As we age, musculoskeletal conditions may arise that inhibit the ability to carry out impact and resistance exercises (Nordström, Nordström & Lorentzon, 2012). In these cases, low impact activities, such as aquatic exercises, are useful.
Due to the fact that bone responds to mechanical stimulation such as muscle contraction or impact (Kohrt, Barry & Schwartz, 2009), loading/muscle contractions should exceed those which occurs in everyday life (Von Stengel et al., 2007).
Those with joint disorders are likely to feel more comfortable in water due to the reduction in gravitational forces (Bates & Hanson, 1998). However, many studies have found that, due to the lack of impact, aquatic exercises are less osteogenic in children (Karlsson, Nordqvist & Karlsson, 2008), young adults (Karlsson, Nordqvist & Karlsson, 2008) and older adults (Guadalupe-Grau et al., 2009). This has led to aquatic exercise plans often being overlooked by healthcare professionals.
One study (Gómez-Bruton et al., 2013) that assessed the bone mass, metabolism and structure of swimmers, found that swimming has no negative effect of bone mass. The study found that whilst the bone mineral desity of swimmers was similar to sedentary controls, the bone turnover increased. This may lead to stronger structure and therefore stronger bones.
The American College of Sports Medicine (Kohrt et al., 2004) has published guidelines on physical activity and bone health. They recommend that weight-bearing and resistance exercises should be included in activities aimed at preserving bone mass. Proprioception exercises should also be included to improve balance and reduce falls. The proprioception engagement during aquatic exercises will improve balance and muscle strength (Moreira et al., 2013).
The increase in propriception gain from vertical aquatic exercises has shown to have a beneficial effect on physical function (Ruoti, Toup & Berger, 1994). One study (Moreira et al., 2013) compared a high intensity aquatic exercise group to a sedentary control group over 24 weeks. Both groups recieved elementary calcium (500mg/day) and cholecalciferol (100 IU/day). After 24 weeks the number of falls in the aquatic group decreased from 2.00 to 0.29 (P > 0.0001) and the number of fallers decreased by 44% (P > 0.0001). Also, flexibility, unipedal stance, mobility, handgrip strength, back extensor muscle strength, hip flexor muscle strength and knee extensor strength all improved significantly. This study also evaluated the 24 week high intensity aquatic exercise program on bone remodelling markers and bone mass in postmenopausal women. The results showed that bone formation markers (P1NP) had increased (in the exercise group) whilst femoral trochanter bone mineral density had been maintained (against the control groups decrease) (Moreira et al., 2013).This shows that an aquatic exercise program is able to enhance bone formation.
This research shows that bone metabolism can be stimulated by exercising against water resistance. This is increased when exercising at a higher speed, wide range of motion, high intensity and few repetitions. Along with this, the studies showed that aquatic exercises are proficient in icreasing body balance and therefore reducing falls.
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Von Stengel S, Kemmler W, Kalender WA, Engelke K, Lauber D. Differential effects of strength versus power training on bone mineral density in postmenopausal women: a 2-year longitudinal study. Br J Sports Med. 2007;41(10):649-55.
Bates A, Hanson N. Exercícios aquáticos terapêuticos. São Paulo: Ed. Manole, 1998.
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