To paraphrase a business-school platitude: sometimes you've got to spend some to make some. But – as with money – invest your energy in the wrong places and you're set for a crash. If your week is looking more hectic than Wembley Way on Cup final day, forget smashing the gym for an hour in hopes of coming out on an endorphin high. Instead, opt for a 20-minute dawdle around the floor and you'll find you actually boost energy. Crucially, you don't need to cram your entire workout into fewer minutes: the University of Georgia found that low-intensity exercises (working at 40% of your VO2 max, typically around 120mph) have a positive effect on your nervous system, which increases energy production without burning you out. Not going hard or home reduces fatigue by 65%, buying you more vim and vitality. Instead of squatting your max weight, lighten the load and take long breaks between sets to give you a natural boost. It's something for nothing.

Take it down a level

Try these activities recommended by PT Daryl Browne to keep your bpm at 120 for 20 minutes.

Hatha Yoga

The combination of fluid movements and focus on breathing means your heart rate stays constant, which optimises your energy gains.

Park Life

Spend Sundays throwing a ball about in the park. Simply squeezing a tennis ball before lobbing it boosts grip for free-weight training.

Table Tennis

The key to winning at ping pong is to focus on the space between you and your opponent, not the ball – it improves cognitive function.

Photo: Getty