Which sport is toughest?

Prince William enjoys water polo, but how fit do you need to be to play other demanding sports? Peta Bee puts a whole host of sports on the starting line and tells us which is the toughest. Results are listed in descending order.

1. Indoor/outdoor rowing

How challenging: The most physically demanding of all sports. You use both upper and lower body, pushing (with the legs) and pulling (with the arms) against a resistance. Hard work for the aerobic system and muscles.

Benefits: Works every major muscle group including legs, buttocks, shoulders and stomach. The machine doesn't jar the joints. Burns 450 calories per hour.

Downsides: It is difficult to keep going for long. And it can be boring.

2. Cross-country skiing

How challenging: Widely considered one of the toughest physical activities. It pushes arms, legs and aerobic system to the limit.

Benefits: Burns 400 calories an hour and gives well-toned, but not bulky, legs. Sliding motion of skis means it's kinder on knees than running.

Downsides: Unless you live in the Alps you'll need a machine.

3. Water polo

How challenging: Very. You need to be a strong swimmer as you are constantly treading water. Good aerobic fitness required.

Benefits: Develops strong leg and stomach muscles and arms, to a lesser extent. Good aerobically.

Downsides: Games last only 20 minutes which means you burn only 150 calories in total.

4. Running

How challenging: Difficulty increases the faster and further you run. Made more challenging by varying terrain and adding hills.

Benefits: Excellent for increasing aerobic capacity and strengthening bones. You'll also tone muscles like the gluteus maximus in your bottom, iliopsoas muscles in your hips and hamstring muscles. Burns 490 calories an hour (10-minute-miles).

Downsides: With every stride, the force of three times your body weight reverberates through the legs and spine. Not good for joints.

5. Swimming

How challenging: Water is one thousand times denser than air and provides up to 12 times the resistance that you would get from working out on land - which makes swimming hard work.

Benefits: A few lengths of swimming any stroke, however slowly, will call on all the major muscles to propel you through the water. Uses upper and lower body equally. Excellent aerobic workout uses up 465 calories an hour for front crawl.

Downsides: Doesn't strengthen the bones. Chlorine in pools recently linked to asthma.

6. Cycling

How challenging: A lot depends on the environment. Freewheeling downhill is easy; pedalling on undulating terrain is a tough workout.

Benefits: Burns around 385 calories an hour if you pedal 10 miles in that time. Strengthens muscles in the legs and the buttocks as well as improving cardiovascular function. Low impact - so better for the knees than jogging.

Downsides: Doesn't work the upper body and won't strengthen the bones.

7. Boxing

How challenging: You have to be aerobically fit and your flexibility, strength and reaction times are tested to their limits. Boxercise-style classes address every aspect of fitness training

Benefits: All the major muscles are used, as well as heart and lungs. A circuit with sparring and skipping can eat 450 calories an hour. Because it reduces feelings of aggression, it is often used in anger management.

Downsides: You need good peripheral vision, reactions and awareness to risk of serious injury.

8. Squash

How challenging: Less stopping and starting than in tennis so you need a good level of aerobic fitness to play.

Benefits: Very aerobic - good for building an endurance base. Plenty of lunging for the ball tones the leg and bottom muscles. Also works the abdominal muscles which control your posture.

Downsides: Twisting is bad for old injuries and vulnerable joints.

9. Skipping

How challenging: Exhausting. It is difficult to skip for long enough to benefit fitness-wise.

Benefits: Excellent aerobic exercise. Twenty skips five times a day will subject your spine and hips to 100 high-impact jolts and prevent thinning of your bones. Can burn 390 calories an hour.

Downsides: Boring. Not good for back problems or weak joints.

10. Football

How challenging: Premiership players cover around 6.5 miles in a match. At any level, it is aerobically and anaerobically tough.

Benefits: Improved speed, stamina, explosive power and flexibility. You'll develop spatial awareness, better balance, and burn 360 calories an hour.

Downsides: Postural imbalances can occur if you favour kicking with one foot. Unless you are a goalkeeper, you don't use your arms at all.

11. Rugby

How challenging: Like football, rugby involves plenty of jogging interspersed with sprinting, so you need to be fit.

Benefits: Rugby players have strong upper bodies. Playing uses up 380 calories an hour and gives all-over conditioning, speed, endurance, explosive power and flexibility.

Downsides: There is a high risk of injury. And because strength is an advantage in certain positions, some players tend to bulk up.

12. Tennis

How challenging: Depends on ability. There can be a lot of stopping and starting so there's plenty of time to get your breath. Need a good level of aerobic fitness before you start playing.

Benefits: Develops speed and power in the legs. Also improves co-ordination, agility and flexibility.

Downsides: In doubles you share the workload so burn fewer calories (250 per hour compared with 400 in a singles match).

13. Snowboarding

How challenging: Mastering the technique is the biggest challenges.

Benefits: Improves all-over strength, balance and flexibility. Strong stomach and arm muscles are important for getting up from and preventing falls. Eats up 240 calories an hour.

Downsides: Not a good aerobic workout. Injuries are common.

14. Ice skating

How challenging: Balance is the biggest challenge to beginners.

Benefits: Skating is great for firming the buttocks (you use the gluteal muscles to propel you forward). You can make skating more difficult by incorporating manoeuvres and squats which tone the legs. Burns 240 calories an hour. Carry weights to work arms.

Downsides: Freewheeling along isn't much of a workout at all. Unless you include hills and inclines, your heart won't be working hard enough to produce an aerobic benefit.

15. Golf

How challenging: In fitness terms, not very. But technically it could take years to master your swing.

Benefits: Improved concentration, trunk strength and upper body flexibility. Walking around the course is also good aerobic exercise although, on average, you only burn around 300 calories an hour during a round.

Downsides: You overuse one side of the body which can cause problems. Seve Ballesteros and Colin Montgomerie suffer back pain after years of hitting golf balls in the same way.

16. Horse riding

How challenging: Learning how to control the horse is the hardest part.

Benefits: Regular riding results in stronger buttock, thigh and trunk muscles without necessarily adding bulk. The adductor muscles of the inner thigh that grip the horse work the hardest. Riding will improve posture - and it won't give you a big bottom. Trotting along you will burn about 285 calories an hour.

Downsides: Doesn't offer much aerobically (mucking out is the best way to burn calories).