Muscle Fiber Type Composition and Knee Extension Isometric Strength Fatigue Patterns in Power- and Endurance-Trained Males

Abstract

Muscle fiber type composition in the vastus lateralis and knee extension isometric strength fatigue patterns were assessed in eight endurance-trained and eight power-trained males. Two different 25-trial isometric contraction exercise regimens were administered: a 10-second contraction, 5-second intertrial rest condition designed to induce a fast rate of fatigue and a 10-second contraction, 20-second intertrial rest condition designed to induce a slower rate of fatigue. The power group fatigued almost four times faster than the endurance group in the 10:5 exercise condition. In the 10:20 exercise condition, the endurance group showed no fatigue pattern while the power group had a significant strength decrement of 32%. In both exercise conditions, the power group exhibited more complex fatigue patterns in terms of statistically significant trend components. Maximum isometric strength correlated positively with slow twitch (ST) percent number in power (r = .80) and endurance (r = .48) groups, but negatively with linear trend coefficients in endurance (r = -.62) and power (r = -.80) groups. Maximum isometric strength also correlated higher with fatigue curve trend coefficients than did muscle fiber type composition. Thus, a faster rate of fatigue was associated with higher maximum isometric strength and with higher ST percent number and area. Since maximum isometric strength correlated with body weight (r = .86 for groups combined), both maximum isometric strength and muscle mass appear to be more important determinants of knee extension isometric strength fatigue patterns than muscle fiber type composition.     

Factors Related to Rural Young Adolescents' Participation in Outdoor,Noncompetitive Physical Activity

Purpose: Young adolescents who have little interest in participating in competitive team sports are at an increased risk for physical inactivity. Noncompetitive outdoor physical activity can provide young adolescents with increased opportunities to participate in physical activities that appeal to them and have positive health effects. The purpose of this study was to examine factors related to rural young adolescents' participation in noncompetitive outdoor physical activity to inform intervention design. Method: Young adolescents aged 10 to 14 years old (N = 1,032) from 1 rural county completed a self-administered questionnaire assessing constructs from self-determination theory (SDT) and the theory of planned behavior (TPB) related to noncompetitive outdoor physical activity. Structural equation modeling was used to examine an integrated conceptual model of hypothesized relationships among constructs. Results: The hypothesized conceptual model provided a good fit to the data with greater perceptions of autonomy support and self-determined motivation having statistically significant positive indirect effects on participation in noncompetitive outdoor physical activity mediated by the constructs of the TPB. All direct paths in the model were statistically significant; however, the direct effect of attitudes on intention was weak (.08) and self-determined motivation had no indirect effect on intention through attitudes (.03). Conclusions: Constructs of SDT and TPB should be accounted for by interventions targeting noncompetitive outdoor physical activity among young adolescents. More research is needed to determine young adolescents' preferences for noncompetitive and competitive physical activity and the potential influence that noncompetitive outdoor physical activity may have on total daily physical activity.     

Accuracy of sequential sub-field synchronization of multiple digital camcorders through numerical optimization

The use of digital camcorders in biomechanical analyses can introduce errors due to inter-camera time offsets. The faster the motion being recorded the greater the error. A sequential synchronization method was developed in this study to achieve sub-field camera synchronization for multiple camcorders through numerical optimization. A recreational golfer performed ten drives while being recorded with four digital camcorders (60-Hz sampling rate). Video signals were sampled at 10,000 Hz to determine the actual inter-camera time offsets. The optimized inter-camera time offsets were computed based on three markers placed on the shaft, each separated by 200 mm. The inter-camera time offset error was computed as the difference between the optimized and actual inter-camera time offsets. The inter-camera time offset error reduced on average from 0.518 to 0.019 fields (1 field = 16.7 ms) or less due to sequential optimization. The optimized global reconstruction errors were less than 19% of the unadjusted values. It was concluded that the ability to synchronize multiple (two or more) cameras using a sequential sub-field optimization strategy promises to extend the use of relatively inexpensive digital camcorders to motions considered too fast for the low field rates of such cameras. The sequential approach presented provides a balance between computation time and reconstruction accuracy.     

Study abroad as a collaborative endeavor

Gary Rhodes, Albert Biscarra, Lisa Loberg, and Katie Roller suggest that the next steps to improve study‐abroad programs are to increase the diversity of student participants and partner with departments across the academic and student affairs spectrum.     

Laptop initiative: Impact on instructional technology integration and student learning

The purpose of this study was to examine how 1:1 laptop initiative affected student learning at a selected rural Midwestern high school. A total of 105 high school students enrolled in 10th–12th grades during the 2008–2009 school year participated in the study. A survey instrument created by the Mitchell Institute was modified and used to collect data on student perceptions and faculty perceptions of the impact of 1:1 laptop computing on student learning and instructional integration of technology in education. Study findings suggest that integration of 1:1 laptop computing positively impacts student academic engagement and student learning. Therefore, there is need for teachers to implement appropriate computing practices to enhance student learning. Additionally, teachers need to collaborate with their students to learn and understand various instructional technology applications beyond basic Internet browsing and word processing.