December 2022 / January 2023 / February 2023 | Akwa | 41 positively stimulate bone growth. Additionally, there are specific myokines that can negatively affect bone growth dependent on the amount secreted and an individual’s cur- rent homeostasis.3.8-9 Bone likewise functions as a secretory organ, producing and storing osteokines that provide growth factors that positively affect muscle growth and influence other organ.3 Osteo- calcin, produced only in bone and released during exer- cise, positively affects muscle mass in response to exercise. Additionally, there can be negative effects to muscle mass provided by osteokines that are dependent on the amount released or as a function of age.3 Exercise Intensity to Stimulate Bone Growth – Can Water Exercise Provide Sufficient Resistance? There is solid evidence to support the positive effects of exer- cise on bone mass for younger subjects, but studies involv- ing older subjects remains less compelling. Current research indicates that bone strength induced by exercise in the older adult is due to a decreased loss of endocortical bone rather than an increase in bone size seen in young subjects.10 Additionally, optimal interventions favor mechanical stimuli from both gravitational loading and stress exerted by mus- cle and include (1) weight-bearing aerobic exercise such as impact activities or (2) resistance exercises. The aerobic component appears to be most effective in enzyme activation of bone-forming cells (osteoblasts) and cannot be overstated.10 Additionally, there are discrepan- cies in the literature regarding frequency, with three times per week eliciting both muscle strength and femur/hip BMD improvements.4,10 High-volume, resistance training is advo- cated as the critical component of strength-building, while resistance plus impact loading is considered superior for BMD improvement.4,10-11 Because the weight-bearing component may affect vol- ume, it has been suggested that performing a combination of weight-bearing/impact loading plus resistance training on alternate days will maximize the bone-muscle benefits. With respect to volume, consider that the mechano-sensitivity of bone declines soon after a stimulus is applied, so additional volume is of negligible osteogenic value.4 Lastly, all studies that included statistical improvement in BMD, were of long duration (>24 wks.).10-14 The Value of Aquatic Exercise to the Osteoporotic Client The paucity of literature validating positive bone growth with aquatic interventions is partially due to the lukewarm appre- ciation of water exercise for the osteoporotic client. However, to grasp water’s potential, one must first recognize the unique capabilities that water’s physical properties bring to the table. In a population at high risk for fracture, water’s viscosity sup- ports upright posture, exponentially decreasing the fall risk when attempting balance or strengthening activities.15-16 Strength gains equating to functional upgrades and coupled with positive effects on BMD were noted in studies by Fer- nandes Moreira and Keiffer respectively, with the utilization of high-intensity aquatic exercise.16-17 Keiffer noted that “….the improvement in bone metabolism and bone mass observed in our study was not a result of impact exercises in the pool, but a consequence of resistive muscle train- ing against water resistance”17 thus substantiating muscles’ impact on bone formation. In a 2017 systematic review by Simas et al., significant improvement in BMD was noted for both the lumbar spine and femoral neck, although the meta-analysis revealed greater positive statistical changes for both areas using land- based exercise protocols.12 A high-intensity aquatic exercise program for postmenopausal women demonstrated statis- tically significant improvements in both lumbar spine and femur BMD as well as statistically improved scores for func- tional tests post a 24-week aquatics program.13 Lastly, regarding posture (physical characteristics directly impacted by osteoporosis and place individuals at increased fracture risk), a study by Chaves Aveiro et al. demonstrated significant improvement in postural control for osteoporotic postmenopausal women participants. The authors noted that aquatics intervention was more effective than land-based exercise at improving single-leg stance, further underscor- ing the comprehensive benefits afforded osteoporosis clients participating in aquatics.14 In Summary Given the validated benefits aquatic exercise can pro- vide clients with low bone density, it is arguably a safer alternative to land exercise and more appropriate when weight-bearing activity is not tolerable. Aquatic exercise can focus on deficits commonly noted in the osteoporotic population thus improving function, decreasing the fall risk, and managing aerobic concerns that might be unat- tainable with land-based exercise. Appropriate utilization of the unique properties of water has been shown to elicit positive effects on bone. Water has been shown to positively impact balance, strength training, and functional upgrades, and when used appropriately, can provide significant positive bone adaptations. n Resources For a complete list of article references, please email julie@ aeawave.org Author Marty Biondi, PT, DPT, CSCS, FAFS, CEEAA, has been involved in aquatics for over thirty years as a physical therapist and group exercise instructor for various levels. She is part-owner of an outpatient physical therapy clinic where she sees a variety of adult orthopedic and neuro- logic patients. Currently, Marty is involved in research emphasizing functional improvements using aquatic interventions.
