# Changes in balance ability, power output, and stretch-shortening cycle utilisation after two high-intensity intermittent training protocols in endurance runners PMID: 30356558 Journal: Journal of Sport and Health Science Published: 2016 Authors: García-Pinillos F, Párraga-Montilla JA, Soto-Hermoso VM, Latorre-Román PA ## Question How do two equal-volume running HIIT structures acutely affect postural control, vertical jump power, and stretch-shortening-cycle utilization in endurance runners? ## Summary Eighteen recreational endurance runners completed two acute track HIIT workouts with the same 4 km volume: 10 x 400 m with 90 s passive recovery and 40 x 100 m with 30 s passive recovery. The shorter-repeat protocol let runners move faster with lower RPE and no significant changes in jumping, balance, or stretch-shortening-cycle measures, while the 400 m repeat protocol improved CMJ and SJ but worsened postural control. ## Population - 18 recreationally trained endurance runners in cross-country season. - Sample size: 18 - Age: 30.89 +/- 11.69 years - Sex: 16 males, 2 females - Fitness level: Recreationally trained endurance runners, minimum 4 years regular training - Health status: No limiting injury in prior 3 months; annual medical exams reported ## Methodology - Acute repeated-measures field comparison of two HIIT running protocols - Two testing sessions separated by 7 days - Outdoor 400 m synthetic track during cross-country competition season - Controlled study design. ## Protocol - 10 x 400 m running HIIT. - Modality: Outdoor running. - Work intervals: 400 m. - Recovery: 90 s passive standing recovery. - Sets or repetitions: 10 repetitions. - Intensity: Above vVO2max; 107.17 +/- 2.83% vVO2max on average. - Session duration: 4 km high-intensity running plus recovery after 20 min warm-up. - Frequency: One acute session. - Program length: Acute field comparison. - Progression: None. - 40 x 100 m running HIIT. - Modality: Outdoor running. - Work intervals: 100 m. - Recovery: 30 s passive standing recovery. - Sets or repetitions: 40 repetitions. - Intensity: Above vVO2max; 125.40 +/- 4.89% vVO2max on average. - Session duration: 4 km high-intensity running plus recovery after 20 min warm-up. - Frequency: One acute session. - Program length: Acute field comparison. - Progression: None. ## Outcomes ### Jump height Status: mixed CMJ and SJ improved after 10 x 400 m but did not significantly change after 40 x 100 m. 10 x 400 m CMJ and SJ p<0.05; discussion reports CMJ +5.18% and SJ +6.43%. ### Balance Status: worse/safety concern Postural control worsened after 10 x 400 m but not after 40 x 100 m. 10 x 400 m CoP area p=0.006, length p=0.001, velocity p=0.004; 40 x 100 m p=0.812, p=0.220, p=0.364. ### SSC Status: no clear change Stretch-shortening-cycle utilization did not significantly change in either protocol. PSA and RSI p values were non-significant in both protocols. ### Intensity Status: mixed 40 x 100 m had faster pace and higher mean HR, while lactate and HRpeak were similar. Pace and %vVO2max p<0.001; HRmean p<0.001; BLa p=0.670; HRpeak p=0.067. ## Practical Insights - For trained runners, splitting the same 4 km HIIT volume into shorter 100 m repeats may preserve postural control better than 400 m repeats. - Acute balance measures may be worth monitoring after longer high-intensity running repeats. ## Limitations - Small sample - Non-randomized protocol order - Acute field study only - Intensity was not precisely prescribed beyond above-vVO2max self-paced running ## Safety And Adherence - No adverse events were reported. - Participants had no injury in the prior 3 months and were asked to avoid heavy exercise for 72 h before testing. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/30356558/) (pubmed) - [DOI](https://doi.org/10.1016/j.jshs.2015.09.003) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6188880/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.