Individuals with a higher proportion of fast-twitch muscle fibers require longer recovery periods.
Last updated on June 25th, 2025
Recovery is when muscles repair, replenish energy stores, and adapt to the physical demands of training. This process boosts athletic performance, promotes muscle growth, and builds strength (1). Yet, even with proper recovery strategies, many athletes still experience fatigue during training.
Dr. Gommaar D’Hulst, founder of WOD Science and senior scientist at ETH Zurich, Switzerland, explored the latest research on improving recovery, addressing threee aspects of recovery:
Glycogen
Glycogen, a stored form of glucose energy, is primarily found in the liver and muscles and is vital in fueling high-intensity activities, such as HYROX or CrossFit. The more intense the exercise, the faster glycogen is depleted.
During the first hour of training, glycogen synthesis occurs rapidly, but fully replenishing these stores can take 24 to 48 hours. Starting a workout with low glycogen levels can significantly impact performance and recovery. Maintaining adequate glycogen reserves is crucial for achieving optimal results and supporting recovery.
Muscle Soreness
Muscle soreness, also known as delayed-onset muscle soreness (DOMS), typically peaks 24 to 48 hours after exercise, depending on the muscle groups involved. While it gradually subsides, it can take three to four days to disappear, often impacting recovery.
Performance
Performance is a meaningful factor in the recovery process. Scientists measure performance in various ways, such as assessing how high an individual can jump from a standstill or evaluating maximal voluntary contractions using a leg extension machine.
Performance declines after training and requires a specific amount of time — varying by muscle group — to recover fully.
You can be sore and glycogen levels can be reduced, but end recovery is predominantly determined by performance.
—Dr. Gommaar D’Hulst
Training Intensity & Recovery: Latest Research
This study investigated the impact of training intensity on recovery in athletes. The research involved 14 professional cyclists from South Africa, all with a critical power and aerobic threshold of 5.4 watts per kilogram of body mass. (2)
In the study’s first phase, participants underwent a power profile test to establish their baseline performance. During the second phase, they completed a fatiguing protocol at 70% of their critical power, maintaining this lower intensity until they expended exactly 200 kJ of energy.
On a different day, participants performed a high-intensity interval training (HIIT) session, which included five eight-minute intervals, each followed by eight minutes of recovery or light cycling.
For the third phase, participants performed a post-fatigue power profile test, identical in structure to the baseline test. This assessment was conducted 72 hours after completing each fatiguing protocol to evaluate their recovery and performance.
When participants performed a 15-second all-out sprint in a rested state, they generated an average power output of 900-920 watts. After low-intensity exercise, performance slightly declined. However, a substantial drop in power output was observed in a fatigued state — 72 hours after high-intensity exertion — compared to the fresh state.
These findings highlight the significant impact of training intensity on recovery. Researchers explored individual responses to varying training intensities, discovering that some participants were more resistant to fatigue and better at maintaining sprint performance than others.
Muscle Fiber Type & Recovery
Muscle fiber typology can be assessed by analyzing carnosine levels. (3) The relative concentration of carnosine within a muscle can be measured using MRI technology. Since type II muscle fibers, responsible for explosive, fast-twitch movements, contain higher levels of carnosine, this data allows for estimating muscle fiber composition.
During the study, participants underwent performance tests after each training period. Their recovery and performance noticeably declined when they were overtrained compared to when they were well-rested.
Notably, those exhibiting the greatest performance-related fatigue were found to have a higher proportion of type II muscle fibers. This suggests that athletes with predominantly fast-twitch muscles require longer recovery following high-intensity efforts.
Take Home
- Intense training extends required recovery time, especially for short, high-power efforts.
- To accumulate training volume, lower the intensity, and progressively build, resulting in faster recovery and more training.
- A person’s physique and genetics are significant for determining recovery after intense exercise.
More In Research
References
- Bishop, P. A., Jones, E., & Woods, A. K. (2008). Recovery from training: a brief review: brief review. Journal of strength and conditioning research, 22(3), 1015–1024. https://doi.org/10.1519/JSC.0b013e31816eb518
- Spragg, J., Leo, P., Giorgi, A., Gonzalez, B. M., & Swart, J. (2024). The intensity rather than the quantity of prior work determines the subsequent downward shift in the power duration relationship in professional cyclists. European Journal of Sport Science, 24(4), 449–457. https://doi.org/10.1002/ejsc.12077
- Bellinger, P., Desbrow, B., Derave, W., Lievens, E., Irwin, C., Sabapathy, S., Kennedy, B., Craven, J., Pennell, E., Rice, H., & Minahan, C. (2020). Muscle fiber typology is associated with the incidence of overreaching in response to overload training. Journal of applied physiology (Bethesda, Md. : 1985), 129(4), 823–836. https://doi.org/10.1152/japplphysiol.00314.2020
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