Head impact differences in blind football between Rio 2016 and Tokyo 2020 Paralympic Games: video-based observational study

OBJECTIVE

In Tokyo 2020 Paralympic Games, there were the rule and goal size changes at the blind football competition. This study aimed to compare the scoring and head impact characteristics during blind football competition between the Rio 2016 and Tokyo 2020 Paralympic Games using the official videos.

DESIGN

Video-based observational study.

PARTICIPANTS

In total, 36 blind football (men's football 5-a-side) game videos were obtained from the official International Paralympic Committee.

PRIMARY AND SECONDARY OUTCOME MEASURES

Head impact was defined as the sudden contact of any object with the head. Videos were analysed to assess the number of scores and head impacts along with their corresponding details (ie, round, playing phase, scoring situation, impact situation, occurrence area, impact object, head impact site, fall and foul).

RESULTS

The total number of goals scored at the Tokyo 2020 Paralympic Games was nearly double that at the Rio 2016 Paralympic Games. Regarding head impacts, a total of 2036 cases (Rio 2016, n=1105; Tokyo 2020, n=931) were evaluated. Significant differences were observed in head impact characteristics between the Rio 2016 and Tokyo 2020 Paralympic Games among seven outcomes (round, scoring situation, impact situation, occurrence area, impact object, site of head impact and fall).

CONCLUSIONS

Compared with the Rio 2016 Paralympic Games, the Tokyo 2020 Paralympic Games showed an increase in the number of points scored and different head impact characteristics.

Head Impact in Blind Football During the Tokyo Paralympics: Video-Based Observational Study

ABSTRACT

Head impacts during blind football are common and have high injury rates; however, their characteristics and impact are still underreported. We compared head impact characteristics in blind football players with and without falls on all 18 official blind football match videos from the Tokyo 2020 Paralympic games. The rate of head impacts with falls was significantly higher in the preliminary phase, offense phase, and during dribbling. Significant differences in the region of the head impacted were also observed among the impact subjects/objects. The findings in this study would contribute to the development of injury prevention measures to minimize head injuries from head impact in blind football.

Characteristics of Wheelchair Basketball Falls During the Tokyo 2020 Paralympics by Sex and Physical Impairment Classification: A Video-Based Observational Study

OBJECTIVE

The aim of the study is to evaluate the fall characteristics of wheelchair basketball players by sex and impairment classification using the official videos of the Tokyo 2020 Summer Paralympic Games.

DESIGN

This was a video-based observational study. In total, 42 men's and 31 women's wheelchair basketball game videos were obtained from the official International Paralympic Committee. The videos were analyzed to assess the number of falls, playing time of the fall, playing phase, contact, foul judgment, fall location/direction, and the body part that first impacted the floor.

RESULTS

A total of 1269 falls (men, n = 944; and women, n = 325) occurred. The analysis of men demonstrated significant differences in rounds, playing phase, location of fall, and body part first impacted. Women demonstrated significant differences in all categories except in rounds. Comparisons by functional impairment showed different trends for men and women.

CONCLUSIONS

The detailed observation of videos suggested that men are more likely to have dangerous falls. There is a necessity for discuss the prevention measures based on sex and impairment classification.

The Features of Foot Morphology and Intrinsic Foot Muscle Property in Adolescent Swimmers: An Ultrasound-Based Study

This cross-sectional study aimed to investigate the relationship between foot shape and intrinsic foot muscles (IFMs) in adolescent swimmers compared with other athletes. Foot morphology of swimmers was compared with other athletes of comparable age and a competition level (n = 32 [64 feet]; a total of 64 feet; 128 feet in two groups). Foot morphology and variables of IFMs were measured using a three-dimensional foot scanner and an ultrasound imaging system, respectively. Multiple linear regression analysis with forced entry was performed to clarify the association of the thickness and the cross-sectional area (CSA) of IMFs with the navicular height in both sitting and standing positions. Navicular height in a standing position, the thickness of the abductor hallucis (AbH) and the flexor digitorum brevis (FDB), as well as the CSA were significantly lower in swimmers compared with other athletes (p < 0.05). A larger CSA for the flexor hallucis brevis (FHB) was observed in swimmers than in other athletes (p < 0.01). The navicular height of swimmers in sitting and standing positions was positively correlated with the thickness and the CSA of the FHB and the FDB (p < 0.05). Multiple regression analysis showed that navicular height was associated with the CSA of the FDB in both sitting and standing positions (β = 0.395; p < 0.002, β = 0.201; p < 0.018). This study showed that the navicular height of elite adolescent swimmers was lower than that of other athletes. Furthermore, the swimmers' high navicular height was associated with the CSA of the FDB, suggesting that the FDB might be more involved in the formation of the medial longitudinal arch than the AbH.

Comprehensive inpatient rehabilitation for elite athletes after anterior cruciate ligament reconstruction

[Purpose] The authors' institute offers a comprehensive inpatient approach to rehabilitation after anterior cruciate ligament reconstruction surgery, providing nutritional and psychological support in addition to exercise and physical therapy. This study aimed to determine the outcomes of athletes undergoing this comprehensive rehabilitation program and to compare the outcomes of bone-patellar tendon-bone and semitendinosus/gracilis autograft recipients. [Participants and Methods] Elite athletes who underwent comprehensive inpatient rehabilitation at the authors' institute for at least two weeks after anterior cruciate ligament reconstruction were mailed a questionnaire. Their recovery levels, which were measured against preinjury performance, and secondary anterior cruciate ligament injury rates, were evaluated and compared according to graft type. [Results] Valid responses from 45 athletes were analyzed (bone-patellar tendon-bone [n=12]; semitendinosus/gracilis [n=33]). The frequency of return to preinjury activity levels and secondary anterior cruciate ligament injury were comparable between bone-patellar tendon-bone and semitendinosus/gracilis graft recipients. A greater proportion of athletes returned to preinjury activity levels, while a lower percentage experienced re-rupture compared to previous studies. [Conclusion] A comprehensive rehabilitative approach after anterior cruciate ligament reconstruction may contribute to improved postoperative performance irrespective of graft type. Objective evaluations are needed in the future to clarify the benefits of specific rehabilitative approaches.

Analysis of wheelchair falls in team sports at the Paralympic Games: video-based descriptive comparison between the Rio 2016 and Tokyo 2020 games

OBJECTIVES

To identify the fall characteristics of athletes in wheelchair rugby and wheelchair basketball during the Tokyo 2020 Paralympic Games and descriptively compare these with those of the Rio 2016 Paralympic Games.

DESIGN

Cross-sectional analysis.

PRIMARY AND SECONDARY OUTCOME MEASURES

We obtained video footage from the International Paralympic Committee of the Tokyo 2020 Paralympic Games that included 8 teams from each of the 18 wheelchair rugby and 10 wheelchair basketball games (men and women). The data were analysed to evaluate the number of falls, class difference (low or high pointer), time of play during the fall, phase of play, contact with other athletes, fall direction, fall location and the body part that first contacted the floor during the fall. These data from the Rio 2016 and Tokyo 2020 games were compared.

RESULTS

Overall, 430 falls (rugby, 104; men's basketball, 230 and women's basketball, 96) occurred (average per game ±SD: 5.8±3.1, 23.0±5.4 and 9.6±5.0, respectively). Significant differences in class, direction, fall location and body part point of contact between the three sports were observed. In wheelchair rugby, falls occurred mainly in high pointers and tended to be more lateral due to contact. In wheelchair basketball, falls occurred more in female high-pointers and in male low pointers, with more forward falls due to forward contact. Unlike in the Rio 2016 games, no difference between the events based on the presence or absence of contact was observed in the Tokyo 2020 games.

CONCLUSIONS

The number of falls increased in Tokyo 2020 compared with Rio 2016, with no significant difference in the characteristics of falls between the Rio 2016 and Tokyo 2020 games. Only in men's wheelchair basketball, the number of falls in low pointers significantly increased in the Tokyo 2020 games when compared with that in the Rio 2016 games.

Does the sesamoid rotation angle change differently in subjects with hallux valgus considering foot position during assumed walking? A pilot study

Hallux valgus (HV) entails changes in the alignment of the rotating sesamoids and a shift of the abductor hallucis muscle (ABH) in the plantar direction, decreasing the abductor force. Load on the foot while walking may change the sesamoid rotation angle (SRA). Nevertheless, no study has investigated the relationship between the change in SRA during assumed walking and ABH muscle size. The aim of our study was to examine the changes in SRA at different foot postures assumed to generate skeletal alignments during walking and muscle size of the ABH in participants with HV and to discuss the association between the change in the SRA and cross-sectional area (CSA) of the ABH. Thirteen female participants were recruited and divided into the HV and non-HV groups according to the HV angle. The SRA and cross-sectional area of the ABH were measured using B-mode ultrasound. The SRA was measured under four conditions; sitting, standing, mid-stance, and pre-swing posture. The CSA was assessed in the supine position. In all postures, the SRA increased more in the HV group than in the non-HV group (p < 0.05). The change in the SRA at the pre-swing posture was greater in the HV group than in the non-HV group (p < 0.05). The change in the SRA at pre-swing posture negatively correlated with the CSA of the ABH in the HV group (r = -0.554, p < 0.05). In the HV group, increasing the load on the forefoot enhanced the sesamoid rotation. Abductor torque on the ABH decreased with ABH displacement as the sesamoids moved laterally in the pre-swing. Repeated walking increased sesamoid rotation and led to HV progression. Therefore, it may be beneficial to use an orthosis or arch pad that corrects pronation of the metatarsal with the rotation of the sesamoids.

Biomechanics of Double Poling in Paralympic Cross-Country Skiing—A Cross-Sectional Study Comparing the Standing and Sitting Positions in Healthy Male Subjects

Background and Objectives: Double poling is an important fundamental skill required for cross-country skiing in able-bodied athletes and in those with physical disabilities. Meanwhile, the performance improvement and injury prevention related to double poling requires a thorough assessment, whereas the scapular and shoulder kinematics in different postural conditions remain to be clarified. The main purpose of this study was to evaluate the biomechanics during cross-country ski double poling in the standing and sitting positions. Materials and Methods: Eleven participants underwent kinematic assessments of the shoulder girdle during double poling on a ski ergometer with an electromagnetic tracking device. The cycle rate, stroke length, stroke speed, thorax motion relative to pelvis, scapular motions relative to thorax, humeral motions relative to thorax, and humeral motions relative to scapula were calculated for five double-poling cycles. Results: In the sitting position, the angles of humerothoracic elevation were 18 degrees larger and glenohumeral elevation 13 degrees larger than in the standing position at the upward point and range of motion. Conclusions: The study revealed that double poling in the sitting condition increased the humerothoracic and glenohumeral elevation angle to secure the poling margin. If these are excessive, there is a risk of shoulder injuries such as subacromial impingement.

Shoulder muscle activation during scapular protraction exercise with arm rotation

BACKGROUND

The role of the serratus anterior is to maintain scapular stability. To strengthen this muscle, scapular protraction exercises are typically performed. Although the angle of arm rotation leads to changes in shoulder muscle activation, the arm rotation position is not normally determined.

OBJECTIVE

To investigate if scapular muscle activations were changed by combining arm external rotation during scapular protraction exercises.

METHODS

Thirty-four healthy men were enrolled in this study. Participants were instructed to perform scapular protraction exercises at 90∘ and 120∘ of shoulder flexion while in the standing and supine positions. Two different arm rotation angles were used: the thumb-up position (neutral position) and the maximum arm external rotation (ER) position. The percentages of maximum voluntary contractions (%MVCs) were measured, and %MVCs in the neutral and arm ER positions were compared.

RESULTS

Muscle activities of the middle serratus anterior (MSA) and lower serratus anterior (LSA) in the arm ER position were significantly higher than those in the neutral position during all tasks. The highest MSA and LSA positions were observed with the arm ER position of 120∘ while standing.

CONCLUSIONS

Scapular protraction exercises with arm ER resulted in a higher serratus anterior activity.

Effect of a 4-week static stretching program for plantar flexor muscles on physical performance and muscle properties

BACKGROUND: The effects of a long-term static stretching program on physical performance parameters have not been elucidated completely, although the effects on muscle flexibility have a consensus. OBJECTIVE: This study aimed to investigate the effect of a long-term static stretching program on physical performance and muscle properties. METHODS: Participants performed a 2-min static stretching for the ankle joint 5 times per week for 4 weeks. Physical performance and muscle properties was measured before and after the static stretching program. RESULTS: Results showed that range of motion (ROM), dynamic postural stability, and muscle hardness were positively changed, whereas other variables i.e. maximal isometric plantar flexion moment, jump heights, muscle-tendon junction displacement and its angle, were not. CONCLUSIONS: Four-week of SS program may improve ROM, dynamic postural stability, and muscle hardness without decreasing physical performance.

Tensiomyographic Neuromuscular Response of the Peroneus Longus and Tibialis Anterior with Chronic Ankle Instability

This study aimed to investigate the muscle contractile response of the peroneus longus (PL) and tibialis anterior (TA) in groups with and without chronic ankle instability (CAI) using tensiomyography. Twenty-three adults, 12 with CAI and 11 healthy participants, participated in this study. All subjects underwent a tensiomyographic assessment of the PL and TA to measure delay time, contraction time and maximal displacement. The ankle evertor and invertor normalized peak torques, maximum work done and muscle thickness of the PL and TA were calculated. The delay time and contraction time of the PL in the CAI side were significantly higher than those in the healthy group (p < 0.05); however, no significant difference could be detected in the TA between groups. Furthermore, there was no significant difference in the normalized peak torques, maximum work done and muscle thickness of the PL and TA between groups. The CAI side demonstrated a delayed muscle contractile response of the PL when compared with the healthy group although there was no difference in muscle strength and muscle size. Clinicians should consider the muscle contractile response of the PL for rehabilitation of the ankle evertor with CAI.

Acute effects of local vibration stretching on ankle range of motion, vertical jump performance and dynamic balance after landing

BACKGROUND: Local vibration (LV) used as part of the warm-up can stimulate a specific body part and muscle group, potentially increasing muscle flexibility and performance. However, the effect of its combination with static stretching (SS) has not been thoroughly examined. OBJECTIVE: To elucidate the acute effectiveness of combining LV and SS (V+S) on the ROM of ankle dorsiflexion, squat jump, counter-movement jump (CMJ) and the dynamic postural stability index (DPSI). METHODS: Fifteen healthy men who were regularly involved in recreational sports participated in this study. Static Stretching, V+S, and non-stretching condition (control) were assigned randomly and the intervention period for each condition was five minutes. RESULTS: The dorsiflexion improved significantly in SS and V+S compared to the control. The CMJ height decreased significantly following SS compared to V+S and control. CONCLUSIONS: This study suggests that V+S improves ankle dorsiflexion ROM without compromising jump performance. Local vibration device could be an effective element in warming up but further research is warranted.

The infraspinatus muscle activity during pitching motion in baseball players with shoulder instability

Background

Shoulder microinstability is often overlooked, which can be problematic, especially in overhead athletes. The slipping phenomenon is defined as posterior or lateral sliding of the humeral head in an elevated arm. When the shoulder is close to the end range of stability, the infraspinatus is highly activated and keeps the shoulder in the glenoid cavity. This study aimed to examine the characteristic physical function and infraspinatus activity during the pitching motion in baseball pitchers with shoulder instability.

Methods

Twenty-one male baseball pitchers participated and were divided into 2 groups based on radiograph findings at zero position: slipped (group S) and nonslipped (group N) groups. Physical function using Hara test and infraspinatus muscle activity during pitching were evaluated.

Results

The infraspinatus muscle activity during the acceleration phase was significantly greater in group S (59.5 ± 33.0%MVC) than in group N (33.0 ± 16.9%MVC) (P < .05). Positive rate of the Hara test in group S was significantly high in the loose test and elbow push test.

Conclusions

This study shows that baseball pitchers with slipping phenomenon have capsular laxity and scapular instability that indicate high infraspinatus muscle activity during the acceleration phase. Therefore, repetitive pitching with hyperactivity of the infraspinatus on the slipping shoulder may cause fatigue and dysfunction.

Ultrasonographic Evaluation of the Shoulders and Its Associations with Shoulder Pain, Age, and Swim Training in Masters Swimmers

Background and objectives: The long head of the biceps (LHB) and rotator cuff tendinopathy is the major cause of shoulder pain in competitive swimmers. The risk of tendinopathy increases with aging; however, the structural changes of LHB and rotator cuff in populations of masters swimmers have not been well examined. The purpose of this study was to investigate the prevalence of ultrasonographic abnormalities of the shoulders in masters swimmers, and the association of pain, age, and swim training with structural changes in this population. Materials and Methods: A total of 60 subjects participated in this study, with 20 masters swimmers with shoulder pain, 20 asymptomatic masters swimmers, and 20 sex- and age-matched controls. All swimmers completed a self-reported questionnaire for shoulder pain, their history of competition, and training volume. Each subject underwent ultrasonographic examination of both shoulders for pathologic findings in the LHB tendon, rotator cuff (supraspinatus (SSP) and subscapularis (SSC)) tendons, and subacromial bursa (SAB) of both shoulders and had thickness measured. Results: The prevalence of tendinosis (LHB, 48.8%; SSP, 17.5%; SSC, 15.9%), partial tear (SSP, 35.0%), and calcification (SSC, 10.0%) were higher in swimmers than in controls. LHB and SSP tendinosis were associated with shoulder pain. Older age and later start of competition were associated with an increased risk of LHB tendinosis and SSC calcification. Earlier initiation of swimming and longer history of competition were associated with an increased risk of SSP and SSC tendinosis. The thicker SSP tendon significantly increased the risk of tendinosis and partial tear. Conclusions: A high prevalence of structural changes in the rotator cuff and biceps tendons in masters swimmers reflects the effect of shoulder symptoms, aging, and swim training.

Functional Predictors for Home Discharge after Hip Fracture in Patients Living in Sloped Neighborhoods or Islands: An 8-Year Retrospective Cohort Study

Functional predictors of home discharge after hip fractures have been widely reported; however, no study has considered the geographical features surrounding patients’ homes. This study aimed to identify home discharge predictors and determine the cutoff points required for home discharge of patients living in sloped neighborhoods or islands. A total of 437 postoperative hip fracture patients were included and classified into the flat, slope, and island groups according to their residential area before the fracture. Multivariate logistic regression analysis was used to identify significant home discharge predictors, and receiver-operating characteristic analysis to calculate cutoff values. In all the groups, the functional independence measure-motor score was a significant home discharge predictor, with cutoff values of 69 for the flat group and 65 points for the slope and island group. In the slope group, the 6-minute walking distance (odds ratio, 1.02; 95% confidence interval, 1.01–1.04) and revised Hasegawa dementia scale score (odds ratio, 1.06; 95% confidence interval, 1.01–1.12) were also identified as predictors, with cutoff values of 150 m and 18 points, respectively. The outcomes required for home discharge after hip fracture differ depending on the neighborhood terrain, especially for patients living in areas with many slopes and stairs.

Analysis of team-sport wheelchair falls during the Rio 2016 Summer Paralympic Games: a video-based cross-sectional observational study

OBJECTIVES

To present the fall characteristics of athletes playing wheelchair rugby (WR) and wheelchair basketball (WB) using official videos from the Rio 2016 Paralympic Games and compare the key fall characteristics among the team wheelchair sports event.

METHODS

Eighteen WR and 10 WB game videos for men (MWB) and women (WWB), including 8 teams per sport, were obtained from the official International Paralympic Committee of the Rio 2016 Paralympic Games. The videos were analysed to assess the number of falls, playing time of fall, playing phase, contact with other athletes, the direction of the fall and the body part first in contact with the floor during the fall.

RESULTS

In total, 359 falls (96 for WR, 172 for MWB and 91 for WWB) occurred with a mean of 5.3, 17.2 and 9.1 falls per match, respectively (p<0.05). Significant differences among the three sports were detected in the playing time (p=0.011), presence of contact (p=0.037), direction (p<0.001) and body part first in contact with the floor (p<0.001). For WR, the falls were primarily lateral and caused by contact, occurring in the second half of the match. WB falls tended to be in the first half for women and the second half for men. Most falls were contact falls in the forward direction.

CONCLUSION

By observing the situational details, we described that a number of falls due to contact occurred during these team sports events, especially MWB. In addition, each sport exhibited characteristics attributable to differences in gender, degree of impairment and game rules. The directions of the falls and characteristics of the affected body parts indicate differences in impairments depending on the sport. A fall to the side or back may indicate a risk of injury.

Comparative study of the differences in shoulder muscle activation according to arm rotation angle

BACKGROUND

Scapular muscle exercise is important for patients with shoulder disorders. Distal variance leads to changes in shoulder muscle activation. Here, we aimed to determine whether scapular muscle activation is affected by different arm rotation angles.

METHODS

Overall, 30 healthy men participated in this study. The subjects were asked to keep their arms at 120 degrees of shoulder flexion while holding a 1.0-kg dumbbell in palms down (pronation) and palms up (supination) positions. Electromyography was used to measure anterior, middle, posterior deltoid, serratus anterior, upper, and lower trapezius muscle activation during the task. The muscle activations of each shoulder were compared between the pronation and supination positions.

RESULTS

Anterior deltoid and serratus anterior activations were significantly higher in supination than in pronation (p < .05). Alternatively, posterior deltoid and lower trapezius muscles were significantly more activated in pronation than in supination (p < .05).

CONCLUSION

Scapular muscle activation changed with arm rotation angle. Arm rotation angle should be assessed to estimate scapular muscle activation during exercise and motion analysis in clinical practice.

Effect of 4-week cyclic stretching program on muscle properties and physical performance in healthy adult men

BACKGROUND

The short-term effect of cyclic stretching (CS) has been found to decrease muscle hardness and improve physical performance. However, the long-term effect of CS program was unclear. This study investigated the long-term effect of CS program on muscle properties and physical performance.

METHODS

Eighteen healthy men participated in this study. The participants were assigned randomly to either the CS or control group (9 participants in each group) to conduct 2 min CS of the plantar flexor muscles 5 times a week for 4 weeks. Before and after intervention, the gastrocnemius medialis muscle hardness, muscle-tendon joint (MTJ) angle, and MTJ displacement (ΔMTJ) were measured as indices of muscle properties. In addition, the maximum range of motion of ankle dorsiflexion (ROM max), normalized maximum peak torque of plantar flexor (NPT), vertical jump height, and dynamic postural stability, dynamic postural stability index (DPSI) were measured as indices of physical performance.

RESULTS

The CS program was found to significantly decrease muscle hardness and increase vertical jump height and ROM max, but not to change the MTJ angle, ΔMTJ, NPT, and DPSI.

CONCLUSIONS

The results of our study suggested that long-term CS program was effective in decreasing muscle hardness and increasing vertical jump height.

Quantity and quality of the peroneus longus assessed using ultrasonography in leg with chronic ankle instability

[Purpose] Muscle quantity (e.g., cross-sectional area) and quality (e.g., muscle adipose tissue), which are muscle strength determinants, can be assessed using ultrasonography. The study aimed to investigate the changes in the quantity and quality of the peroneus longus and evaluate evertor strength in legs with chronic ankle instability (CAI). Furthermore, the associations among cross-sectional area, echogenicity, evertor strength, and frequency of ankle sprain were examined. [Participants and Methods] Nine males with CAI in unilateral legs were the voluntary participants in this study. The cross-sectional area of the peroneus longus, echogenicity, and evertor strength were measured for all the participants on the sides with CAI and that without. [Results] No significant difference in cross-sectional area was observed between the sides. Significant differences in echogenicity (higher on the CAI side) and evertor strength (lower on the CAI side) were observed between the sides. In addition, a moderate correlation was observed between echogenicity and increased sprain frequency on both sides. [Conclusion] Muscle adipose tissue increased, evertor strength decreased, and the cross-sectional area remained unchanged on the CAI side. The study results suggested that muscle adipose tissue increases with increasing frequency of ankle sprain.

The effect of different stretching techniques on ankle joint range of motion and dynamic postural stability after landing

BACKGROUND

Stretching improves the flexibility of skeletal muscles, increases the range of motion (ROM) of joints. Stretching is important in prevention of sport-related injuries and influences muscle strength and performance. The effects of Static Stretching (SS) and Cyclic Stretching (CS) have been assessed by examining ROM, muscle power, vertical jump performance. However, the effects on postural control after CS compared with SS does not provide evidence for postural control after landing. The aim of this study was to examine the effects of stretching on the range of motion (ROM) of the ankle joint and dynamic postural stability upon landing on one leg.

METHODS

Twenty healthy subjects participated in this study. Participants were randomly assigned to SS, CS, and control conditions. The ankle was stretched in each condition for two minutes in a standing position. In the assessment of dynamic postural stability, the participant jumped and landed on one leg onto a force platform and the Dynamic Postural Stability Index (DPSI) was measured. Stability indices including those for medial-lateral, anterior-posterior, and vertical stability were calculated. The data were compared among 3 conditions with repeated measures ANOVA and the correlation between ankle range of motion (ROM), DPSI and the maximum vertical ground reaction force (vGRF max) were calculated.

RESULTS

The results indicated that the ROM was significantly greater after SS and CS compared with the control condition. A significant improvement in DPSI was observed after CS.

CONCLUSIONS

We showed that 2 minutes of CS had a positive influence on dynamic postural stability after landing on a single leg. Furthermore, CS may improve balance by increasing postural stability.

[The effect of different working postures while felling a tree with a chain-saw on trunk muscles' activity]

PURPOSE

Many forestry workers who use chain-saws suffer from low back pain. Previous studies have reported that low back pain is related to the working postures while felling a tree with a using chain-saws. However, no previous study has investigated trunk muscle activities during work. The purpose of this study was to clarify the relationship between working postures while holding a chain-saw, and trunk muscles activities as measured by surface electromyography (EMG).

METHOD

Subjects were 10 males who were not forestry workers. Four task postures while holding a chain-saw were tested: standing, 30(o) trunk flexion, 90(o) trunk flexion and half-kneeling. EMG recordings were obtained bilaterally of the lumbar paraspinal (LP) muscles and rectus abdominis (RA) muscles. Raw EMG data were processed by integrating the EMG and normalizing them to %MVC. The paired t-test was used to detect statistical differences in the activities between the right and left LP muscles and RA muscles. One-factor repeated measures ANOVA was used to compare the bilateral LP and RA muscle activities among the 4 different postures. The significance level was set to less than 5%.

RESULTS

In the half-kneeling posture, the right LP muscle activity was 14.7% higher than the left LP muscle activity (p<0.05); however, there were no significant differences in muscle activities among the other postures. The right LP muscle activity of 30(o) trunk flexion posture was 25.6% higher than that of the standing posture, and 14.2% higher than that of half-kneeling posture (p<0.05). The bilateral LP muscle activities of the 90(o) trunk flexion posture were the highest of the 4 postures, 16.7% higher than the half-kneeling posture (p<0.05) right LP muscle activity. There was a tendency of increase in the left LP muscle activity when trunk flexion angle increased, but no significant differences among the 4 postures were found. The bilateral RA muscle activities were low and did not significantly differ among the 4 postures.

CONCLUSIONS

This study showed that when the trunk is flexed, the LP muscle activities change asymmetrically, with the right LP muscle activity increasing significantly compared to the standing posture and the half-kneeing posture, but there was no significant difference in the left LP muscle activity. These results suggest that working postures that involve trunk flexion while felling a tree with a holding chain-saw may lead to increased loading of the LP muscles.

Does shoulder impingement syndrome affect the shoulder kinematics and associated muscle activity in archers?

BACKGROUND

Archery related injuries, such as shoulder impingement syndrome are caused by repeated motion of the shoulder. The aim of this study was to analyze differences in the shoulder kinematics and the associated muscle activity between archers with shoulder impingement and uninjured archery players.

METHODS

Thirty male archers, who were divided into an impingement group and an uninjured group, were included in this study. The angle of scapular elevation, shoulder joint abduction, horizontal extension, and elbow joint flexion as well as the electromyographic activity of the upper trapezius, lower trapezius, deltoid middle, deltoid posterior, biceps brachii, and triceps brachii muscles at the point of stabilization during shooting were measured. Variables differing between impingement and uninjured groups were identified, and a stepwise regression analysis was performed to identify a combination of variables that effectively impingement syndrome.

RESULTS

The results indicated that the angle of scapular elevation was significantly greater than that uninjured group (P<0.05). The angle of horizontal extension in the impingement group was significantly smaller than that in the uninjured group (P<0.05). The angle of elbow flexion in the impingement group was significantly smaller than that in the uninjured group (P<0.05). The levels of upper trapezius and deltoid middle muscle activity were significantly higher in the impingement group, while the level of lower trapezius muscle activity was significantly lower (P<0.05) when compared to the uninjured group. The impingement group had a greater angle of scapular elevation, smaller angle of horizontal extension, smaller angle of elbow flexion, higher the levels of upper trapezius, lower the levels of lower trapezius, higher deltoid middle muscle activity and higher UT/LT ratio (all differences were significant). A logistic model for predicting impingement syndrome showed that UT/LT ratio was significantly related impingement syndrome (P<0.05).

CONCLUSION

The authors concluded that archers with shoulder impingement syndrome exhibit different kinematics and muscle activity compared to uninjured archers. Therefore, in order to prevent shoulder joint impingement during archery, training is necessary what can make lower trapezius muscle activity increased to decrease the UT/LT ratio.