アキレス腱の捻れ構造 : 捻れの程度による分類

Scandinavian Journal of Medicine & Science in Sports. 2015, 25(5), e497-e503博士(保健学)新潟医療福祉大

Effects of Reciprocal Ia Inhibition on Contraction Intensity of Co-contraction

Introduction: Excessive co-contraction interferes with smooth joint movement. One mechanism is the failure of reciprocal inhibition against antagonists during joint movement. Reciprocal inhibition has been investigated using joint torque as an index of intensity during co-contraction. However, contraction intensity as an index of co-contraction intensity has not been investigated. In this study, we aimed to evaluate the influence of changes in contraction intensity during co-contraction on reciprocal inhibition.Methods: We established eight stimulus conditions in 20 healthy adult males to investigate the influence of changes in contraction intensity during co-contraction on reciprocal inhibition. These stimulus conditions comprised a conditioning stimulus-test stimulation interval (C–T interval) of -2, 0, 1, 2, 3, 4, or 5 ms plus a test stimulus without a conditioning stimulus (single). Co-contraction of the tibialis anterior and soleus muscles at the same as contraction intensity was examined at rest and at 5, 15, and 30% maximal voluntary contraction (MVC).Results: At 5 and 15% MVC in the co-contraction task, the H-reflex amplitude was significantly decreased compared with single stimulation at a 2-ms C–T interval. At 30% MVC, there was no significant difference compared with single stimulation at a 2-ms C–T interval. At a 5-ms C–T interval, the H-reflex amplitude at 30% MVC was significantly reduced compared with that at rest.Discussion: The findings indicated that during co-contraction, reciprocal Ia inhibition worked at 5 and 15% MVC. Contrary inhibition of reciprocal Ia inhibition did not apparently work at 30% MVC, and presynaptic inhibition (D1 inhibition) might work

Students’ self-directed learning activities during the OSCE preparation period

This study aimed to clarify the self-directed learning activities of students in preparation for the OSCE, while examining the influences of such an examination on all students’ recognition of learning. A questionnaire survey was conducted, involving students who took the OSCE. The questionnaire consisted of 15 questions; the first one regarded <students’ recognition of their own self-directed learning activities>, followed by those regarding cognitive domain, aff ective domain, psychomotor domain, and self-effi cacy. Based on responses to the first question, students who were not sufficiently performing selfdirected learning activities were identifi ed at the beginning, and, focusing on changes in their self-directedness, they were classifi ed into the following 2 groups at the end of the OSCE preparatory period: those who maintained a passive attitude; and those whose selfdirectedness was enhanced. At the beginning of the period, 48.1% of all students recognized that they were not sufficiently performing self-directed learning activities. While self-directedness was subsequently enhanced in the majority of such students, 16.2% （7.8% of all students） maintained a passive attitude until the end. On comparison between the beginning and end of the period, the recognition of learning was signifi cantly enhanced in all questions in all those whose self-directedness increased during the period. In contrast, in those who maintained a passive attitude toward learning, such improvement was observed for 4 questions, excluding the <recognition of self-directed learning activities>. Furthermore, in all students who took the OSCE, a significant enhancement of recognition was observed for all questions regarding the knowledge and skills necessary for clinical training at the end of the period.本研究の目的は、OSCEの実施準備期間に学習活動の主体性が低い学生に着目しその傾向を把握することと、OSCEの実施が受講学生全体の学習自覚にどう影響しているかについて明らかにすることである。対象と方法は、OSCEを受講した77名の学生に対するアンケート調査とした。質問は15項目で、最初に主体的な学習活動の自覚を質問し、以降、「認知領域」「情意領域」「精神運動領域」に関する項目と自己効力感について質問した。また、全対象学生から学習活動の主体性が低い学生に対象を絞り、さらに、終了時まで主体性が低く留まった学生と終了時には主体性が上昇した学生に分け、分析対象とした。開始時に主体性が低いと自覚していた学生は全体の48.1％であり、そのうちの多くは終了時に主体性が上昇したが、16.2％（全体の7.8％）の学生は継続して主体性が低く留まった。それぞれの学生の学習期間の開始時と終了時の比較では、主体性が上昇した学生は全ての項目で有意に自覚の上昇が認められ、主体性が低く留まった学生では「主体的な学習活動の自覚」を除き4 項目で有意に自覚の上昇が認められた。また、OSCE受講全学生における学習期間前後の比較では、臨床実習に必要な知識や技術を反映する項目の全てにおいて有意に自覚の上昇が認められた

Change in muscle thickness under contracting conditions following return to sports after a hamstring muscle strain injury—A pilot study

The purpose of this study was to measure the change in hamstring muscle thickness between contracting and relaxing conditions following a return to sports after a hamstring muscle strain and thereby evaluate muscle function. Six male track and field sprinters participated in this study. All had experienced a prior hamstring strain injury that required a minimum of 2 weeks away from sport participation. Transverse plane scans were performed at the following four points on the affected and unaffected sides under contracting and relaxing conditions: proximal biceps femoris long head, proximal semitendinosus, middle biceps femoris long head, and middle semitendinosus. The results demonstrated an increase in the thickness of the middle biceps femoris long head and middle semitendinosus regions on the unaffected side with contraction, whereas the affected side did not show a significant increase. The proximal semitendinosus muscle thickness was increased with contraction on both the unaffected and the affected sides. By contrast, the proximal biceps femoris muscle thickness did not show a significant increase on both sides. The results of this study show that evaluation of muscle thickness during contraction may be useful for assessing the change in muscle function after a hamstring muscle strain injury

Effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase

Background An excessive daily cumulative hip moment in the frontal plane (determined as the product of hip moment impulse in the frontal plane during the stance phase and mean number of steps per day) is a risk factor for the progression of hip osteoarthritis. Moreover, walking speed and step length decrease, whereas cadence increases in patients with hip osteoarthritis. However, the effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase are not known. Therefore, this study aimed to examine the effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase. Methods We used a public dataset (kinetic and kinematic data) of over-ground walking and selected 31 participants randomly from the full dataset of 57 participants. The selected participants walked at a self-selected speed and repeated the exercise 15 times. We analyzed the data for all 15 trials for each participant. Multiple regression analysis was performed with the hip moment impulse in the frontal plane during the stance phase as the dependent variable and step length and cadence as independent variables. Results The adjusted R2 in this model was 0.71 (p < 0.001). The standardized partial regression coefficients of step length and cadence were 0.63 (t = 5.24; p < 0.001) and −0.60 (t =  − 4.58; p < 0.001), respectively. Conclusions Our results suggest that low cadence, not short step length, increases the hip moment impulse in the frontal plane. Our findings help understand the gait pattern with low hip moment impulse in the frontal plane

Snack and Nutrient Intake Status of Top-Level Female University Athletes: A Cross-Sectional Study

Ensuring proper energy, nutrient intake, and sleep is vital for athlete health and competitiveness. Despite previous studies investigating the nutrient intake among top-level collegiate female athletes in Japan, the status of snack consumption remains unclear. This study addressed this gap by surveying 70 top-level female university athletes. The survey included a self-administered diet history questionnaire, a qualitative food intake frequency survey, and a survey on snack and dietary supplement use. The results revealed a low frequency of snack intake (2.1 ± 2.3 days/week), with 55.7% of athletes reporting snack consumption. The energy intake in the snack-intake group was significantly higher than that in the without-snack-intake group (31.5 ± 10.0 vs. 26.6 ± 9.92 kcal/kg of BM, p = 0.047). Similarly, carbohydrate intake was significantly higher in the snack-intake group than in the without-snack-intake group (4.84 ± 1.71 vs. 3.96 ± 1.65 g/kg of BM/day, p = 0.035). However, neither group reached the recommended value of 5–8 g/kg of BM/day during the medium training period. Overall, this study emphasizes inadequate energy intake even among athletes with a high snack intake frequency, highlighting the necessity to enhance overall food consumption and underscoring the importance of nutritional education for incorporating appropriate complementary meals to improve performance

Relationship between movement time and hip moment impulse in the sagittal plane during sit-to-stand movement: a combined experimental and computer simulation study

Abstract Background The association between repetitive hip moment impulse and the progression of hip osteoarthritis is a recently recognized area of study. A sit-to-stand movement is essential for daily life and requires hip extension moment. Although a change in the sit-to-stand movement time may influence the hip moment impulse in the sagittal plane, this effect has not been examined. The purpose of this study was to clarify the relationship between sit-to-stand movement time and hip moment impulse in the sagittal plane. Methods Twenty subjects performed the sit-to-stand movement at a self-selected natural speed. The hip, knee, and ankle joint angles obtained from experimental trials were used to perform two computer simulations. In the first simulation, the actual sit-to-stand movement time obtained from the experiment was entered. In the second simulation, sit-to-stand movement times ranging from 0.5 to 4.0 s at intervals of 0.25 s were entered. Hip joint moments and hip moment impulses in the sagittal plane during sit-to-stand movements were calculated for both computer simulations. Results and conclusions The reliability of the simulation model was confirmed, as indicated by the similarities in the hip joint moment waveforms (r = 0.99) and the hip moment impulses in the sagittal plane between the first computer simulation and the experiment. In the second computer simulation, the hip moment impulse in the sagittal plane decreased with a decrease in the sit-to-stand movement time, although the peak hip extension moment increased with a decrease in the movement time. These findings clarify the association between the sit-to-stand movement time and hip moment impulse in the sagittal plane and may contribute to the prevention of the progression of hip osteoarthritis

Activation of the Supplementary Motor Areas Enhances Spinal Reciprocal Inhibition in Healthy Individuals

The supplementary motor area (SMA) may modulate spinal reciprocal inhibition (RI) because the descending input from the SMA is coupled to interneurons in the spinal cord via the reticulospinal tract. Our study aimed to verify whether the anodal transcranial direct current stimulation (anodal-tDCS) of the SMA enhances RI. Two tDCS conditions were used: the anodal stimulation (anodal-tDCS) and sham stimulation (sham-tDCS) conditions. To measure RI, there were two conditions: one with the test stimulus (alone) and the other with the conditioning-test stimulation intervals (CTIs), including 2 ms and 20 ms. RI was calculated at multiple time points: before the tDCS intervention (Pre); at 5 (Int 5) and 10 min; and immediately after (Post 0); and at 5, 10 (Post 10), 15, and 20 min after the intervention. In anodal-tDCS, the amplitude values of H-reflex were significantly reduced for a CTI of 2 ms at Int 5 to Post 0, and a CTI of 20 ms at Int 5 to Pot 10 compared with Pre. Stimulation of the SMA with anodal-tDCS for 15 min activated inhibitory interneurons in RIs by descending input from the reticulospinal tract via cortico&ndash;reticulospinal projections. The results showed that 15 min of anodal-tDCS in the SMA enhanced and sustained RI in healthy individuals

Effect of hip joint angle at seat-off on hip joint contact force during sit-to-stand movement: a computer simulation study

Abstract Background Sit-to-stand movements are a necessary part of daily life, and excessive mechanical stress on the articular cartilage has been reported to encourage the progression of osteoarthritis. Although a change in hip joint angle at seat-off may affect hip joint contact force during a sit-to-stand movement, the effect is unclear. This study aimed to examine the effect of the hip joint angle at seat-off on the hip joint contact force during a sit-to-stand movement by using a computer simulation. Methods A musculoskeletal model was created for the computer simulation, and eight muscles were attached to each lower limb. Various sit-to-stand movements were generated using parameters (e.g., seat height and time from seat-off to standing posture) reported by previous studies. The hip joint contact force for each sit-to-stand movement was calculated. Furthermore, the effect of the hip joint angle at seat-off on the hip joint contact force during the sit-to-stand movement was examined. In this study, as the changes to the musculoskeletal model parameters affect the hip joint contact force, a sensitivity analysis was conducted. Results and conclusions The hip joint contact force during the sit-to-stand movement increased approximately linearly as the hip flexion angle at the seat-off increased. Moreover, the normal sit-to-stand movement and the sit-to-stand movement yielding a minimum hip joint contact force were approximately equivalent. The effect of the changes to the musculoskeletal model parameters on the main findings of this study was minimal. Thus, the main findings are robust and may help prevent the progression of hip osteoarthritis by decreasing mechanical stress, which will be explored in future studies

Sex-related differences in coordination and variability among foot joints during running

Abstract Background Women, as compared with men, have a higher proportion of injuries in the ankle/foot region. However, the reason for this sex-related difference in foot injuries remains unclear. Recently, joint coordination and variability of coordination have been suggested to be a critical index for defining both the state of injury and the potential risk of injury. The purpose of this study was to investigate sex-related differences in coordination and variability among the foot joints during running. Methods Twelve healthy men and 12 healthy women ran on a treadmill. A modified vector coding technique was used to identify coordination and variability among foot joints involving the shank, rearfoot, midfoot, and forefoot segments, and categorized into the following four coordination patterns: in-phase with proximal dominancy, in-phase with distal dominancy, anti-phase with proximal dominancy, and anti-phase with distal dominancy. Results There were no differences in all spatiotemporal parameters and in the foot strike angle between men and women. Coordination of variability of the foot joints during running was similar between men and women, but the anti-phase with proximal dominancy in proportion of frontal rearfoot-shank vs. midfoot-rearfoot couple (men; 7.2%, women; 13.9%) and midfoot-rearfoot vs. forefoot-midfoot couple (men; 18.6%, women; 39.8%) in women was significantly increased compared to that in men. Other all coordination of the foot joints during running differed between men and women, and effect sizes of these parameters were all large. Conclusion The results may be useful for understanding the underlying mechanism contributing to differences in injury risk in men and women, and may provide novel data on foot joint coordination and variability that could be used as reference data for both biomechanical and clinical running studies