Uphill versus downhill high-intensity training effectiveness in preserving vascular function and exercise performance in runners who reduce their regular endurance training

PURPOSE: The COVID-19 restrictions have limited outdoor physical activities. High-intensity training (HIT) may be a valid indoor alternative. We tested whether an indoor HIT is effective in maintaining vascular function and exercise performance in runners who reduce their usual endurance training, and whether a downhill HIT is as effective as an uphill one for such purposes. METHODS: Sixteen runners performed the same 6-week HIT either uphill (UP, eight runners) or downhill (DOWN, eight runners). Eight runners continuing their usual endurance training acted as a control group (CON). The following data were collected before vs after our HIT: vascular conductance during rapid leg vasodilation to assess vasodilation capacity; V̇O(2max) through running incremental test to exhaustion; 2000 m running time; neuromuscular indexes related to lower-limb muscle strength. RESULTS: Both uphill and downhill HIT failed in maintaining the pre-HIT leg vasodilation capacity compared to CON, which was, however, blunted more after uphill than downhill HIT. V̇O(2max) and 2000 m time were similar after downhill HIT compared to CON, and augmented after uphill HIT compared to CON and DOWN. Indexes of lower-limb muscle strength were similar before vs after HIT and among groups. CONCLUSION: Our HIT was ineffective in maintaining the pre-HIT leg vasodilation capacity compared to runners continuing their usual low-intensity endurance training, but did not lead to reductions in V̇O(2max), 2000 m time performance, and indexes related to lower-limb muscle strength. Our data show an appealing potential for preserving exercise performance with low cardiorespiratory effort via downhill running.