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Wei Liu, Jill Whitall, and Thomas M. Kepple

Functional arm reaching involves multilinked joints: shoulder, elbow, and wrist. We propose that induced position analysis is a useful analytical tool for multijoint coordination of arm reaching. This method was used to compute the contributions of the net joint moment to the hand position when reaching forward. We describe the method and give examples of validating this model with motion capture data. The shoulder and elbow were prime movers of the arm: both acted together with an “overshoot” and “undershoot” pattern respectively to move the hand forward into the final position.

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Xiangyu Liu, Meiyu Zhou, Chenyun Dai, Wei Chen, and Xinming Ye

Surface electromyogram-based finger motion classification has shown its potential for prosthetic control. However, most current finger motion classification models are subject-specific, requiring calibration when applied to new subjects. Generalized subject-nonspecific models are essential for real-world applications. In this study, the authors developed a subject-nonspecific model based on motor unit (MU) voting. A high-density surface electromyogram was first decomposed into individual MUs. The features extracted from each MU were then fed into a random forest classifier to obtain the finger label (primary prediction). The final prediction was selected by voting for all primary predictions provided by the decomposed MUs. Experiments conducted on 14 subjects demonstrated that our method significantly outperformed traditional methods in the context of subject-nonspecific finger motion classification models.

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Hairui Liu, Wei Wang, Chunhe Zhang, and Peter A. Hastie

Purpose: The purpose of this study was to examine the effects of Play Practice (PP) instruction on badminton performance in college students. Method: A total of 66 students from the United States and China participated in units following either the principles of PP or skill-focused instruction. A nonequivalent control/comparison group experimental design with premeasure and postmeasure was used in this study. Separate analyses of variance with repeated measures (Time × Group) were conducted to examine the effects of PP and skill-focused instruction for each of the four dependent variables: (a) forehand clear, (b) wall volley, (c) game performance, and (d) tactical understanding. Results: Both PP and skill-focused instruction conditions were effective in improving participants’ skills from pretest to posttest. However, PP was also effective in improving participants’ game performance. Conclusion: PP effectively developed both fundamental skills and tactical aspects of badminton without diminishing the transfer effect from practice to games.

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Cui Zhang, Qipeng Song, Wei Sun, and Yu Liu

Daily stair activities have become increasingly challenging for older adults with deterioration in physical and cognitive capabilities. However, the dynamic stability of older adults during stair descent under a concurrent dual-task condition remains undetermined. The gait and dynamic stability variables of 40 healthy older adults were measured under single- and dual-task conditions during stair descent. The step length, step width, and single support time did not significantly increase (p > .05) under the dual-task condition during stair descent. The medial–lateral center of mass velocity significantly increased (p < .003), whereas the medial–lateral margin of dynamic stability value significantly decreased (p < .006) at the landing and initial single support under the dual-task condition during stair descent. The self-regulatory ability of healthy older adults under the dual-task condition during stair descent was underestimated. Dual tasking displayed a positive impact on the anterior–posterior dynamic stability of healthy older adults.

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Peter A. Hastie, Wei Wang, Hairui Liu, and Yaohui He

Purpose: The purpose of this study was to examine the effects of Play Practice instruction on the badminton content knowledge and skill of a cohort of Chinese physical education majors. Method: Seventy-two second-year students participated in semester-long courses following either the principles of Play Practice or skill-focused instruction. A control/comparison group experimental design with pre- and postmeasures was used in this study. Separate analyses of variance with repeated measures (Time × Group) were conducted to examine the effects of Play Practice and skill-focused instruction for each of four dependent variables: (a) forehand clear, (b) tactical understanding, (c) game performance, and (d) specialized content knowledge. Results: Students from both conditions made significant improvements in all four variables across the semester. However, students in the Play Practice condition showed significantly greater gains in tactical understanding, game performance, and specialized content knowledge. In particular, while 75% of students who experienced Play Practice reached the 3.0 benchmark score for adequate specialized content knowledge, only 8% of students in skill-focused instruction reached this standard.

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Bo Wang, Zheng Li, Maohua Miao, Xiaoqin Liu, Huiqing Wang, Guoqing Liang, Zhiyong Liu, Yinghao Sun, and Wei Yuan


Research on the relationship between physical activity and aging symptoms among men is limited in China.


Eight hundred nineteen participants aged 40 to 70 (mean age = 58.25) were administered the International Physical Activity Questionnaire and Aging Males’ Symptoms scale (AMS) in face-to-face interviews between 2009 and 2010. Ordinal logistic regression and generalized linear models were used to examine severity of aging symptoms. AMS total score and subscale scores (psychological, somatic, and sexual health) were examined according to physical activity level.


Participants who reported higher levels of physical activity were significantly less likely to develop aging symptoms compared with those who reported lower levels of physical activity, both with (odds ratio [OR] = 0.78, 95% confidence interval [CI]: 0.64 to 0.95) and without (OR = 0.70, 95% CI: 0.56 to 0.87) adjustment for age, body mass index (BMI), smoking, alcohol consumption, and chronic disease. In addition, physical activity was negatively correlated with AMS total score (P < .01) and scores for somatic (P < .01) and sexual (P = .04) health. After covariate adjustment, the negative correlation between physical activity and all AMS scores remained significant (P < .01).


Physical activity is negatively correlated with aging symptoms among middle-aged men in Shanghai.

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Ya-Chen Liu, Wen-Wen Yang, I-Yao Fang, Hope Li-Ling Pan, Wei-Han Chen, and Chiang Liu

Outdoor fitness equipment (OFE) is installed in parks to promote health, particularly among seniors. However, no quantitative study has investigated its effectiveness. Therefore, this study aimed to examine the effectiveness of 12 weeks of OFE training on functional fitness in seniors. Forty-two active seniors were recruited and randomly assigned into OFE and control groups. The OFE group underwent 12 weeks of training using popular OFE for cardiorespiratory function, flexibility, and strength, whereas participants in the control group were asked to maintain their previous lifestyles. The senior fitness test was assessed before and after the 12-week period. Unexpectedly, the results showed no significant improvement within or between the groups after the 12-week training in all parameters (p > .05). In conclusion, the 12-week OFE training failed to enhance functional fitness among active seniors. Potential reasons for the limited training effects might be lack of resistance components and diversity of the OFE design and installation.

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Lu-Wen Chen, Liu-Ing Bih, Chi-Chung Ho, Mao-Hsuing Huang, Chin-Tien Chen, and Ta-Sen Wei


To establish isometric endurance times for trunk-stabilization exercises in 6 different positions and compare 3 kinds of trunk-flexor exercises.


28 healthy young women with no history of disabling back pain.


Isometric endurance times were measured in 6 tests: 60° flexor, 45° flexor, curl-up, extensor, and left- and right-side-bridge exercises.


The mean endurance time was 375 ± 252 seconds for the 60° flexor test; 101 ± 51 seconds, 45° flexor test; 107 ± 54 seconds, curl-up test; 158 ± 45 seconds, extensor test; 70 ± 23 seconds, left-side-bridge test; and 68 ± 23 seconds, right-side-bridge test.


Of the 3 flexor exercises, the 60° exercise was time consuming and had a larger variance. The 45° flexor exercise and curl-up exercise were time effective and showed less variance. The curl-up exercise is easy, convenient, and representative of trunk-flexor effort and can be considered a preferable alternative to the 60° flexor exercise.