Author(s): SUMI, D., TAKII, Y., ABE, S., SAKAGUCHI, M., Institution: ASICS CORPORATION, Country: JAPAN, Abstract-ID: 987

INTRODUCTION:
Running speed frequently changes during a long-distance running event (e.g., 10000 m race in World Athletics Championships) [1]. Although it is anecdotally believed that fluctuation of running speed during long-distance event has a negative impact on running performance, its influence on physiological responses during running remains unclear. Therefore, the purpose of the present study was to determine the effect of fluctuating running speed during 10 km running on physiological variables compared to constant running speed.
METHODS:
Six male endurance runners completed two trials on different days, consisting of either fluctuating (FLU trial) or constant (CON trial) running speed during 10 km running on a treadmill. In the CON trial, running speed during 10 km running was constant at 80% of maximal oxygen uptake (VO2max), while running speed during 10 km running fluctuated between 75% and 85% of VO2max in the FLU trial. Running speed in the FLU trial fluctuated gradually (i.e., 75% - 80% - 85% of VO2max) every 600 m during 10 km running. Blood lactate levels and height of counter movement jump (CMJ) were evaluated before and after 10 km running. Moreover, respiratory gas variables [oxygen uptake (VO2) and expired minute ventilatory volume (VE)], heart rate (HR), rate of perceived exertion (RPE) using Borg’s CR10 scale, cadence and step length were measured during 10 km running.
RESULTS:
Actual running speeds were 14.0 ± 1.7 km/h, 15.1 ± 1.7 km/h, 16.1 ± 1.7 km/h for the 75%, 80% and 85% of VO2max, respectively. The time to completing 10 km running was same between two trials (40.4 ± 5.1 min). Blood lactate levels increased significantly in both trials (P = 0.042), whereas FLU trial showed greater blood lactate elevation (P = 0.015) after 10 km running (FLU: 4.3 ± 1.8 mmol/L, CON: 2.6 ± 1.8 mmol/L). Furthermore, the height of CMJ following 10 km running was significantly lower (P = 0.04) in the FLU trial (28.6 ± 4.3 cm) than in the CON trial (31.2 ± 3.1 cm). VO2, VE, HR and RPE during 10 km running fluctuated in the FLU trial, while these variables increased linearly in the CON trial. However, the mean values of VO2 (FLU: 48.2 ± 3.3 ml/kg/min, CON: 46.2 ± 3.5 ml/kg/min, P = 0.105), VE (FLU: 95 ± 13 L/min, CON: 86 ± 11 L/min, P = 0.09) and RPE (FLU: 5.3 ± 2.2, CON: 4.4 ± 1.5, P = 0.09) during 10 km running were tend to be higher in the FLU trial than in the CON trial. There was no significant different for mean values of HR (FLU: 164 ± 18 bpm, CON: 164 ± 19 bpm), cadence (FLU: 181.8 ± 11.9 steps/min, CON: 181.1 ± 11.9 steps/min) and step length (FLU: 1.36 ± 0.1 m, CON: 1.38 ± 0.2 m) during 10 km running between two trials.
CONCLUSION:
Fluctuating running speed partially exacerbated physiological response compared to constant running speed during 10 km running, even though the time to completing 10 km running was same.
[1]Quentin Mercier, Amandine Aftalion and Brian Hanley. Front Sports Act Living, 2:636428, 2021.