Hard (RPE:* an 8 or 9 out of 10)
An air bike. Gyms such as Triplefit, Virgin Active, Pure Fitness and Fitness First have them. Ask a trainer to point one out.
HOW IT WORKS
Start with the warm-up. Then complete 12 rounds of alternating 40 seconds on the bike (shoot for an effort level of 250 watts or better) with 40 seconds of body-weight strength exercises, taking 20 seconds to transition between each round.
211 (this calorie burn is based on a 63.5kg woman). *Rate of perceived exertion; see www.shape.com.sg/rpe