Detraining: Loss of Training-Induced Physiological and Performance Adaptations. Part II [Article Review}
- Whistle Performance
- Jan 26
- 3 min read
This review covers Part II of Mujika and Padilla’s comprehensive analysis of detraining. While Part I focused on short-term breaks (under 4 weeks), this article was written to examine long-term detraining (cessation of training for more than 4 weeks). The authors aimed to detail exactly how the cardiovascular, metabolic, and muscular systems degrade over extended periods of inactivity in both highly trained athletes and recently trained individuals. Crucially, the article also reviews evidence-based strategies—such as reduced training and cross-training—to help athletes retain their hard-earned adaptations during injury, illness, or the off-season.
Key Takeaways and Results
The authors distinguish between "highly trained" athletes (who retain some baseline fitness above sedentary levels) and "recently trained" individuals (who often lose all gains).
• Cardiorespiratory Losses:
◦ VO2max declines significantly: In highly trained athletes, it drops by 6–20% but generally stabilizes at a level higher than sedentary controls. In recently trained individuals, VO2max gains are often completely reversed to pre-training levels.
◦ Heart Function: The loss of aerobic power is largely driven by a reduction in blood volume, which leads to decreased stroke volume and cardiac output, despite an increase in heart rate during exercise.
• Metabolic Changes:
◦ Fuel Utilization: The body becomes less efficient at burning fat. Athletes show an increased reliance on carbohydrates (higher respiratory exchange ratio) and a return of resting muscle glycogen to baseline levels.
◦ Lactate: The lactate threshold occurs at a lower percentage of VO2max, though in athletes, it remains better than in untrained individuals.
• Muscular and Strength Changes:
◦ Structure: Capillarization and arterial-venous oxygen difference decrease, contributing to the loss of aerobic power. Muscle fiber size decreases in strength athletes, and oxidative enzyme activity drops significantly (25–40%) in endurance athletes.
◦ Strength Retention: Force production declines much slower than endurance capabilities. Strength levels can drop by only 7–12% over 8 to 12 weeks of inactivity and usually remain above control values for very long periods.
Practical Application for Performance Coaches
If your athletes face a period of forced downtime (injury, travel, or off-season), you can prevent total detraining using these strategies:
1. Prioritize Intensity Over Volume: The most critical factor for retaining physiological adaptations is maintaining training intensity. You can reduce training volume by 60% to 90% and still maintain fitness, provided the intensity of the remaining sessions is kept high.
2. Moderate Frequency Reduction: While volume can be slashed, be careful with frequency. Athletes should reduce frequency by no more than 20–30%, whereas less trained clients can reduce frequency by up to 50% without significant losses.
3. Use Cross-Training:
◦ For highly trained athletes, cross-training is most effective if the mode of exercise is similar to their sport.
◦ For moderately trained individuals, even dissimilar training modes can effectively delay deconditioning.
4. Leverage the Cross-Transfer Effect: During rehabilitation for a unilateral injury (e.g., a cast on one leg), continue to train the healthy limb. The "cross-transfer effect" can help limit strength loss and atrophy in the injured, immobilized limb.
This research explores the physiological consequences of long-term detraining, defined as a period of insufficient physical stimulus exceeding four weeks. It highlights how cardiorespiratory capacity and metabolic efficiency decline significantly, though elite athletes often retain higher baseline levels than sedentary individuals. Muscular changes include reduced fiber size and lower oxidative enzyme activity, which directly impair endurance and strength over time. To counteract these losses, the authors recommend maintaining training intensity while strategically reducing volume and frequency. Additionally, the text suggests that cross-training and exercising unaffected limbs can help preserve fitness during injury or recovery periods. Overall, the findings emphasize that while inactivity reverses many gains, deliberate maintenance strategies can effectively mitigate the negative impacts of deconditioning.
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