What is zone 5 training and should men over 40 do it?

Zone 5 training (above 90% of maximum heart rate, supramaximal effort) is used in VO2max development protocols (the Norwegian 4×4 method) and produces the largest acute stimulus for cardiac output ceiling improvement, it is appropriate for men over 40 who have established an aerobic base, have been screened for cardiovascular contraindications, and structure it as no more than 1–2 sessions per week within an otherwise zone 2-dominant program (Helgerud et al., Med Sci Sports Exerc, 2007).

The cardiovascular risk of high-intensity exercise in unscreened men over 40 is worth acknowledging directly. Vigorous exercise transiently increases the risk of a cardiac event in the hour during and after the effort, this risk is highest in men who are sedentary and suddenly engage in maximal effort. Men who exercise regularly at moderate intensity are at no elevated acute cardiac risk during high-intensity sessions. The prescription: build 12+ weeks of zone 2 base before adding zone 5 intervals, and if you have uncontrolled hypertension, known coronary artery disease, or significant cardiovascular risk factors, discuss this with a cardiologist before starting high-intensity training.

Honesty Scale: Solid (1) for zone 5 training's VO2max-improvement effect. Solid (1) for the risk stratification requirement before high-intensity training in men over 40.

What to do: Before starting any HIIT program over 40, take the PAR-Q (Physical Activity Readiness Questionnaire, freely available online), 7 questions that screen for conditions requiring physician clearance before vigorous exercise. If any questions trigger a "yes," see your physician before starting.

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