Effect of Functional Impact Training and Yin Yoga on Body Composition and Bone Mineral Density in Breast Cancer Survivors

Breast cancer is one of the most common forms of cancer among women in the United States. Although survival rates have improved following diagnosis, breast cancer survivors (BCS) must contend with the negative effects of the disease and its treatments. Breast cancer treatments can result in accelerated bone and muscle mass loss in conjunction with gains in fat mass. These unfavorable changes lead to reduced strength, physical function, and quality of life (QOL). Resistance training alone as well as a combination of resistance and impact training, such as hopping or jumping movements, have been effective in preventing losses in bone mineral density (BMD) and negative changes in body composition in BCS. More research is needed to determine if there is an alternative exercise mode that can promote improvements in BMD and body composition as well as strength, physical function, and QOL measures. Purpose: The purpose of this study was to examine the effects of 24 weeks of functional impact training (FIT) that combined a circuit of resistance training exercises with high impact exercises compared to a yin yoga program on body composition (lean and fat mass), BMD, blood biomarkers for bone resorption and formation (tartrate-resistant acid phosphatase 5b (TRAP-5b) and bone-specific alkaline phosphatase (BAP)), strength, physical function, fatigue, and QOL in BCS. Methods: Forty-four postmenopausal BCS (60.3 ± 8.3 years) who had completed primary treatment (surgery, chemotherapy, and radiation) were randomly assigned to one of two groups: FIT or yin yoga. Baseline body composition and regional and total BMD were measured via dual energy X-ray absorptiometry (DXA). Blood biomarkers for bone metabolism were analyzed via enzyme-linked immunosorbent assays (ELISA). Upper body strength was assessed using a one-repetition maximum (1RM) chest press, and lower body strength was assessed via isokinetic and isometric knee extension and flexion using the Biodex System 3. The Continuous Scale-Physical Functional Performance (CS-PFP) and a sit-to-stand with the Tendo power analyzer were used to measure physical function. Fatigue and QOL were determined via the Rand 36-Item Health Survey (SF-36), Functional Assessment of Cancer Therapy – Breast Symptom Index (FACT-B), and the Functional Assessment of Chronic Illness Therapy - Fatigue (FACIT-F). Participants completed the 45-minute FIT and yin yoga sessions twice weekly for 24 weeks with 48 hours between the two sessions. Measurements were completed at baseline, after 12 weeks, and at the end of the program. Changes in dependent variables over time were analyzed using repeated measures ANOVA (group by time). An intention-to-treat analysis was used for participants who completed baseline testing, but not the 12- or 24-week assessments. Significance was accepted at p < 0.05. Results: Thirty-two participants completed the study with an adherence rate of 86.6% and 84.4% for the FIT and yin yoga groups, respectively. There were no group by time effects for any measures of BMD. Main time effects were observed for BMD at the left femoral neck (0.883 ± 0.138 g/cm2 to 0.870 ± 0.131 g/cm2) and left forearm measures (total forearm: 0.465 ± 0.078 g/cm2 to 0.457 ± 0.069 g/cm2). There were no other changes in body composition or BMD measures over time. There was a group by time interaction for upper body strength with the FIT group significantly improving in upper body strength (73.2 ± 18.1 kg to 83.2 ± 22.3 kg) compared to the yin yoga group (59.8 ± 14.8 kg to 59.3 ± 15.6 kg). Main time effects were observed for peak isokinetic leg extension and flexion at 60o/sec, 120o/sec and 180o/sec and isometric leg flexion. All participants improved isokinetic leg extension and flexion by an average of 13.2% and 16.2%, respectively. Isometric flexion improved by 7.3%. There were time effects for CS-PFP scores (68.53 ± 12.87 U to 73.66 ± 12.62 U), sit-to-stand peak power (700 ± 202 W to 723 ± 199 W) and peak velocity (0.92 ± 0.22 m/s to 0.95 ± 0.23 m/s), fatigue scores (38.09 ± 11.50 to 42.29 ± 9.88), all domains of the SF-36 except pain, and all domains of the FACT-B and FACIT-F except emotional wellbeing. There were no group by time interactions for any of these measures. Conclusion: Both the FIT and yin yoga interventions improved lower body strength, physical function, fatigue and QOL in BCS. The FIT intervention resulted in improvements in upper body strength compared to yin yoga. Therefore, both programs may be beneficial modes of exercise for BCS looking to improve these outcomes. More research is needed to see if a FIT program of longer duration and higher intensity can elicit improvements in body composition and BMD.