The effective intensity of exercise load for facilitating recovery from muscle atrophy in mice

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WCPT Congress 2015 / Physiotherapy 2015; Volume 101, Supplement 1 eS633–eS832

(0.41 ± 0.52 N m/kg) at landing phase. Sidestep cutting had peak valgus moment (0.86 ± 0.35 N m/kg). Crossover cutting had peak varus moment (2.68 ± 0.43 N m/kg). Conclusion(s): High knee valgus moment during medial single leg hop at jumping phase, lateral single leg hop at landing phase and sidestep cutting maneuvers may increase ACL load and risk of injury. Medial and lateral single leg hop close to biomechanical property of actual sidestep cutting are more likely valid for predicting the risk of injury. Implications: Evaluations of knee valgus moment during medial, lateral single leg hop may produce effective ACL injury prevention programs in sports involving sidestep cutting. Keywords: Anterior cruciate ligament; Single leg hop; Knee valgus moment Funding acknowledgements: None. Ethics approval: The ethics committee of Japan Institute of Sports Sciences. http://dx.doi.org/10.1016/j.physio.2015.03.3496 Research Report Poster Presentation Number: RR-PO-05-23-Sun Sunday 3 May 2015 12:15 Exhibit halls 401–403 COMPARISON OF FORWARD AND BACKWARD WALKING IN GAIT INITIATION C. Itoh 1 , T. Kasai 1,2 , S. Wakayama 1 1 Hirosaki

University, Graduate school of Health Science, Hirosaki, Japan; 2 Hirosaki Memorial Hospital, Hirosaki, Japan Background: Forward and backward walking is often used for walking balance exercise. However, this analysis focused on steady-state gait, and backward walking research has mostly not been done in gait initiation. For example, gait initiation is frequently impaired in patients with Parkinson’s disease, and this impairment is associated with fall risk. Therefore, identifying differences between forward and backward gait initiation may improve the effectiveness of therapeutic intervention. Purpose: The aim of this study was to compare forward and backward kinematic and kinetic data in gait initiation. Methods: The subjects were normal healthy adult volunteers (5 females, 5 males; mean age (SD) 22 (1.9) years; mean height, 166.7 (10.8) cm; mean weight, 56.9 (8.7) kg. Data collection was carried out in a motion analysis lab with VICON Nexsus and AMTI Force-Plate, and a synchronized self-made signal switch for the start signal. Gait initiation was defined as the interval between the start signal and the footoff for the second leg. First step was swing leg, and second step was stance leg. For statistical analyses, the Wilcoxon test or the paired t-test were performed using R.2.8.1 software.

Results: Selected significant differences were found for each condition, and all significant data showed a large effect size, including fore-aft GRF first peak in the swing leg (p = 0.011, Large ES) and second peak in the stance leg (p = 0.004, Large ES), and vertical second peak (p = 0.039, Large ES) and third peak (p = 0.004, Large ES) in the stance leg. First and second steps were significant (p = 0.00 and 0.01). Forward data were larger than backward data, except for fore-aft GRF. Joint angle data were not compared statistically because of dissimilar gait pattern data. Conclusion(s): GRF and step length were less backward than forward, but backward fore-aft GRF was higher than forward. The joint angle pattern looked like a reversed pattern, but some points indicated a difference pattern. The present results suggest that backward walking generates more foreaft force than forward walking. Implications: Basic research for clinical practice related to pathology of gait. Keywords: Gait initiation; Forward walking; Backward walking Funding acknowledgements: This study was supported by the research budget for a graduate student in Hirosaki University. Ethics approval: Ethical approval was obtained from the Hirosaki University Graduate School of Medicine Ethics committee. http://dx.doi.org/10.1016/j.physio.2015.03.3497 Research Report Poster Presentation Number: RR-PO-04-19-Sat Saturday 2 May 2015 12:15 Exhibit halls 401–403 THE EFFECTIVE INTENSITY OF EXERCISE LOAD FOR FACILITATING RECOVERY FROM MUSCLE ATROPHY IN MICE Y. Itoh 1,2 , N. Agata 2,3 , N. Kimura 4 , M. Inoue-Miyazu 4 , T. Hirano 1 , K. Hayakawa 2 , T. Murakami 5 , K. Kawakami 2 1 Nagoya

Gakuin University, Faculty of Rehabilitation, Seto, Japan; 2 Nagoya University Graduate School of Medicine, Nagoya, Japan; 3 Tokoha University, Faculty of Health and Medical Sciences, Hamamatsu, Japan; 4 Aichi Medical College for Physical and Occupational Therapy, Kiyosu, Japan; 5 Shigakkan University, Faculty of Wellness, Ohbu, Japan Background: Previously, we clarified the facilitating effect of recovery from muscle atrophy by the stand-up exercise load to atrophied mice (WCPT 2011). However, the most effective intensity of exercise for recovery from atrophied muscle has not been elucidated in detail.

WCPT Congress 2015 / Physiotherapy 2015; Volume 101, Supplement 1 eS633–eS832

Purpose: The aim of this study was to clarify the relationship between the intensity of isometric contraction exercises (ICEs) and the facilitating recovery of atrophied muscles. Methods: Mice were performed ICEs at different intensity 50 times per day for 7 days after tail suspension (TS). ICEs were performed by applying electrical stimulation (frequency, 40 Hz; duration, 2.0 ms) to the posterior surface of the mice lower-limbs under anesthesia. To adjust intensity of ICEs, the torque of ankle plantar-flexion during electrical stimulation was set at 1 mN m (ICE1), 3 mN m (ICE3), 5 mN m (ICE5), and 8 mN m (ICE8), by altering electrical current (n = 12, respectively). Effect of ICEs was evaluated using ankle plantar-flexion torque (MCT) measured by applying electrical stimulation (frequency, 100 Hz; current, 5.0 mA) 4 h prior to ICEs. And histological changes of soleus muscles ere evaluated by myofiber cross-sectional area (CSA), number of myonuclei, presence of monocyte-infiltrated myofibers, developmental myosin heavy chain (dMHC)-positive myofibers, Pax7, MyoD, and myogenin-positive cells. One-way analysis of variance and the Bonferroni method were used for comparison between the groups. Significance was set at 5%. Results: Recovery of MCT was facilitated from day 1 after initiating ICE in the ICE3 and ICE5 groups, reaching the same torque as normal muscles on day 4. The myofiber CSA in the ICE3, ICE5, and ICE8 groups were significantly greater than that in the non-ICE group which maintained under normal conditions after TS without performing ICE. However, the myofiber CSA did not recover to normal level in the ICE5 and ICE8 groups. The muscles in these two groups exhibited injured myofibers with monocyte infiltration and dMHC-positive nascent myofibers. Moreover, the increase of the number of myonuclei in the ICE3, ICE5, and ICE8 groups was greater than that of normal levels, but not in the ICE1 or non-ICE groups. Immunochemical staining showed that the Pax7, MyoD, and myogenin are colocalized in mononucleated cells, indicating myogenic satellite cells are activated and differentiated in these three groups. Conclusion(s): The results indicated that the exercise load which is greater than a definite intensity activated myogenic satellite cells and increased the number of myonuclei compared to the normal cage activity or the low intensity exercise. These phenomena were observed in our past study that examined stand-up exercise effects on atrophied muscle, suggesting that the activation of myogenic satellite cell would contributed to the increase of myonuclei number, resulting the rapid recovery of myofiber size in this study. The high intensity exercise such as in the ICE5 and ICE8 groups caused muscle injury, and inhibited recovery of myofiber size. Thus, we conclude that an appropriate intensity of exercise load which not cause injury should be chosen for facilitating recovery from atrophy. Implications: This exercise loading model could contribute to further investigations of mechanisms of recovery from muscle atrophy.

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Keywords: Isometric contraction; Muscle injury; Muscle atrophy Funding acknowledgements: This work was supported by MEXT KAKENHI (Grand-in-Aid for Young Scientific B; 24700566, for Challenging Exploratory Research; 25560274, 26560288). Ethics approval: The experimental protocol was approved by the Ethics Review Committee for Animal Experimentation at our institution. http://dx.doi.org/10.1016/j.physio.2015.03.3498 Research Report Poster Presentation Number: RR-PO-02-01-Sun Sunday 3 May 2015 12:15 Exhibit halls 401–403 RELATIONSHIP BETWEEN MUSCLE STRENGTH, FAT FREE MASS AND EXERCISE CAPACITY IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE K. Iwai 1 , H. Hayashi 2 , Y. Nakano 3 1 Shiga University of Medical Science Hospital, Rehabilitation Units, Otsu, Japan; 2 Shiga University of Medical Science Hospital, Department of Cardiovascular Medicine, Otsu, Japan; 3 Shiga University of Medical Science Hospital, Department of Respiratory Medicine, Otsu, Japan

Background: In general, skeletal muscle mass is reduced in patients with COPD. It is reported that a cross-section area of the skeletal muscle in the lower limbs is associated with the muscle strength. In addition, other factors such as endocrine abnormality and hypoxemia, and malnutrition influence on skeletal muscle mass in patients with COPD. However, it is known that exercise capacity is associated with both skeletal muscle mass and muscle strength in those patients. But, it remains unclear which is more attributed to exercise capacity. Purpose: The aim of this study is to investigate the relationship between fat free mass and muscle strength, and investigate the determinants of exercise capacity in patients with COPD. Methods: The study consisted of 73 patients with COPD (mean age, 74 ± 7.9 years) who during hospitalization, and 37 healthy people without COPD (mean age, 72 ± 6.6 years). All participants were males, and daily activity was independently maintained. Knee extension strength was measured by isometric dynamometer (N m/kg), and fat free mass index (FFMI) was measured by a bioelectrical impedance analysis (kg/m2 ). 6-minute walk test was performed to evaluate to exercise capacity (m). Speaman’s rank test was used to evaluate correlation among variables. Results: Knee extension strength and fat free mass index were not correlation in the two groups. But, exercise capacity