The EMG and load relationship is commonly measured with multiple submaximal isometric contractions. This method is both time consuming and may introduce fatigue. The purpose of this study was to determine if the electromyography (EMG) amplitude from the middle deltoid was reliable during isometric ramp contractions (IRCs) at different angles of elevation and rates of force application. Surface EMG was measured at 3 shoulder elevation angles during IRCs at 4 submaximal levels of maximum voluntary contraction (MVC). Data were reliable in all conditions except during the rate relative to the subjects’ MVC at 90° for 30% and 40% MVC. The main effect for angle on EMG amplitude was found to be significant, p < .01. EMG at 90° was greater than at 60° (p < .017) and at 30° (p < .017). The main effect of force level on EMG amplitude was significant, p < .01 and follow-up contrast demonstrated a significant (p < .001) linear increase of EMG amplitude with force level. We conclude that EMG amplitude from IRCs are reliable across all shoulder elevation angles and up to 40% MVC. IRCs are a feasible method for recording EMG at the deltoid.
David Phillips and Andrew Karduna
Katya Trousset, David Phillips and Andrew Karduna
Proprioception is assessed more often through joint position sense and kinesthesia than force sense. The purpose of this study is to investigate force sense at the shoulder. A total of 12 subjects were recruited. An ipsilateral force reproduction protocol at the shoulder at 50°, 70°, and 90° and 120%, 140%, and 160% baseline torque. Dependent variables were constant error (CE) and root mean square error. An effect was found for load on absolute (p = .001) and normalized CE (p < .001). CE decreased with increased load. An effect for angle was found for absolute root mean square error (p = .002), more accurate at 50° (p = .01), but no effect when normalized (p = .19). With increased loads, subjects undershot the target and CE approached zero. Because of the differing behavior in CE and root mean square error, and absolute and normalized data, force sense studies should examine error from these perspectives.
David Phillips, James C. Hannon and Darla M. Castelli
The effect of an acute bout of physical activity on academic performance in school-based settings is under researched. The purpose of this study was to examine associations between a single, vigorous (70–85%) bout of physical activity completed during physical education on standardized mathematics test performance among 72, eighth grade students at a school in the Southwestern United States. Students received both a physical activity and nonactive condition, in a repeated measures design. Academic performance measures were collected at 30 and 45-minutes post condition. It was hypothesized that students would have greater gains in mathematics test scores post physical activity condition compared with post nonactive condition. Results reported students achieved 11–22% higher math scores at 30 minutes post physical activity condition compared with other time points (45 minutes post PA, 30 and 45 minutes post sedentary) (F(1, 68) = 14.42, p < .001, d = .90). Findings suggest that physical activity may facilitate academic performance in math.
Danielle Nesbitt, Sergio L. Molina, Maria Teresa Cattuzzo, Leah E. Robinson, David Phillips and David Stodden
This paper examined relationships between qualitative (developmental sequences) and quantitative (time) performance in rising from a supine position in early childhood. One hundred twenty two children ranging in age from 3 to 5 years were videotaped for five trials of rising from a supine position. Children’s performance on the supine-to-stand (STS) task was quite variable in terms of both qualitative movement patterns and time (mean = 2.37 s, SD = .60). Results: Component sequences were moderately to strongly correlated with each other (r = .387 to .791). Upper-extremity (r = –.383) and axial (r = –.416) component levels also were inversely correlated with STS time. Results indicated a strong coordinative link between the development of trunk control (i.e., axial movement) and upper-extremity movement levels (r = .791), and together they demonstrated the strongest impact on the ability to rise quickly. These data provide important information relating to a child’s motor development that may have clinical relevance for diagnosis. It provides also a greater understanding on how to improve performance on this task. Future research should examine qualitative and quantitative aspects of STS performance to understand its predictive utility as a lifespan assessment of motor competence and its potential importance as a measure to predict healthrelated variables and functional capability across the lifespan.
Thomas M. Doering, Peter R. Reaburn, Stuart M. Phillips and David G. Jenkins
Participation rates of masters athletes in endurance events such as long-distance triathlon and running continue to increase. Given the physical and metabolic demands of endurance training, recovery practices influence the quality of successive training sessions and, consequently, adaptations to training. Research has suggested that, after muscle-damaging endurance exercise, masters athletes experience slower recovery rates in comparison with younger, similarly trained athletes. Given that these discrepancies in recovery rates are not observed after non–muscle-damaging exercise, it is suggested that masters athletes have impairments of the protein remodeling mechanisms within skeletal muscle. The importance of postexercise protein feeding for endurance athletes is increasingly being acknowledged, and its role in creating a positive net muscle protein balance postexercise is well known. The potential benefits of postexercise protein feeding include elevating muscle protein synthesis and satellite cell activity for muscle repair and remodeling, as well as facilitating muscle glycogen resynthesis. Despite extensive investigation into age-related anabolic resistance in sedentary aging populations, little is known about how anabolic resistance affects postexercise muscle protein synthesis and thus muscle remodeling in aging athletes. Despite evidence suggesting that physical training can attenuate but not eliminate age-related anabolic resistance, masters athletes are currently recommended to consume the same postexercise dietary protein dose (approximately 20 g or 0.25 g/kg/meal) as younger athletes. Given the slower recovery rates of masters athletes after muscle-damaging exercise, which may be due to impaired muscle remodeling mechanisms, masters athletes may benefit from higher doses of postexercise dietary protein, with particular attention directed to the leucine content of the postexercise bolus.
Laura B. Russ, Collin A. Webster, Michael W. Beets and David S. Phillips
A “whole-of-school” approach is nationally endorsed to increase youth physical activity (PA). Aligned with this approach, comprehensive school physical activity programs (CSPAP) are recommended. Distinct components of a CSPAP include physical education (PE), PA during the school day (PADS), PA before/after school (PABAS), staff wellness (SW), and family/community engagement (FCE). The effectiveness of interventions incorporating multiple CSPAP components is unclear. A systematic review and meta-analysis were conducted examining the effectiveness of multicomponent interventions on youth total daily PA.
Electronic databases were searched for published studies that (1) occurred in the US; (2) targeted K–12 (5–18 years old); (3) were interventions; (4) reflected ≥ 2 CSPAP components, with at least 1 targeting school-based PA during school hours; and (5) reported outcomes as daily PA improvements. Standardized mean effects (Hedge’s g) from pooled random effects inverse-variance models were estimated.
Across 14 studies, 12 included PE, 5 PADS, 1 PABAS, 2 SW, and 14 FCE. No studies included all 5 CSPAP components. Overall, intervention impact was small (0.11, 95% CI 0.03–0.19).
As designed, there is limited evidence of the effectiveness of multicomponent interventions to increase youth total daily PA. Increased alignment with CSPAP recommendations may improve intervention effectiveness.