VO2 max measures the maximum rate of oxygen that the body can utilize during exertion. This value, expressed in milliliters per minute per kilogram of body weight, serves as a reference to assess aerobic capacity. Improving VO2 max does not rely on a single type of session: several physiological levers come into play, and some remain underutilized in traditional programs.
Unilateral strength and VO2 max: the often-overlooked link
Protocols for improving VO2 max almost always focus on cardio-respiratory training. The logic seems clear: to consume more oxygen, one must train the heart and lungs. Several recent coaching reviews nuance this approach.
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The problem sometimes lies downstream. If the muscles of the lower limbs fatigue before the cardio-respiratory system reaches its limit, the actual VO2 max is never fully expressed. The body has an aerobic capacity that it cannot exploit due to insufficient muscular support.
Heavy unilateral strength training (single-leg press, loaded lunge) targets this imbalance. The goal is not hypertrophy but the ability of each leg to sustain effort without giving out. As detailed in articles from the Carnet de Sportive site, the complementarity between strength training and aerobic work conditions progress on the field.
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This type of strength training is integrated outside of high-intensity sessions, typically twice a week, using heavy loads and short repetitions.
Training in controlled heat: a documented protocol for plasma volume
Exposure to heat during training has been the subject of recent studies. The main mechanism involves increasing plasma volume: blood carries more oxygen per heartbeat, which raises VO2 max without changing the intensity of the effort.
Protocols of ten to fourteen days of heat training, combined with a polarized approach (alternating easy sessions with very intense sessions), show results on aerobic capacity. This method remains demanding: it requires monitoring hydration, gradual adaptation, and control of ambient temperature.
The available data do not allow for conclusions about the exact extent of the gain for each athlete profile. Field feedback varies on this point depending on the initial level and the discipline practiced. However, the physiological principle (increased plasma volume) is widely accepted in recent reviews.
Carbohydrate periodization: training metabolism without sabotaging intensity
The “train low, race high” strategy involves conducting certain endurance sessions with limited carbohydrate intake, then restoring full intake for high-intensity sessions and competition. The goal is to improve metabolic flexibility and running economy.
VO2 max and threshold sessions should never be performed with restricted carbohydrates. This is the nuance that traditional nutritional advice often overlooks. Depriving the body of carbohydrates during intense intervals degrades the quality of the session and limits the cardio-respiratory stimulus.
A block of four weeks with some low-intensity endurance sessions done fasted or with reduced intake may be sufficient to provoke adaptations. The criteria to respect include:
- Reserve restriction for long, moderate-pace outings, never for sessions above the threshold
- Maintain normal hydration and electrolyte intake during these sessions
- Return to full carbohydrate intake at least 48 hours before any intense session or competition
Long-duration endurance: measurable gains beyond running
Recent meta-analyses on prolonged endurance (trekking, multi-week hiking) document an average increase in VO2 max of about 16% after programs lasting more than twenty weeks. This figure pertains to activities at moderate intensity, far from typical interval protocols.
This result questions the exclusive place given to intervals in performance-oriented training plans. For a practitioner who does not run or who is returning after a long break, accumulating volume at low intensity over several months produces significant aerobic adaptations.
Mountain hiking or trekking engages the cardio-respiratory system for durations that running makes difficult to sustain for a beginner. The joint constraints are lower, and the effort remains sufficiently prolonged to stimulate central adaptations (stroke volume, capillarization).
Structuring VO2 max sessions: concrete guidelines
For practitioners integrating specific sessions, the short interval format remains the most documented. Sessions like 4×4 minutes at high intensity, interspersed with active recoveries, directly target the maximum capacity for oxygen utilization.
Key points to watch for in these sessions:
- The intensity should reach a pace close to the maximum aerobic speed, maintained throughout each interval without collapsing at the end of the block
- The recovery between intervals remains active (walking or light jogging) to maintain a high heart rate
- The weekly frequency is limited to one or two sessions of this type, with the rest of the volume dedicated to fundamental endurance
- The body needs 48 to 72 hours of recovery after a VO2 max session before doing another
The alternation between intense sessions and low-intensity volume corresponds to the polarized model, where the majority of training time is spent at low intensity and a reduced fraction focuses on efforts close to the maximum.
VO2 max progression slows with the athlete’s level. A beginner may observe rapid gains over a few weeks, while a trained athlete will need to combine several levers (strength, heat, nutritional periodization, volume) to continue progressing. No single protocol works indefinitely, and the variety of stimuli remains the best tool to push past plateaus.