Midhumerus adaptation in fast-pitch softballers and the effect of throwing mechanics.

PURPOSE: Throwing is a vigorous activity that generates large internal loads. There is limited evidence of the effect of these loads on bone adaptation. The aim of this study was to investigate the 1) magnitude of bone adaptation within the midshaft humerus of female fast-pitch softball players and 2) influence of throwing mechanics (windmill vs overhand throwing) on the magnitude of adaptation. METHODS: Midshaft humeral bone mass, structure, and estimated strength were assessed via peripheral quantitative computed tomography in fast-pitch softball players (throwers; n = 15) and matched controls (controls; n = 15). The effect of throwing was examined by comparing dominant-to-nondominant differences in throwers to controls, whereas the influence of mechanics was determined by comparing dominant-to-nondominant differences in throwers who primarily play as pitcher (windmill thrower), catcher (overhand thrower), or fielder (overhand thrower). RESULTS: Throwers had greater dominant-to-nondominant difference in midshaft humeral bone mass, structure, and estimated strength relative to controls (all P < 0.05). The largest effect was for estimated torsional strength with throwers having a mean dominant-to-nondominant difference of 22.5% (range = 6.7%-43.9%) compared with 4.4% (range = -8.3% to 17.5%) in controls (P < 0.001). Throwing mechanics seemed to influence the magnitude of skeletal adaptation, with overhand throwers having more than double dominant-to-nondominant difference in midshaft humeral bone mass, structure, and estimated strength than windmill throwers (all P < 0.05). CONCLUSIONS: Throwing induces substantial skeletal adaptation at the midshaft humerus of the dominant upper extremity. Throwing mechanics seems to influence the magnitude of adaptation, as catchers and fielders (overhand throwers) had twice as much adaptation as pitchers (windmill throwers). The latter finding may have implications for skeletal injury risk at the midshaft humerus in throwing athletes.

Full-text publication of abstract-presented work in physical therapy: do therapists publish what they preach?

BACKGROUND AND OBJECTIVE: Professional meetings, such as the American Physical Therapy Association's (APTA's) Combined Sections Meeting (CSM), provide forums for sharing information relevant to physical therapy. An indicator of whether therapists fully disseminate their work is the number of full-text peer-reviewed publications that result. The purposes of this study were: (1) to determine the full-text publication rate of work presented in abstract form at CSM and (2) to investigate factors influencing this rate. METHODS: A systematic search was undertaken to locate full-text publications of work presented in abstract form within the Orthopaedic and Sports Physical Therapy sections at CSM between 2000 and 2004. Eligible publications were published within 5 years following abstract presentation. The influences of APTA section, year of abstract presentation, institution of origin, study design, sample size, study significance, reporting of a funding source, and presentation type on full-text publication rate were assessed. Characteristics of full-text publications were explored. RESULTS: Work presented in 1 out of 4 abstracts (25.4%) progressed to full-text publication. Odds of full-text publication increased if the abstract originated from a doctorate-granting or "other" institution, reported findings of an experimental study, reported a statistically significant finding, included a larger sample size, disclosed a funding source, or was presented as a platform presentation. More than one third (37.8%) of full-text publications were published in the Journal of Orthopaedic and Sports Physical Therapy or Physical Therapy, and 4 out of 10 full-text publications (39.2%) contained at least one major change from information presented in abstract form. CONCLUSIONS: The full-text publication rate for information presented in abstract form within the Orthopaedic and Sports Physical Therapy sections at CSM is low relative to comparative disciplines. Caution should be exercised when translating information presented at CSM into practice.

Psychotropic drugs have contrasting skeletal effects that are independent of their effects on physical activity levels.

Popular psychotropic drugs, like the antidepressant selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), and the mood stabilizer lithium, may have skeletal effects. In particular, preclinical observations suggest a direct negative effect of SSRIs on the skeleton. A potential caveat in studies of the skeletal effects of psychotropic drugs is the hypoactive (skeletal unloading) phenotype they induce. The aim of this study was to investigate the contribution of physical inactivity to the skeletal effects of psychotropic drugs by studying bone changes in cage control and tail suspended mice treated with either vehicle, SSRI, TCA or lithium. Tail suspension was used to control for drug differences on physical activity levels by normalizing skeletal loading between groups. The psychotropic drugs were found to have contrasting skeletal effects which were independent of drug effects on animal physical activity levels. The latter was evident by an absence of statistical interactions between the activity and drug groups. Pharmacological inhibition of the 5-hydroxytryptamine (5-HT) transporter (5-HTT) using a SSRI reduced in vivo gains in lower extremity BMD, and negatively altered ex vivo measures of femoral and spinal bone density, architecture and mechanical properties. These effects were mediated by a decrease in bone formation without a change in bone resorption suggesting that the SSRI had anti-anabolic skeletal effects. In contrast, glycogen synthase kinase-3[beta] (GSK-3[beta]) inhibition using lithium had anabolic effects improving in vivo gains in BMD via an increase in bone formation, while TCA-mediated inhibition of the norepinephrine transporter had minimal skeletal effect. The observed negative skeletal effect of 5-HTT inhibition, combined with recent findings of direct and indirect effects of 5-HT on bone formation, are of interest given the frequent prescription of SSRIs for the treatment of depression and other affective disorders. Likewise, the anabolic effect of GSK-3[beta] inhibition using lithium reconfirms the importance of Wnt/beta-catenin signaling in the skeleton and it's targeting by recent drug discovery efforts. In conclusion, the current study demonstrates that different psychotropic drugs with differing underlying mechanisms of action have contrasting skeletal effects and that these effects do not result indirectly via the generation of animal physical inactivity.

Throwing induces substantial torsional adaptation within the midshaft humerus of male baseball players.

Athletes participating in unilateral dominant sports are useful models for investigating skeletal responses to mechanical loading as they provide controlled evidence in the absence of completing a randomized controlled trial. Throwing athletes may be an additional model for this purpose as they overload their dominant upper extremity enabling the contralateral side to act as an internal control and load the bones of the upper extremity purely via the generation of internal (i.e. muscular) forces without superposition of externally applied loads (i.e. impact with an external object). The aim of this study was to investigate upper extremity bone adaptation in throwing athletes and explore factors that predict this adaptation. Two cohorts were recruited-male baseball players (throwers; n=15) and matched controls (controls; n=15). Each subject was assessed for shoulder range and strength, and upper extremity bone mass, structure and estimated strength. Throwers had substantially greater skeletal differences between their dominant and nondominant upper extremities than controls, indicating that throwing induces greater adaptation than induced by habitual loading of the dominant upper extremity. Bone adaptation in throwers was localized to the humerus, with the midshaft humerus in the dominant upper extremity of throwers having enhanced bone mass, structure and estimated strength. The largest effect was for estimated strength of the midshaft humerus which had 30% greater polar moment of inertia (I(P)) in throwers and suggests adaptation to resist torsional loads. The skeletal effect of throwing at the midshaft humerus was influenced by playing position with pitchers and catchers displaying greater dominant-to-nondominant differences than fielders, and was predicted by years throwing and dominant-to-nondominant difference in upper arm lean cross-sectional area. The latter two variables explained 67% of the variance in dominant-to-nondominant differences in I(P). Collectively, these data indicate that throwing induces substantial adaptation within the midshaft humerus. Adaptation was primarily in the direction of torsion which is consistent with biomechanical and injury data suggesting throwing introduces high magnitude torsional forces. As the magnitude of adaptation in throwers was equivalent to that observed in athletes participating in other unilateral dominant sports, throwers represent an alternative model for investigating the skeletal effects of mechanical loading.