Author(s): CASADO, A., SOLANO-LIZCANO, V., RANIERI, L.E., RODRÍGUEZ-CASTAÑO, A., TRUJILLO-COLMENA, D., GARCÍA-ORTIZ, C., DEL COSO, J., Institution: UNIVERSIDAD REY JUAN CARLOS, Country: SPAIN, Abstract-ID: 2294

INTRODUCTION:
Training to improve performance in distance runners is characterized by a combination of high volume of moderate intensity continuous runs (MICR) and low volume of high intensity interval training (HIIT) [1]. HIIT is typically conducted between the speed associated with the second ventilatory threshold (sVT2) and maximum aerobic speed (MAS) [1]. However, sprint interval training (SIT), which consists of repeated maximal efforts separated by relatively long recoveries, can induce robust adaptations and performance improvement [2]. These adaptations have been linked to potent metabolic stress and molecular signaling associated with mitochondrial biogenesis and metabolic regulation [3]. Nonetheless, its value as a low load complement within predominantly MICR-based routines remains unknown. Furthermore, the effects on performance between short and long-SIT protocols have not been investigated yet in distance runners. Therefore, the aim of the present study was twofold: (1) to determine the effects on performance and its physiological determinants of adding low training load SIT protocols to the training of recreational distance runners, and (2) to compare the effects generated between short- and long-SIT sessions.
METHODS:
Twenty-nine trained runners (11 women, 18 men; baseline maximum oxygen uptake [VO2max]: 53.1±6.5 mL·kg⁻¹·min⁻¹) completed a randomized controlled parallel-group study. Physiological performance determinants were assessed via breath-by-breath gas analysis during incremental and constant pace treadmill tests, while performance was evaluated through 3000-m and 100-m track tests. For the intervention, participants followed a standardized endurance program lasting 8 weeks and were divided into 2 experimental groups who also performed 2 SIT sessions per week (short- [3–5 x 50–80 m], and long-SIT [2–4 x 100–200 m] groups), and a control group. Heart rate was monitored during the training period and internal load was quantified. A 2×3 repeated-measures analysis of variance was used to analyze main time and between-group effects.
RESULTS:
Training load was similar between groups (p>0.05). No significant Group x Time interactions were observed for MAS, VO2max, running economy, or sVT2 (p>0.05). sVT1 improved significantly over time (p<0.001). Additionally, a main time effect of 3000-m performance was found (p=0.002 ηp² = 0.310), and post-hoc analysis revealed that significant gains were exclusive to the long SIT group (p=0.044, d=0.69). Sprint performance (100 m, 50 m, 25 m) improved significantly in both SIT groups (p<0.05), without differences in the control group.
CONCLUSION:
Supplementing habitual training with low-load SIT during 8 weeks effectively enhances sprint capacity without altering central determinants of aerobic performance in recreational distance runners. While both formats improve maximum speed, longer sprints (>100 m) appear to elicit a greater 3000-m performance in distance runners.

1 Casado et al. (2022)
2 Gibala et al. (2006)
3 Gibala et al. (2009)