--- title: "What makes an interval session count?" date: 2026-11-01 categories: ["Training","Data & monitoring"] url: https://www.semiprocycling.com/digest/what-makes-an-interval-session-count author: Damian Ruse (SEMIPRO Cycling) --- # What makes an interval session count? ![](https://buzz.semiprocycling.com/newsletter-images/65e07345-0cf4-473a-a054-c94a5c87c858/96a37500ac2bf535a34d9f8cc89dd52df40d6ab92561cee96dc91054ce0e7994.jpg) High-intensity intervals are widely used to improve aerobic fitness, but there is still debate about which session designs provide the most useful stimulus. One common measure is the time spent close to maximal oxygen uptake, or VO₂max: how long the body sustains a very high rate of oxygen use during the session. The rationale is that sustained demand on oxygen delivery and use may support aerobic adaptation. The unresolved question is how reliably more time near VO₂max translates into better fitness after several weeks of training. A systematic review by Patrick Schoenmakers and colleagues examined 86 studies covering 239 interval protocols. The studies included cycling, running and other sports, across different ages and training backgrounds. The main analysis compared oxygen uptake during individual sessions, rather than improvements after a complete training programme. **Longer intervals produced more time near VO₂max.** Work periods of at least two minutes accumulated more time above 90% and 95% of VO₂max than short intervals of 30 seconds or less, or moderate-duration intervals between 30 seconds and two minutes. The difference remained after adjusting for total session duration. However, the longer-interval sessions also contained more actual work, so these were not uniformly workload-matched comparisons. Oxygen uptake takes time to rise at the start of an effort. Longer intervals allow more time to reach and sustain a high level. Short intervals can also achieve this when brief recoveries keep oxygen uptake elevated between efforts. The result therefore supports longer intervals as an option, without ruling out formats such as 30/15s. **Changing intensity within intervals also increased the oxygen response.** Compared with steady efforts, variable-intensity protocols added an average of approximately two minutes and 45 seconds near VO₂max. These included different approaches, such as fast starts and changes in power during longer reps. Results varied between studies; the average is not a guaranteed gain from adding surges to a workout. **The link to long-term improvement was less clear.** The review discussed training studies in which more time near VO₂max was associated with greater improvement, alongside studies where different amounts produced similar gains. It did not establish a universal five- or ten-minute minimum needed for a session to be effective. There are also measurement limits. Responses varied between riders and sessions, and results depended partly on how breathing data were processed. Time above 90% of maximum heart rate is not interchangeable with time above 90% of VO₂max. A heart-rate file cannot directly reproduce the laboratory measure used here. For coaching, the findings support using longer intervals when sustained aerobic demand is the objective. They provide less certainty about which format will produce the best adaptation for an individual rider. Recovery cost, weekly frequency and masters-specific prescriptions were not established by this review. What you do with this depends on which rider you are. **If you're time-capped:** consider longer reps for sessions aimed at your aerobic ceiling. Judge the amount of work you can complete consistently, rather than assuming shorter, harder efforts are automatically more efficient. **If you're over 50:** avoid adding reps solely to reach a supposed minimum number of red-zone minutes. There is no masters-specific target here. Consider recovery and your ability to repeat the training over several weeks. **If you're chasing a result, or facing a new event:** match the interval format to the demands you need to develop. Sustained efforts and repeated surges serve different purposes; a higher oxygen-uptake score alone does not establish better race preparation. Time near VO₂max helps describe a session's demand. Progress across the training block remains the more useful test of whether it worked. **Source.** Schoenmakers P, Murray K, White J, Matta G, Bossi AH. Time spent at or near VO₂max during high-intensity interval training - a systematic review and meta-analysis. _BMC Sports Science, Medicine and Rehabilitation_. 2026;18:358. [doi:10.1186/s13102-026-01766-x](https://doi.org/10.1186/s13102-026-01766-x). 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