Summary
Part 2 of the interval training Q&A with researcher Michael Rosenblat, covering practical application of HIIT and SIT for endurance athletes. They discuss how aging athletes should start with shorter, lower-intensity intervals before progressing to longer or harder efforts, and how to distribute interval training across swimming, cycling, and running in triathlon. Rosenblat shares findings from his meta-regression of 77 groups and 550 participants showing that active versus passive recovery between intervals doesn't significantly affect time trial performance outcomes. They discuss over-under intervals (cruising around threshold), central versus peripheral adaptations from high-intensity training, and how SIT produces strong neuromuscular responses. The recommended approach is 2 interval sessions per week (favoring bike over run for injury prevention), with SIT for running to improve leg speed and HIIT on the bike.
Key Points
- Aging athletes should start with shorter 1-minute intervals at lower intensity before progressing to longer bouts
- Meta-regression of 77 groups (550 people): active vs passive recovery between intervals doesn't significantly affect performance outcomes
- Recommended: 2 interval sessions per week, split between cycling and running
- Favor bike over run for hard interval sessions due to lower injury risk from eccentric loading
- SIT for running improves neuromuscular response and leg speed; HIIT on bike may be more effective for aerobic gains
- Over-under intervals (105% FTP alternating with 80-85% FTP) practice lactate clearance
- SIT adaptations between 5-second and 30-second bouts are similar, suggesting neuromuscular rather than metabolic drivers
- Both central (cardiac) and peripheral (mitochondrial) adaptations occur with interval training; the whole system needs to improve together
Key Moments
How aging athletes should start interval training
Start with shorter 1-minute intervals at lower intensity to get the body used to the physical stress, even though longer 4-6 minute intervals are more beneficial for endurance. This reduces injury risk, especially for running.
"I would certainly recommend somebody who's just starting out start with one minute intervals."
Active vs passive recovery between sprints
Meta-regression of 77 groups (550 people) shows active vs passive recovery between intervals doesn't significantly affect time trial performance, regardless of whether you're doing HIT or SIT.
"the results from the meta regression show that it probably doesn't matter regardless of, of the type of interval training, whether you're doing active or passive training,"
SIT neuromuscular benefits for running speed
SIT on the run improves leg speed through neuromuscular adaptations. Similar improvements between 5-second and 30-second SIT bouts suggest the benefit is more neuromuscular than metabolic.
"sprint interval training on the run can be very useful for some athletes that just seem to have a bit of a slower leg speed and aren't really good at getting up to speed and running fast."
