Some research informed thoughts on adding brief sprints to low-intensity (LIT) sessions: 1. Keep the duration down to 3 to 4 seconds! This is the typical "Alactic" duration. Even extending to 6-8 seconds will result in significant lactate production. If you drop in a block of 15-30s sprints, then this is no longer a low-intensity session (particularly if you have a big "anaerobic capacity")! 2. There is probably a substantial "law of diminishing return" when doing these. What is a sufficient neuromuscular stimulus? Maybe 10-12 cycling sprints (there does seem to be some potentiation going on in the first few). Certainly not 60! 3. If you are strict on the sprint duration, the recovery time probably does not need to be more than 60-90 seconds. So, a sprint acceleration block would last 10-15min within a long easy ride. 4. Keep in mind that a single all-out sprint lasting 10-15 seconds will bump blood lactate up to 8-10 mmol/L and it will remain elevated (2-3mmol/L vs 1-1.5) for 30 minutes or more after. 5. Cycling and Running are different! The metabolic response is similar, but the mechanical load is much higher for running (Eccentric loading and those timing and foot placement sensitive eccentric-to-concentric transitions). So, build up to true full effort running accelerations SLOWLY if you have not been sprinting (trust me on this, I have the purple hamstring photos as proof)! Personally, I think short sprints are both fun and really beneficial for us age groupers because they counteract a downward spiral (we tend to lose muscle mass due to hormonal changes, so we sprint less, so we do not activate that muscle mass, so the atrophic spiral accelerates....). BUT, don't add sprints to every easy session, and be very careful on the duration of the sprints when you do them.