ventilation (VE), respiratory frequency (RF), heart rate (HR), blood lactate concentration (b[La]), rate of perceived exertion (RPE), maximal vertical ground reaction force (Fz), vertical displacement of the center of mass during ground contact (Δy). Asterisks (
*
) indicate a statistically significant difference vs. all other conditions,
#
vs. 0% slope, and
$
vs. −20% slope (p < 0.05).