Pool-Bound Plyometrics Help You Get Stronger With Less Pain

But do so cautiously.

During plyometric exercise, a muscle lengthens while it is contracting and producing force. This type of exercise program – a mainstay of many athletic team weight-training programs during the off-season – can increase muscle strength in less time than traditional resistance training.

Yet plyometrics can also cause severe muscle soreness and even damage, said Steven Devor, a study co-author and an assistant professor of sport and exercise sciences at Ohio State University. Devor and his colleagues found that doing plyometric exercise in a swimming pool significantly decreased the level of muscle soreness athletes felt two to three days after a workout.

"The participants who did the exercises in water had the same gains in muscle strength as the group that did the workout in a gym," Devor said. "Until now, no one had looked at the possibility of doing plyometrics in water."

The study appears in a recent issue of the Journal of Strength and Conditioning Research.

The researchers asked 32 physically active college-aged women to participate in an eight-week plyometric training program. Each woman had exercised regularly for at least six months and had also participated in organized sports for at least five years. The women agreed to forgo other forms of lower body resistance training and all aerobic workouts during the study.

Half of the women worked out in a gym while the other half exercised in about four feet of water in a swimming pool. Participants repeated several sets of drills of bounding, hopping and jumping on and off of a box. Such exercise helps develop explosive power in major leg and knee muscles and also enhances force production.

Researchers assessed gains in muscle strength and speed at the beginning, middle and end of the study. Assessments included the vertical jump test – the difference between how high a standing person can reach and how high she can reach at the top of her jump; a resistance test that measured the amount of power produced by leg muscles as they pushed against a heavy weight; and a set of timed 40-meter sprints.

Exercise sets and repetitions were increased three times during the study. Muscle soreness and pain sensitivity were tested at those points. Each woman was asked to use a numeric scale that ranged from one to 10 to indicate how sore her legs felt immediately after working out, and also two to three days after the workout. Muscle soreness usually reaches its peak two to three days after working out.

The researchers also used a pressure gauge called an algometer to assess pain sensitivity in the hamstrings, quadriceps and calf muscles. The amount of pressure comfortably applied by an algometer corresponds to how sensitive a person is to pain in that muscle – the more pressure a person can handle, the less sensitive she is to pain.

Both groups reported similar levels of muscle soreness immediately after each workout, but the gym-based group reported significantly more soreness compared with the pool group in their hamstrings, quadriceps and calf muscles two to three days after exercising. Algometer readings showed that women in the gym-based group were also more sensitive to pain.

Muscle strength and mass increased in both groups, as both groups showed the same level of improvement in the three performance measures.

"An appropriately designed aquatic plyometric training program is effective in enhancing power, force and velocity in physically active women," Devor said, adding that men could expect similar effects.

"Impact is not a factor when exercising in water. The strain placed upon working muscles, bones and connective tissue in water doesn't typically lead to injury," he continued.

Skeletal muscle fibers become longer and produce more force during plyometric training. Therein lies the cause of possible muscle damage.

"Most training injuries, such as straining the connective tissue that holds the kneecap in place, inflammation of the Achilles' tendon and heel bruises are attributed to the repetitive and ballistic movements of plyometrics," Devor said.

"But plyometrics build more powerful muscles, since muscles are trained under forces greater than those achieved by conventional slow-speed resistance training."

That additional force observed during plyometric training – and the associated risk for injury – is what makes water an attractive option for people interested in adding plyometrics to their exercise routine.

Devor said that starting an aquatic plyometric routine is best for people who already work out regularly.

Devor conducted the study with Janet Buckworth, Mark Merrick and Leah Robinson, all with Ohio State.