Researchers at the University of Jyväskylä compared two-week blocks of low-intensity endurance training versus high-intensity interval training (HIIT) on performance and recovery in recreational runners. Both strategies enhanced endurance after just two weeks by substantially increasing training load beyond participants' usual routines.
Distance runners typically blend low-intensity sessions with moderate-to-high intensity efforts weekly. However, block periodization—focusing intensely on one training type for a short period—may offer unique advantages.
This study tested block periodization by having participants either boost low-intensity volume by 70% or complete 10 sessions of 6 x 3-minute intervals (5 sessions per week) over two weeks. For recreational exercisers, short blocks of either low- or high-intensity training proved effective.
“Both groups improved their 3000m running performance immediately after the block,” says doctoral researcher Olli-Pekka Nuuttila from the University of Jyväskylä. “The interval group shaved off an average of 13 seconds, while the low-intensity group improved by 11 seconds. After a recovery week, the interval group averaged 19 seconds faster than baseline, and the low-intensity group 17 seconds quicker. No statistically significant differences emerged between groups.”
Recovery markers revealed key differences: lower limb muscle soreness rose significantly only in the interval group, persisting through training and recovery weeks compared to the low-intensity group. Greater soreness correlated with smaller gains in a walking test. Resting norepinephrine levels spiked post-block in the interval group and stayed elevated after recovery. Nighttime heart rate variability also dropped more in the interval group during week one.
“Our recovery data indicate HIIT blocks are more demanding than high-volume low-intensity ones,” Nuuttila summarizes. “Prioritize recovery post-block and monitor it via subjective measures to prevent overtraining.”
Prior research on block periodization in recreational athletes has been limited, especially regarding multi-faceted recovery and performance shifts across varied training emphases.
Endurance gains were assessed via 3000m time trials, with recovery tracked through nighttime heart rate variability, perceived recovery scales, and urinary/blood hormone analyses.
Participants were recreationally active men and women aged 20-45 (15 per group).
