A Positive Impact Of Eight Months Swimming On Lumbar Vertebrae In Growing Rats

PURPOSE: Literature is contradictory about the impact of swimming on bone health during growth and there is limited data available for the lumbar vertebra region. To determine the effect of eight-months of swimming during growth on lumbar vertebrae bone mass, geometry and microarchitecture of male rats. METHODS: Male Wistar rats (n = 20, three months; 323 ± 20 g) were randomized into a swimming group (SW; n = 10) submitted to a 2 h/day and 5d/week swimming protocol during eight months and a control group (CON; n = 10) housed in cages with access to a running wheel. Body weight, food intake and running distance were recorded throughout the protocol. At sacrifice, gastrocnemius and soleus muscles, and L4 vertebra were collected. Micro-computed tomography was used to assess L4 vertebra mass, geometry, and trabecular microarchitecture. Groups were compared by independent samples t-test. RESULTS: At sacrifice, body weight and pooled muscle mass were inferior in SW compared to CON (477.3 ± 47.7 vs 533.7 ± 48.2 g; p = .020, d = 1.18; 5.98 ± 0.32 vs 6.54 ± 0.47 g; p = .010, d = 1.14, respectively) despite food intake being identical between groups (p = 0.292). At the L4 vertebra, SW group displayed higher trabecular connectivity density (487.73 ± 151.41 mm-3vs 1051.41 ± 370.05 mm-3; p < .001, d = 2.20,) and lower trabecular separation compared to the CON group (80.92 ± 7.24 vs 91.70 ± 5.94 μm; p < .002, d = 1.65). No differences between groups were found in vertebral body anteroposterior length (SW: 2.84 ± 0.21 mm vs CON: 2.93 ± 0.25 mm; p = .418), trabecular volumetric bone mineral density (SW: 454 ± 35 mg/cm3vs CON: 434 ± 31 mg/cm3; p = .230), bone tissue per volume tissue (SW: 67.84 ± 5.69% vs CON: 67.23 ± 2.35%; p = .759), trabecular thickness (SW: 222.13 ± 34.07 μm vs CON: 226.36 ± 14.32 μm; p = .738), and trabecular number (SW: 3.089 ± 0.309 mm-1vs CON: 2.978 ± 0.171 mm-1, p = .339). CONCLUSION: Swimming during growth induced favourable trabecular microarchitecture adaptations at the rats lumbar vertebrae. No detrimental adaptations on lumbar vertebrae geometry or mass were identified. This study was funded by FCT grant PTDC/SAU-DES/4113/2020. The Research Centre in Physical Activity, Health and Leisure (CIAFEL) is funded by FCT grant UID/DTP/00617/2020 and the Laboratory for Integrative and Translational Research in Population Health (ITR) by FCT grant LA/P/0064/2020. LF and AB a