A Comparison of Concentric and Eccentric Resistance Training on Muscle Hypertrophy

This study was undertaken to determine whether concentric or eccentric muscle action was more likely to induce muscle hypertrophy when exposed to a prolonged heavy resistance exercise program. Fifteen males and 14 females who were not currently or recently involved in a heavy resistance training program for the lower extremities were selected for the study. One group (n = 10) exercised in a concentric fashion, another group (n = 9) exercised in an eccentric fashion, and a third group (n = 10) served as a control group, performing no resistive exercise. The exercising subjects performed three sets of 10 repetitions of resistive knee flexion and extension exercise at 60 degrees/sec, three times per week for 15 weeks at 80% to 100% of their maximal concentric work output on an isokinetic exercise device. Subjects were allowed to increase their intensity of effort as the program progressed to provide continual overload to the exercising muscles to encourage maximal hypertrophy. Isokinetic testing was performed with all subjects at the beginning and at the end of the study, with additional testing of the exercise groups every four weeks to aid in determining effort goals for exercise. Muscle cross-sectional area of the midthigh was measured at the beginning and at the conclusion of the study by computed tomography. Analysis of percentage of increase in muscle cross-sectional area showed that the mean increase in the eccentric, concentric, and control groups was 5.0%, 4.6%, and -1.8%, respectively. A significant statistical difference in hypertrophic response was demonstrated by the exercise groups in comparison to the control group; however, no significant difference in hypertrophy was exhibited in the comparison of the concentric and eccentric groups\u27 results. These results suggest that neither concentric nor eccentric heavy resistance exercise is more likely to promote hypertrophy than the other. However, the results do support the theory that suggests heavy resistance training is more likely to produce increased muscle mass than activity lacking such resistance

A 15-year regional emergency department study of youth sport and recreational injuries

Purpose The aim of this study was to determine frequency and distribution of sports- and recreation-related injuries (SRIs) affecting children and adolescents who visited a northern tier regional medical center emergency department during a 15-year period. Material and methods A descriptive epidemiologic design was employed to retrospectively examine age, gender, month and year of injury, location of injury, sport/recreational activity, mechanism of injury, type and severity of injury, hospital admission and length of stay. Frequency of reported injuries were compared in categories of single factors using Chi-square tests of homogeneity. The impact of risk factors – gender, age class, and sport/activity – on incidence ratios were analyzed via Poisson regression. All statistical analyses were run in R. Results Findings heretofore unreported or inconsistent with previous emergency department (ED) studies include a peak injury occurrence of SRIs during September; a preponderance of head/neck injuries and fractures and a higher percent of admitted patients; frequent occurrence of ice hockey injuries; increased severity of injury during ages 10-14; and a trend during 2000-2014 showing increased injury rate of various types of recreational injuries. Findings consistent with previous ED studies included variable distribution of injuries by age, gender and sport/activity; increased frequency of SRIs during ages 12-15 years and during the warmer months of the year; and trends of increased frequency of SRIs affecting females, increased injury rate of closed head injuries, and decreased occurrence of bicycle injuries during the study period. Further to these findings, several suggestions are made to inform and guide local injury prevention efforts and further research. Conclusions Our study results provide information on a region-specific occurrence and distribution of SRIs in a northern tier hospital catchment area that can be valuable to guide regional injury prevention efforts and further research to evaluate specific patterns identified and success of prevention efforts