VO2 max is the maximum amount of oxygen your body can take in, transport and use per minute. Watch estimates can be 10-15% off; a laboratory test with breath-by-breath gas analysis gives the real value plus ventilatory thresholds VT1 and VT2. Build an aerobic base, add 4-6 x 3-5 minute intervals at 90-95% of max heart rate, keep threshold work and recover deliberately for 10-20% gains in 8-12 weeks.
VO2 max sets the ceiling on your endurance. A higher value means you recover faster between sprints. Football players feel it late in a match. Runners feel it on the last climb. It is not the only thing that matters, but it is a good place to start.
A watch estimate can be off by ten to fifteen percent. A lab test measures every breath instead. It also gives your two ventilatory thresholds. Those set the zones you will actually train in. Retest after eight to twelve weeks.
Build a big easy base first. Most of your week should feel comfortable. Then add four to six intervals of three to five minutes near your top effort. Keep one threshold session. Sleep well and eat enough. Gains of ten to twenty percent are normal.
