What's the minimum amount of exercise to maintain VO2max as I age?

VO2max can be maintained for 10–15 weeks after cessation of training with approximately 2 days per week of aerobic exercise at the previously trained frequency's intensity, the critical variable for maintenance is intensity (how hard you are working), not volume (how many minutes), suggesting that for men whose schedule limits training, 2 higher-intensity sessions per week preserve fitness better than 5 low-intensity sessions (Mujika & Padilla, Med Sci Sports Exerc, 2000).

The detraining literature is clear: VO2max begins to decline within 2–4 weeks of complete cessation, with 5–12% decline in the first 2–4 weeks. The good news is that "muscle memory" (epigenetic and structural adaptations in trained muscle) allows faster re-training after a layoff, a man who was fit at 35 and detrains until 42 will re-reach his prior fitness faster than a man who has never trained. The minimum effective maintenance dose for men with demanding schedules: 2 sessions per week, one zone 2 (35–40 minutes) and one HIIT (4×4 protocol), totaling approximately 90 minutes per week of quality training.

Honesty Scale: Solid (1) for the detraining timeline and intensity-priority principle for fitness maintenance.

What to do: If you cannot maintain your ideal training volume due to travel or work demands, protect the intensity of 2 sessions rather than doing 5 reduced-intensity sessions. A 35-minute zone 2 session and one HIIT session per week is the minimum I would prescribe for a patient prioritizing cardiovascular fitness maintenance.

For the full picture, read The VO2max/Zone 2 Deep Dive