The skeleton shows greatest plasticity to physical activity-related mechanical loads during youth but is more at risk for failure during aging. Do the skeletal benefits of physical activity during youth persist with aging? To address this question, we used a uniquely controlled cross-sectional study design in which we compared the throwing-to-nonthrowing arm differences in humeral diaphysis bone properties in professional baseball players at different stages of their careers (n = 103) with dominant-to-nondominant arm differences in controls (n = 94). Throwing-related physical activity introduced extreme loading to the humeral diaphysis and nearly doubled its strength. Once throwing activities ceased, the cortical bone mass, area, and thickness benefits of physical activity during youth were gradually lost because of greater medullary expansion and cortical trabecularization. However, half of the bone size (total cross-sectional area) and one-third of the bone strength (polar moment of inertia) benefits of throwing-related physical activity during youth were maintained lifelong. In players who continued throwing during aging, some cortical bone mass and more strength benefits of the physical activity during youth were maintained as a result of less medullary expansion and cortical trabecularization. These data indicate that the old adage of "use it or lose it" is not entirely applicable to the skeleton and that physical activity during youth should be encouraged for lifelong bone health, with the focus being optimization of bone size and strength rather than the current paradigm of increasing mass. The data also indicate that physical activity should be encouraged during aging to reduce skeletal structural decay.exercise | intracortical remodeling | osteoporosis | peak bone mass

Objective To evaluate the effect of combining a continuous epitendinous suture with three‐loop pulley (3LP) and locking‐loop (LL) core patterns for flexor tendon repair. Study design Ex vivo biomechanical study. Sample population Seventy‐two cadaveric superficial digital flexor musculotendon (SDFT) units. Methods Tendons were divided into four groups (n = 18/group). After sharp transection, SDFT were repaired with 3LP, LL, 3LP + epitendinous (E), or LL + E suture patterns. After preloading, repaired constructs were tested to failure. Video data acquisition allowed evaluation of failure mode and quantitation of gap formation. Yield, peak, and failure force were measured from force‐displacement data. Significance was set at P < .05. Results Mode of failure did not differ between repairs with or without an epitendinous suture (P = .255). Gap formation was best prevented with 3LP compared with LL when used alone (P = .001). Mean yield force for 3LP, LL, 3LP + E, and LL + E were 91.4 N ± 25.4, 61.3 N ± 18.4, 195.2 N ± 66.0, 165.3 N ± 46.8, respectively. Tenorrhaphies combined with an epitendinous suture achieved higher yield (P < .0001), peak (P < .0001), and failure forces (P < .0001), without gapping between tendon ends. Conclusion Addition of an epitendinous suture eliminated gapping between tendon ends until failure and increased resistance to loads tolerated at the repair site. Clinical significance The addition of an epitendinous suture may increase the strength of tendon repairs and resistance to gap formation over core suture use alone. The influence of epitendinous suture placement on tendinous healing and blood supply warrants in‐vivo testing.

Objective To determine the effects of different epitendinous sutures (ES) in addition to core locking‐loop (LL) sutures on the mechanical properties and gap formation in a canine cadaveric tendon model. Study design Experimental, ex vivo, biomechanical study. Sample population Seventy‐two cadaveric superficial digital flexor tendon specimens. Methods Superficial digital flexor tendon specimens were divided into four groups (n = 18): sharply transected and repaired with LL, LL + simple continuous ES, LL + Silfverskiöld cross‐stitch ES, and LL + interlocking horizontal mattress ES. Constructs were loaded to monotonic failure. Failure modes, gapping, yield, peak, and failure forces were analyzed. Significance was set at P < .05. Results Yield, peak, and failure forces increased by 2.5‐fold, two‐fold, and twofold, respectively when ES groups were compared with core LL suture patterns alone (P < .0001). Resistance to 1‐ and 3‐mm gap formation was greater in ES groups compared with core LL constructs alone (P < .0001). No differences in yield, peak, failure force, or gapping were observed among ES patterns (P > .827). Conclusion Adding an ES reduced gap formation and increased yield, peak, and failure forces of tenorrhaphies. No difference was detected between the epitendinous patterns tested in this study. Clinical significance The addition of an ES seems more relevant than the specific type of pattern to improve the biomechanical properties of flexor tendon repairs. In vivo studies are warranted to determine the biological implications of the patterns tested here.

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Multicomponent exercise programs are recommended to reduce fracture risk; however, their effectiveness in real‐world community settings remain uncertain. This 18‐month randomized controlled trial investigated the effects of a 12‐month, community‐based, supervised multicomponent exercise program followed by a 6‐month “research‐to‐practice” transition on areal bone mineral density (BMD), trabecular bone microarchitecture, functional performance, and falls in older adults at increased fracture risk. One‐hundred and sixty‐two adults aged ≥60 years with osteopenia or at increased falls risk were randomized to the Osteo‐cise: Strong Bones for Life multicomponent exercise program (n = 81) or a control group (n = 81). Exercise consisted of progressive resistance, weight‐bearing impact, and balance training (3‐days/week) performed at community leisure centers. Overall 148 (91%) participants completed the trial, and mean exercise adherence was 59% after 12 months and 45% during the final 6 months. After 12 months, there were significant net beneficial effects of exercise on lumbar spine and femoral neck BMD (1.0% to 1.1%, p < 0.05), muscle strength (10% to 13%, p < 0.05), and physical function (timed stair climb 5%; four‐square step test 6%; sit‐to‐stand 16%, p ranging <0.05 to <0.001), which persisted after the 6‐month transition. There were no significant effects of the 18‐month intervention on distal femur or proximal tibia trabecular bone microarchitecture or falls incidence, but per protocol analysis (≥66% exercise adherence) revealed there was a significant net benefit of exercise (mean [95% confidence interval] 2.8% [0.2, 5,4]) on proximal tibia trabecular bone volume fraction (Osteo‐cise 1.5% [−1.2, 4.2]; controls −1.3% [−2.6, 0.1]) after 18 months due to changes in trabecular number (Osteo‐cise 1.7% [−0.9, 4.3]; controls −1.1% [−2.4, 0.2]) but not trabecular thickness (Osteo‐cise − 0.2% [−0.5, 0.2]; controls −0.2% [−0.4, 0.0]). In conclusion, this study supports the effectiveness of the Osteo‐cise: Strong Bones for Life program as a real‐world, pragmatic, evidence‐based community exercise program to improve multiple musculoskeletal health outcomes in older adults at increased fracture risk. © 2019 American Society for Bone and Mineral Research.