I stopped for 3 months at 53 — how much did I lose?
One trained triathlete lost 7% of VO2max (9% per kg) and 10% of peak power in 12 weeks off, and 12 weeks back (full volume by week 7) restored it. n = 1; one test per point.
Zanou et al. followed a 53-year-old French triathlete who had trained without a break of more than 2 weeks for 20 years (about 500 h a year: 120 h swimming, 270 h cycling, 110 h running) and decided to stop after a 10-h swimrun race in September 2022. For 12 weeks he did no structured exercise beyond two slow 30-min walks at weekends and two 15-min core sessions a week.
He then retrained for 12 weeks, from about 50% of his usual volume to 100% by week 7 (10-12 h a week), adding more high-intensity sessions than before the break, especially in the third month.
Absolute VO2max on a cycle ergometer fell from 4.58 to 4.27 L/min (−7%) and rose to 4.81 L/min after retraining (+5% vs baseline); body mass moved 74.0 → 76.1 → 73.1 kg, so relative VO2max went 62.0 → 56.2 (−9%) → 65.8 mL/kg/min (+6%). Peak power went 375 → 338 (−10%) → 388 W (+3%).
In single vastus lateralis biopsies, detraining raised fast-myosin (+42%), SERCA1 (+138%) and RyR1 (+44%) protein and lowered PGC-1α (−19%), most respiratory-chain complexes and SOD2 (−30%); after retraining PGC-1α, respiratory-chain complexes, SOD2, GLUT4 (+36%) and hexokinase II (+100%) were above baseline.
The authors note his VO2max loss was at the low end of the 11-20% reported in older endurance athletes after 12 weeks off, and that the break "was beneficial" to boost his phenotype after retraining.
Our reading: one man, one measurement per point, and a retraining block with more intensity than his pre-race block, which was mainly long, slow- and medium-intensity preparation for a 10-h race; the gain above baseline cannot be credited to the break itself, as the authors partly concede.
Protocol
Design: single case, three test points: Pre (in the 2 weeks before the final race on 5 September 2022), after 12 weeks of detraining (retest in week 13), after 12 weeks of retraining. Ethics approval CER-VD 2022-01614 (Lausanne); written consent. "As a university researcher, he planned the whole experiment with his colleagues"; the paper does not say whether he is a co-author.
Who: man, 53, triathlon since 20; 74.0 kg at baseline; in the 3 months before the break 10.8 h/week (32% swim, 38% bike, 30% run), mostly long, slow and medium-intensity training for a ~10-h swimrun (10 km swimming, 65 km trail running; 42nd in the men's team category in 10 h 01 min).
Detraining: 12 weeks of no structured exercise and minimal daily activity, apart from two slow 30-min weekend walks and two 15-min core sessions (planks, side bends, hip dips) per week.
Retraining: 12 weeks, progressing from about 50% to 100% of usual volume over 6 weeks and at full volume (10-12 h/week) from week 7; 28% swim, 47% bike, 25% run; more high-intensity sessions than at baseline, especially in month 3; total volume "about the same" as before the break.
VO2max: electrically braked cycle ergometer (Lode Excalibur); 2 min at 100 W, then +25 W every 2 min to exhaustion; COSMED K5 portable analyser; peak power = highest 2-min stage completed, prorated for a partial stage. One test per time point; no verification bout or repeat.
Muscle: needle biopsy of the left vastus lateralis (three ~15-mg samples from one puncture) at each point; western blots for calcium-handling, myosin, mitochondrial biogenesis, dynamics, respiratory-chain, antioxidant and glycolytic proteins, normalised to total protein and expressed as % of Pre; two independent blots per protein, averaged. No fibre typing, no enzyme activities, no statistics.
Comparators: none measured; literature values for detraining in young and older endurance athletes.
Funding: University of Lausanne support to three authors (NZ, VG, NP); no competing interests declared.
Key Results
| Measure | Pre | After 12 wk detraining | After 12 wk retraining |
|---|---|---|---|
| Absolute VO2max | 4.58 L/min | 4.27 L/min (−7%) | 4.81 L/min (+5.0% vs Pre) |
| Relative VO2max | 62.0 mL/kg/min | 56.2 (−9%) | 65.8 (+6% vs Pre) |
| Peak power output | 375 W | 338 W (−10%) | 388 W (+3% vs Pre) |
| Body mass | 74.0 kg | 76.1 kg | 73.1 kg |
| Muscle protein (western blot, % change vs Pre) | Detraining | Retraining |
|---|---|---|
| RyR1 (calcium release channel) | +44% | +3% |
| FKBP12 (RyR1 stabiliser) | −24% | not recovered |
| SERCA1 (fast-fibre calcium pump) | +138% | −5% |
| SERCA2 | −7% | +14% |
| Fast myosin heavy chain | +42% | +14% |
| Slow myosin heavy chain | +16% | +14% |
| PGC-1α (mitochondrial biogenesis) | −19% | +16% |
| OPA1 / Mfn2 / DRP1 (mitochondrial dynamics) | +17% / +31% / +42% | +64% / +81% / +96% |
| Respiratory-chain complexes I, III, IV, V | −10%, −8%, −13%, −3% | +10%, +24%, +20%, +28% |
| SOD2 (mitochondrial antioxidant) | −30% | +66% |
| Catalase | −48% | −29% |
| GLUT4 / hexokinase II | +10% / −11% | +36% / +100% |
Performance: a 7% (absolute) to 9% (relative) loss of VO2max after 12 weeks off, recovered and exceeded after 12 weeks back; the authors place the loss in "the lower range" of the 11-20% reported for older endurance athletes after 12 weeks, though 7-9% is below that range.
Muscle: detraining shifted protein levels towards a fast-fibre, less oxidative profile; retraining reversed most of this and took mitochondrial and glycolytic proteins above baseline. Fibre type itself was not measured.
Mechanisms
Measured: the protein shifts above, in single biopsies with no measure of variability; enzyme activity and mitochondrial function were not measured ("even though not measured in this study").
Authors' interpretation: a long aerobic training history "does not protect muscle cells" against 12 weeks off; detraining "triggered mitochondrial dynamics, possibly to prepare the muscle cells for better aerobic adaptations in case of retraining".
Authors' interpretation: the 5% VO2max gain above baseline may reflect the changed training content ("we cannot exclude that the small changes in training modalities") or that the break "boosted the physiological effects of training". The conclusion then calls the break "beneficial".
Inference: the baseline test came at the end of race-specific preparation for a 10-h race (mainly long, slow- and medium-intensity work) and the final test after a block with more high-intensity work and more cycling (47% vs 38%), on a cycling test. More intensity and more bike work before a bike test predict a higher bike VO2max and power by themselves; the design cannot isolate a "rebound" from the break.
Inference: a western blot change of 10-30% in one biopsy per time point is within the range of sampling and blot variability; only the large shifts (SERCA1 +138%, hexokinase +100%, DRP1 +96%) are plausibly more than noise, and even those are single values.
Practical Application
I stopped for 3 months at 53 — how much did I lose? One trained triathlete lost 7% of VO2max (9% per kg) and 10% of peak power in 12 weeks off, and 12 weeks back (full volume by week 7) restored it. n = 1; one test per point.
For a masters athlete after a long break: this case agrees with the base's detraining review that losses after about two months off sit around 10-20% and then level off (REF-1133, B+), with this man at or below the low end (7% absolute, 9% per kg after 12 weeks). Rebuild volume over about 6 weeks, as he did (practice, one case), and see SYNTH-36 for how the reason for the break changes the return.
Do not plan a break to "come back stronger". The rise above baseline came with more high-intensity and more bike training before a bike test; the authors cannot exclude that the change of training explains it. The base's position is that a planned break costs fitness that must be rebuilt (SYNTH-36).
Muscle changes run ahead of the performance numbers (one case): muscle proteins shifted further than VO2max during the break, and the authors suggest cardiorespiratory function recovers faster than muscle. That is a hypothesis from single biopsies, not a timeline for return.
Limitations
One man; one VO2max test and one biopsy per time point; no repeat test, so day-to-day variation (often a few percent for VO2max) is unknown here.
The subject planned the experiment with his colleagues; no blinding of anyone; the paper does not say whether he is an author.
The retraining block differed from the baseline block (more high intensity, more cycling, a different season), so the post-retraining values are not a clean comparison with baseline; the authors acknowledge they cannot exclude this.
Baseline was taken in the 2 weeks before a 10-h race, at the end of mainly long, slow- and medium-intensity race preparation; the VO2max test was on a bike although he trained across three sports.
No statistics on any outcome; protein data are western blots of single biopsies (two blots averaged), with no fibre typing, enzyme activity or mitochondrial respiration.
Internal inconsistency: relative VO2max fell 9% by the Results figures (62.0 → 56.2) but "~10%" in the Discussion.
The conclusion that the 12-week break "was beneficial" goes further than one uncontrolled case with a changed training mix supports (our reading).
Funding: University of Lausanne support to three of the four authors; no competing interests declared.
How this entry was checked and changed
Why this level
single case study (the rubric's row for n = 1), read from the full text (Wiley Online Library, open access). One test per time point, no repeat to estimate day-to-day noise, no statistics on the protein data, and the subject planned the experiment with his colleagues
Full text (checked 2026-10-22)
53-year-old French Caucasian; triathlon since 20 years old; "no complete break for more than 2 weeks in a row each year"; about 500 h per year (120-h swimming, 270-h cycling, and 110-h running) (full text).
During detraining he "walked twice for 30 min on the weekend at a slow pace and performed twice 15 min of core training"; retraining progressed "from approximately 50% of his usual training volume to 100% over the next 6 weeks"; by the 7th week 10–12 h per week (full text).
Before the break 10.8 h per week, 32% swimming, 38% cycling, and 30% running; retraining 28% swimming, 47% cycling, and 25% running; "the participant incorporated more high-intensity training sessions, especially during the third month" (full text).
Absolute VO2max decreased from 4.58 to 4.27 L min−1 (−7%) and increased to 4.81 L min−1, 5.0% greater than baseline; body mass 74.0 to 76.1 kg and to 73.1 kg; 62.0 to 56.2 mL kg−1 min−1 (−9%) and 65.8 mL kg−1 min−1 (+6% compared with baseline) (full text).
Peak power output 375 W, 338 W (−10%), and 388 W (+3% compared with baseline) (full text).
RyR1 44% increase, only 3% higher than baseline after retraining; FKBP12 (−24%); SERCA1 (+138%), (−5% compared with baseline); fast MHC increased by 42%, (+14% compared with baseline) (full text).
PGC-1α 19% decrease, then 16% increase; OPA1, Mfn2, DRP1 (+17, +31%, and +42%) and (+64%, +81%, and +96%); SOD2 depressed by 30%, then (+66% compared with baseline); catalase decreased by 48%, (−29% compared with baseline); Glut-4 and HK II upregulated by 36% and 100% (full text).
"we cannot exclude that the small changes in training modalities at retraining compared with before baseline may have played a role in this improvement" (full text).
Older endurance athletes after 12 weeks of detraining "showed a reduction ranging from 11 to 20%"; the relative decrease described as "by ~10%" in the Discussion (full text).
"Two independent blots were performed for each protein detection, and the average of the quantifications was represented in the graphs" (full text).