LISTEN TO YOUR HEART
Most interval programmes use the clock; you work for 30 to 60 seconds and then recover for twice that. There’s a smarter way, says Alwyn Cosgrove.
ACCELERATE TO 85 The type of exercise doesn’t matter. Run, ride, swim, swing a kettlebell, dance. Determine your work and rest by your heart rate. Build up to 85% of your max heart rate; it should feel like hard work.
DECELERATE TO 70 Slow down to 70% until your breathing recovers. With each interval, the scant recovery builds an oxygen deficit. Your heart and lungs have to work extra-hard to restore oxygen levels.