Studies like the one below are the reason that many years ago I set the protocol for rest periods during interval workouts in TheETG training program at full recoveries. No running or jogging in between reps. The only activity allowed is to walk, stand, sit, or lay down. An abbreviated warmup can be done prior to the next rep if necessary.
The training stimulus is in training at certain velocities not in playing physiologically nonsensical games that coaches often play with the length of the rest periods in between reps. And the lower cortisol [stress hormone] level is a more logical route to take.
“This study compared run-based repeated-sprint performance across various sprint phases and underlying physiological responses between active and passive recoveries.”
“Nine students completed 2 bouts (active and passive recoveries) of 10 × 20 m sprints interspersed with 30 seconds recoveries in a randomized crossover fashion.”
“Sprint times and decrements were calculated for each split (0–5, 5–15, 15–20, and 0–20 m) across each sprint. Blood lactate concentration, heart rate, and rating of perceived exertion were measured at various time-points.”
“Passive recovery promoted improved performance times and decrements across all splits, and lower post-test Blood lactate, HR (bout 3 onwards), and RPE (bout 4 onwards) when compared with active recovery.”
“The present data indicate that passive recovery promoted superior performance across run-based run-based repeated-sprint performance, with earlier performance deterioration and greater physiological load evident during active recovery.”
A.T. Scanlan, M.C. Madueno
Passive recovery promotes superior performance and reduced physiological stress across different phases of short-distance repeated sprints
Journal of Strength & Conditioning Research:— Volume 30 #9 — September 2016 — page 2540