Detraining

Detraining is the partial or complete loss of training adaptations when the training stimulus becomes insufficient.^{1Mujika and Padilla, Detraining, Part I, p. 1.} This is the reversibility principle: stop or sharply reduce training and adaptations begin to reverse.^{1Mujika and Padilla, Detraining, Part I, p. 1.} A taper has a different purpose, cutting volume, usually duration and frequency rather than intensity, to improve performance.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 146.}

Aerobic adaptations are the most sensitive to time off.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 146.} In highly trained athletes, maximal oxygen uptake (VO2 max) falls 4% to 14% with short-term detraining (about four weeks) and 6% to 20% with longer breaks.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 146.} Strength holds up better: in the first four weeks, muscle fiber size gains reverse but strength declines are limited.^{1Mujika and Padilla, Detraining, Part I, p. 1.}

In practice

• Keep training intensity during a busy period: volume can drop by 60% to 90% if intensity holds.^{3Mujika and Padilla, Detraining, Part II, p. 7.}
• Cut training frequency more cautiously, by no more than 20% to 30% in athletes and up to 50% in less trained clients.^{3Mujika and Padilla, Detraining, Part II, p. 7.}
• Use cross-training when needed: similar exercise modes can slow detraining in athletes, and even dissimilar ones may help moderately trained clients.^{3Mujika and Padilla, Detraining, Part II, p. 7.}
• Reassure returning clients that someone who got strong once tends to respond faster on returning than they did as a beginner.^{4Rippetoe et al., Practical Programming for Strength Training, 3rd ed., p. 108.}