"Pools are excellent environments in which to train… water provides buoyancy and resistance properties that allow the individual to undertake exercise with minimum impact on the body."Angela Calder (performance consultant for Australian Institute of Sport)
If the pool is such a great training environment, why does it not feature far more prominently in our athletic clients’ rehabilitation and recovery sessions? Although the extent to which pool training is used will vary from country to country, the unavoidable reality is that most sports support professionals fail to use water workouts as a rehab tool for one simple reason: ignorance.
That was certainly true in my case 10 years ago, when I started working at the Sports Injury and Rehabilitation Centre in Lilleshall, central England. Up until then I’d only ever gone to the pool to swim, play on inflatables and do some top bombing from the diving boards. At Lilleshall I had my first exposure to pool-based training as part of the rehabilitation programme for footballers receiving treatment at the centre. Even then, it didn’t occur to me that you could also use the pool as a training tool when you weren’t injured. It wasn’t until I started working with the England netball team that I was exposed to the use of the pool in this way.
With the help of the team coach and Marques Church, a clever strength and conditioning coach from New Zealand, who shared all his knowledge with me, I soon started to include a wide range of pool-based training in my athletes’ programmes. Ten years on, I have learned a great deal about how water workouts can improve body alignment, aerobic and anaerobic fitness, flexibility, strength and overall balance and coordination, and I still use the pool with my athletes for training, recovery and rehabilitation. Below I set out some of the applications and drills I have found invaluable over the years.
To be able to use the pool effectively, you must first understand a little about the properties of water, the effect of water immersion on physiology and how both of these things affect our movement and function.
Key properties of water
Buoyancy: The term used to describe a fluid force that always acts vertically upwards. It was, of course, the Greek mathematician Archimedes who first worked out the magnitude of a buoyant force in his famous principle: the buoyant force acting on a body is equal to the weight of the fluid displaced by the body(1,2,3). Buoyancy is helpful in training because it enables the water to support the body, which is particularly useful during rehabilitation from injury. You can also increase an athlete’s buoyancy with the aid of floatation devices such as belts and vests.
Hydrostatic pressure: In a fluid, this increases with depth, and is applied over the surface of any object immersed in the fluid(1,2). This turns out to be another valuable property in rehabilitation: the increased pressure on the body can be used to reduce swelling and allow the athlete to exercise an injured limb without the risk of aggravating swelling.
Fluid dynamics (flow): When an object such as a human hand moves slowly through water, there is little apparent disturbance around the hand. As the speed of movement increases, waves and eddies are created(1,2). Two different types of flow exist: l laminar, characterised by smooth layers of fluid molecules flowing parallel to one another l turbulent, characterised by a mixing of the layers of fluid molecules.
In pool training, we can alter the fluid dynamics to change the intensity of the training session. If the athlete maintains a streamlined shape, they will produce minimal disruption to flow. But when they adopt an unstreamlined shape or use an unstreamlined object such as a float, they will disturb flow and increase drag, which ups the intensity of the movement.
Depth: There is an inverse relationship between water depth and the amount of body weight supported by the musculoskeletal system. When you stand on the bottom of the pool immersed up to your neck, your body is bearing about 8% of its weight. Drop the water level to around mid chest and the body bears 28% to 35% of its weight, increasing to 47% to 54% at waist height (see Table 1, below)(4). So by changing the level of the body in the water you can increase or decrease loading on the musculoskeletal system, which is very useful for rehab and injury prevention. Bear in mind, though, that the values in Table 1 reflect static weight bearing: if your athlete is bouncing up and down, lifting arms above their head etc, the loading values will increase proportionate to the amount of the body out of the water.
How the body behaves in water A body in water produces a different physiological response to how it behaves on dry land, so it is essential that the therapist or coach understands the key differences. Cardiovascular system Respiratory function decreases, because of increased pressure on the thoracic cavity. We lose up to 9% of our vital capacity (total volume of air forcefully expired after maximal inspiration)(5). The rate at which we breathe increases, but sub-maximal and maximal heart rates tend to be 8% to 10% lower (10-20bpm) than on dry land(6). Maximal oxygen uptake values (VO2max) can decrease by around 17% (5,7,8) – although this does not affect your ability to use water-based training to improve your athletes’ VO2max (see below). Note, however, the importance of the correct water temperature: warm water can increase cardiovascular demand over and above the demands of exercise. One study(9) found that cardiac output increased significantly at 40C compared to 25C or 34C. The study also noted that at 36C the centralisation of peripheral blood flow was overcome by the thermal stimulus to increase heart rate. The message here is that you do not want to put an athlete into a pool for an intense training session if the temperature is greater than 28C because of the increased risk of thermal stress. The changes to cardiovascular response require the coach to do some maths and recalibrate the appropriate values for their athletes to achieve when they work in water. I learned from experience that it is not a good idea to try to get an athlete’s heart rate up to levels comparable with those you would expect them to achieve during an aerobic workout on dry land. It’s not that they are just being lazy! There are equations that can supposedly predict maximum heart rates for water-based drills, but I prefer to get the athlete to use a heart rate monitor and gauge their HR response against the usual tests (observation, RPE etc) or against values recorded in a water-based maximal training session that you have previously conducted. Either method should allow the coach to set training zones equivalent to those used on dry land. Although I have found no research on anaerobic work in the pool, I do use it for anaerobic conditioning sessions. I apply the same training principles as on dry land (adapted as appropriate for water work), namely:- high-intensity efforts with recovery efforts in between ; - 20 to 30min session duration
I favour the flexed running position (see below) because it allows the athlete to switch into a higher cadence and thereby kick into the high-intensity work phase in the least amount of time.
Muscular system The muscle actions that we so carefully deconstruct and use as the basis of our strength and conditioning programmes with athletes on dry land change dramatically in water, as this is a virtually gravity-free environment. The key conceptual difference is that the normal prime-mover deceleration action (eccentric contraction or lengthening against resistance) does not always apply in the water. Depending on the movement and the training equipment being used, some muscle actions below the water surface are concentric only. This in turn means that the ‘antagonist’ muscle takes on the prime mover role for the ‘eccentric’ or return phase of an action, but moving concentrically. Using a bicep curl as an example, on land with weights (dumbbells), gravity acts on the weight and the biceps work eccentrically (lowering phase) and concentrically (lifting phase) during the curl. If you perform the same exercise in the water just wearing webbed gloves, force is generated against the direction of your motion, so the biceps contract concentrically in one direction (up or flexing) and the triceps contract concentrically in the other (down or extending). If you now perform the same exercise without the webbed gloves but using dumbbells made from foam to provide buoyancy, you have to work against the effects of buoyancy and the triceps will be working eccentrically and concentrically during the bicep curl. This all gets very complicated, particularly if you are undertaking strength work in shallow water (where there is some gravitational effect on the body). There is very scant research work on this area to help us, either. The best we can say here is that, as the example of the bicep curl shows, therapists should not assume that a specific muscle strengthening exercise on dry land can be reproduced in the water in order to achieve the same rehab goal.
Nervous system Research shows we have a higher pain threshold when immersed in water, and patients with lower-limb arthritis show significant improvements in proprioception and balance with water-based training(10). It is reasonable to suggest that athletes recovering from joint injuries such as ACL rupture might enjoy similar improvements in proprioception in the water.
Is swimming a good workout? Swimming is undoubtedly a great way of training the cardiovascular and musculoskeletal systems, but I will always prefer aqua training over a swim session for my clients, for two main reasons. First, most land-based athletes are not trained swimmers. If you are a strong swimmer with great technique, then swimming may be a good cross-training modality, but I have found that I can train my athletes quickly and effectively in the aqua running techniques described below to a level that produces a really valuable training effect. I know that it would take far longer to get them to a good enough standard of swimming to obtain similar results, and time is a precious commodity in sports rehab and conditioning. Second, most of my clients are involved in running-based activities, so swimming offers less transferable benefits than drills that replicate the movement patterns of their land-based activities.
How to plan effective workouts - Cardiovascular training
Deep water running is a good alternative to pounding the streets day after day(5,6). In a joint study, researchers from England and Tasmania compared the effectiveness of deep water running and road running in improving maximum oxygen uptake in a group of 20 untrained young women. Both training programmes produced similar and substantial improvements in VO2max, and the researchers concluded that deep water running, in common with other aerobic activities, offers significant cardiovascular benefits when performed at an appropriate frequency (three to five days a week), intensity (60% to 75% of maximum heart rate) and duration (20 to 60 minutes)(11).
Aqua jogging/running The two terms tend to be used interchangeably. Although I believe the two adapted techniques outlined below give more bangs for your buck, ‘standard’ aqua jogging is a good training technique, so here are the basic rules on form: l Maintain almost upright body position, with just a slight forward lean from the pelvis (5 to 10 degrees) l Keep trunk ‘tight’ l Bring the knees to approximately 90 degrees and simply push the foot straight down behind you (avoid a bicycling movement) l Pull the arms forward and back with no lateral movement, keeping the hands relaxed and relaxed thumbs pointing up (see Figure 1, over).
I frequently hear coaches and athletes argue that standard aqua jogging is too easy to provide an adequate workout. It is true that this kind of running in deep water doesn’t really create a lot of disruption to the flow. So I adapt it, using techniques shown to me by Marques Church, to increase the level of challenge for the athletes I work with, and they happily accept that these sessions are as tough as anything they undertake on dry land. It is well worthwhile trying these out yourself to get a sense of the effort required. You can progress or alter the intensity of these drills by employing any of the following techniques: l using fins on feet l using a 2:1 ratio of feet to hands (two leg drives to each arm drive) or vice versa l attaching floats to arms or legs (watch for excessive build up of lactate) l using bungees attached to the side of the pool to add variety or as a tool for interval work (go to full extension and hold/go to full extension then drift and repeat/go to extension, drift back to edge of pool and go out again).
Drill 1: Flexed position running A whole-body exercise similar to running. Unlike standard aqua jogging, when performing this drill the body will be almost horizontal. This technique is particularly useful for games players (hockey, rugby etc) who adopt a flexed position. You will get increased activation around the gluteals, hip flexors and hamstrings.
Technique l Work in deep water where your feet cannot touch the ground l Once in the water, lower your hips so you maintain a forward lean from the pelvis of about 45 degrees l Keep trunk ‘tight’ l Reach straight forwards to full extension with one arm, then pull your arm back with palm leading. Bend your arm as you pull back, until approx 90 degrees at elbow, then continue pulling through to your hip l Bring opposite knee forward towards your chest (keep toes pulled up so foot is flexed) while pushing the other leg straight back until fully extended. Keep toes/foot flexed until the bottom of the leg drive, when the foot may plantar-flex l Maintain hip, knee and ankle alignment (avoid using a ‘breast-stroke’ leg movement, especially when fatigue starts to set in).
Drill 2: Upright running This form of aqua running (see Figure 2, right) is predominantly used for recovery specific to upright running musculature, cadence development and maximal resistance work. It also helps improve flexibility and range of movement, which has particular benefits for slow runners who shuffle along with a short stride length. We’ve also found that our horizontal jumpers returning from injury like this technique because the large range of movement helps to stop them from ‘tightening up’ during their rehabilitation.
Techniquel Maintain almost upright body position, with just a slight forward lean from the pelvis (5 to 10 degrees) l Keep trunk ‘tight’ l Reach straight forward to full extension with one arm. Pull arm back with palm leading (scoop action), until the elbow bends to approx 90 degrees. Continue to pull through to your hip l Bring opposite knee forward towards your chest (keep foot flexed), extend the leg forwards. Once fully extended in front of the body, pull leg straight back through the water, aiming to keep the leg as straight as possible. Push toes out (plantar-flex) at the bottom of the leg drive l Maintain hip, knee and ankle alignment.
Drill 3: Cross-country ski running In this drill the legs remain straight throughout and the major movement comes from the pelvis, rather than the knee, which creates much greater gluteal contraction. This is a great drill for warming up and provides increased gluteal function and pelvic control. Good for lower limb recovery.
Technique l Maintain almost upright body position, with just a slight forward lean from the pelvis (5 to 10 degrees l Keep trunk ‘tight’ l Adopt an ‘opposition position’, extending your right arm and left leg forward at the same time l Keeping both arms and legs straight, begin to ‘scissor’ walk l You should aim to swing your arms and legs an equal distance in front and behind the line of your body l Keep hands relaxed with relaxed thumbs pointing up. If you want to increase the intensity you can turn your hands to form a paddle, flex each foot as it drives forwards, and point it pushing back.
For anaerobic cardiovascular training, see Table 2 (below), which gives an illustrative session that I run with participants using a flexed running position. Strength and power training Pool-based plyometrics can be excellent for strength and power development. While I’ve had some interesting conversations (arguments) with coaches who don’t believe you can develop power in the pool, my own experience suggests otherwise and there is even some research to back me up. In 2001 researchers found that it was possible to make improvements in vertical jump performance by using a pool-based plyometrics programme and that there were no significant differences between land and water-based training methods(10). More recently, in 2005, US researchers showed that pool-based plyometrics can produce significant increases in vertical jump scores and provide similar benefits to land-based plyometrics (12). This is great news for anyone looking for a low-risk power-based training tool. I’ve also used this very successfully with athletes returning from injury. Research has shown that on dry land the musculoskeletal system is subjected to minimum impact forces of three to five times bodyweight when landing during plyometric drills such as depth jumps. For this reason, most high-intensity land-based plyometric drills are out of bounds for athletes returning to fitness. But plyometric training in water allows them to slot back into the training programme early. A 70kg male performing a plyo drill in a pool will reduce the impact forces from a range of 210kg to 350kg to a range of 35kg to 57kg. Not bad if your knees are a bit on the dodgy side! The Ohio-based team found that many healthcare professionals now use the pool for injury rehab, and several publications expound the virtues of pool-based plyometrics(10). You can change the intensity level simply by changing the level of the water. The water provides support as the athlete’s body moves downwards, and resistance as the athlete explodes upwards. The water will also add resistance to lateral movements, with the potential benefit of improved strength (a massive bonus for athletes attempting to get back to full fitness after an enforced injury layoff). As water-based strength and power training is still very underdeveloped, there seem to be no hard and fast rules. The Ohio University team suggests you adopt the same training principles as on dry land (volume, intensity, frequency). Table 3 is an illustration of sessions I have used with athletes, including netball players with chronic knee injuries preparing for international competition. The players were able to maintain strength and power without the need for land-based plyometric training sessions.