Swimming pools were once a haven for two types of person: the goggle-clad who thrashed out monotonous lengths and the flowery-capped seniors who performed gentle, aerobic-type jumps and twists in a cordoned-off area of the water. Now, though, the fitness-savvy have decided the pool can be cool, provided the activities on offer are as appealing and varied as those available at the gym. "There has definitely been a change in the pool's image," says Rob Beale, swimming manager at Virgin Active gyms. "Now a lot of the younger crowd are keen to try land-based workouts that have been transferred to the water."
There are unquestionable benefits to working out in the pool. Water is 1,000 times denser than air and provides up to 12 times the resistance you would get from working out on land. "A workout in the pool therefore requires you to work harder and expend more energy than you would normally," says Beale.
For people with joint and back problems, aqua-workouts are ideal - a body submerged at rib cage depth weighs about 75% less than it would on land, and approximately 90% less when submerged to the neck, meaning that water acts as a giant cushion for the joints, protecting them from the kind of stress and impact they experience when exercising out of the water.
Many workout fads emanate from America and there, this summer, aqua-fitness is all the rage with aqua-abs, splash kickboxing and aqua-cross training all appearing on gym timetables. But what's on offer here?
What it is: Wearing a specially-designed "aqua-jogger" buoyancy vest over your swimwear, the idea is to simulate a running action in deep water so there is none of the stress to your joints.
Benefits: This activity was originally devised by physiotherapists in the 1980s to help rehabilitate injured athletes. "In general, water is cooler than body temperature which means that people have to work harder to stay warm," says personal trainer Cornel Chin. "The best thing is it doesn't require any particular skill. Even people who can't swim can do it." Run on land and you can expect to burn around eight calories a minute; in water, that figure rises to 11.5 calories for the same time.
Find out more: Several London boroughs rope off lanes of their pools at set times for aqua- jogging. The website aquajogger.com provides plenty of information on how to get started. To purchase an aqua-jogger belt (from £38), visit londonmarathonstore.com.
What it is: A combination of the principles of water fitness and the graceful flowing movements of Tai Chi, performed upright in chest-depth water. Do not expect lots of thrashing around and treading water - as with the traditional, land-based version of this ancient art form, the movements are performed s-l-o-w-l-y and with precision. Emphasis is on good balance and coordination with a definite bias towards strengthening mind as well as body.
Benefits: Tai Chi has been shown in studies to have beneficial effects on everything from stress and increased blood pressure to high cholesterol levels. An Australian study published this month in the medical journal Arthritis & Rheumatism revealed that a combination of hydrotherapy (or water treatment) and Tai Chi can help older people with severe arthritis to move and feel better and experience significantly less pain in their hips and knees.
Find out more: Many gym chains hold their own versions of this class (also called Water Chi and Pool Chi). Contact the Tai Chi Union of Great Britain (taichiunion.com) for teachers who specialise in water-based instruction.
What it is: A unique, British-designed system that is lowered into a pool and attached to walls by giant suction pads. For the gym-coy, the beauty of the equipment - including a semi-sub-aqua rowing machine, step-climber, chest press and exercise bike - is undoubtedly the fact that only your head remains visible as you exercise.
Benefits: Unlike conventional gyms, this one has no weights, only plastic floats to pull through the water. However, since water itself provides natural resistance, it provides a great form of low-impact strength training. It is widely used in hospitals as rehabilitation equipment for patients who have suffered heart disease or strokes. "An aqua-gym circuit can be very tough as it is recommended to jog from each piece of equipment to the next to maintain your body temperature," says Dean Hodgkin, fitness director of Ragdale Hall in Leicestershire. "It is a great alternative to conventional weight training for people who have problem joints or who just feel self-conscious using a weights room at the gym."
What it is: A current hit in New York's gyms, this is a fusion of Pilates and water fitness that aims principally to strengthen your core abdominal muscles. However, the buoyancy and resistance of the water means that other muscles are worked harder than usual too.
Benefits: Beyond fitness, Pilates has many preventative benefits for a range of common ailments. Back pain, for instance, is often triggered when your body is pulled out of alignment: Pilates helps to pull it back by strengthening the core muscles around your lower back and stomach. Studies at Queensland University in Australia have shown that Pilates exercises can develop the muscles that support the back. It is much more effective for preventing back pain than yoga. Since the water provides extra cushioning, the pool-based class is said to be at least as beneficial, although many teachers of the traditional method pooh-pooh Poolates as a gym fad.
Find out more: Check with your gym or local authority pool where Poolates or Waterlates classes are springing up. Or visit poolates.co.uk for general information.
What it is: As its name suggests, this is a programme to help those who like swimming to get the most out of their lengths in the pool. It includes drills such as using a kickboard in your hands at arm's length to work your legs or, to work your arms, holding the kickboard between your feet. This particular programme is being launched at DC Leisure gyms (ie those run by local authorities) although Virgin Active is working with the Amateur Swimming Association to launch a similar plan.
Benefits: Swimming is generally regarded as the best all-round fitness activity as it works all the body's major muscle groups and has an aerobic effect. Different strokes work different muscle groups, so incorporating backstroke, butterfly, breaststroke and front crawl means you will cover the range. Even a slow front crawl will burn 300 calories in half an hour.
Find out more: swim4fitness.com; virginactive.co.uk and local authorities. Join a swimming club (britishswimming.org for club details) and you will be able to enter races affiliated by British Swimming.
What it is: Fast-moving dance classes with themes to suit your mood or fitness level. At some of the Virgin Active clubs, for instance, you can try Jazz Aquadance or Island Jam Aqua. "They are a more up-to-date and fun version of aqua-aerobics," says Beale. "They really get you moving in every direction so that all muscles are worked. But the music helps you to forget how tough it is."
Benefits: "When you dance," says Sammy Margo of the Chartered Society of Physiotherapy, "your body is forced to engage the core muscles in the centre of the body around the trunk and lower back." At the same time, a dancer engages the inter-scapular muscles between the shoulder blades so that the middle back opens up and posture is improved, she says. Studies have shown that regular dance can improve mood and researchers reporting in the New England Journal of Medicine recently found that regular dance reduced the risk of dementia in older people.
Find out more: Contact virginactive.co.uk for details of classes at any of its gyms or ask your local authority for information on aqua-dance classes at local pools.