Shock attenuation and impact characteristics for children running at different stride lengths

The purpose of this study was to quantify shock attenuation (SA) and impact characteristics for children (boys and girls) running with different stride lengths (SL). Ten physically active children (10.7+/-1.1 yrs; 40+10.3 kg; 145.2+/-7.3 cm) ran at a constant speed of 3m/s +/- 5% range to complete three stride length conditions: Preferred stride length (PSL), -15%PSL and +15%PSL. During PSL, participants were given no instructions regarding stride length. During -15%PSL and +15%PSL, participants were required to strike markers placed on the floor that resulted in stride length of -15% and +15% of PSL. Ground reaction forces were recorded (1008 Hz) using a force plate (Kistler Instrument) that was mounted flush with the floor in the middle of a 20m runway. Accelerometers (1008 Hz) were securely mounted on the distal aspect of the tibia and on frontal aspect of the forehead. Impact force and shock attenuation in time and frequency domain (calculated as the ratio of head and leg impact accelerations and ratio of power spectral density of head and leg acceleration respectively) were recorded for each running trial. One way repeated measure ANOVA (condition by subject) were performed on the subject means to compare each dependent variable (SA, impact peak (IP), active peak (AP), loading rate (LR)) between three stride length conditions (PSL, -15%PSL, +15%PSL). Results indicated that SA (PSL: 84+/-4.2%, +15%PSL: 87+/-6.4%, -15%PSL: 83+/-6.3%) in the time domain (p = 0.053) and in the frequency domain (PSL: - 38+/-9.3dB, +15%PSL: -39+/-9.9dB, -15%PSL:-40+/-10.8 dB) (p = 0.655) were not significantly different among conditions. The mean values for SA in the time domain across conditions indicated a trend that SA increased with increasing SL. IP (PSL: 16+/-3.1 N/Kg, +15%PSL: 16+/-2.9 N/Kg, -15%PSL: 15+/-2.0 N/Kg) (p = 0.16) and LR (PSL: 736+/-152.4 N/Kg, +15%PSL: 681+/-191.9 N/Kg, -15%PSL: 593+/-136.8 N/Kg) (p = 0.065) were not significantly different across the SL conditions. Planned comparison results for LR indicated that -15%PSL was different (p = 0.025) from +15%PSL. No differences were observed between PSL and +15%PSL (p = 0.413) and -15%PSL and PSL (p = 0.124). However, a trend for LR was observed, that it increased with increasing SL. AP (PSL: 24+/-2.8 N/Kg, +15%PSL: 23+/-3.7 N/Kg, -15%PSL: 23+/-2.6 N/Kg) was significantly different (p = 0.045) between conditions. Planned comparisons identified that PSL was significantly different (p = 0.024) from +15%PSL and from -15%PSL (p = 0.016). No difference was observed between -15%PSL and +15%PSL (p = 0.813). Mean values of the three conditions suggest that AP decreased with changes in SL. The SA, IP, AP and LR have been shown to increase with increasing SL in adults (Derrick et al. 1998). These findings suggest that children may manage impact and shock differently than adults. It is possible that our results may have been influenced by intra-subject variability, which was high among these child runners. Future investigations on child runner performance, focusing on variability as well as comparative adult patterns, are warranted

The Use of Neuromuscular Electrical Simulation in Glenohumeral Unidirectional Instability When an Exercise-Based Approach has Failed: A Case Study

Purpose of this case study was to report the role of neuromuscular electrical stimulation (NMES) to restore strength and normal motion in a patient with unidirectional shoulder instability or glenohumeral internal rotation deficit (GIRD)

Trunk and Lower Extremity Muscle Activity During the Y Balance Test in Healthy Adults

Y balance test kitTM (YBT) is used to measure dynamic balance. YBT is an instrumented version of the Star Excursion Balance test that has Anterior (A), Posteromedial (PM), and Posterolateral (PL) directions. PURPOSE: To determine electromyographic (EMG) activity of the trunk and lower extremity (LE) muscles during YBT performance. METHODS: Surface EMG was collected on 10 males and 10 females healthy adults for the erector spinae (ES), external oblique (EOB), and rectus abdominis (RA) for both ipsilateral (i) and contralateral (c) sides of the stance leg, and gluteus medius (GMED), gluteus maximus (GMAX), Rectus Femoris (RF), Vastus Lateralis (VL), Vastus Medialis (VM), Medial Hamstrings (MH), Biceps Femoris (BF), Anterior Tibialis (AT), and Medial Gastrocnemius (MG) muscles of the stance leg during the performance of the YBT. A 2-way repeated measures analysis of variance (ANOVA) was used to determine the interaction between percentage maximal voluntary isometric contraction and reach directions of the YBT. Separate 1-way repeated measures ANOVA for each muscle was performed to compare the normalized EMG values of the same muscle across the 3 reach directions. Pairwise comparisons were performed using the Sidak post hoc test at an alpha level of .05. RESULTS: The 2-way repeated measures ANOVA with 2 repeated factors, muscle (15 levels) and reach direction (3 levels) interaction was statistically significant (

Lower Extremity and Trunk Electromyographic Muscle Activity During Performance of the Y-Balance Test on Stable and Unstable Surfaces.

Background: The Star Excursion Balance Test (SEBT) has been used as a rehabilitation exercise. To improve its efficacy, efficiency, and method variations, the Y-Balance Test (YBT) with anterior (A), posterolateral (PL), and posteromedial (PM) directions of the SEBT has been recommended. Electromyographic activity has been reported to change when the same task is performed on various surfaces. Hypothesis/Purpose: To compare the EMG activity of trunk and LE muscles during the performance of the YBT on stable and unstable surfaces. Study Design: Cross-Sectional study. Methods: Healthy adults with no history of chronic ankle instability were recruited for the study. Surface electromyography was collected for bilateral (ipsilateral [i] and contralateral [c]) rectus abdominis (RA), external oblique (EOB), erector spinae (ES). While, gluteus maximus (GMAX), gluteus medius (GMED), medial hamstrings (MH), biceps femoris (BF), vastus medialis (VM), rectus femoris (RF), vastus lateralis (VL), anterior tibialis (AT), and medial gastrocnemius (MG) on the stance leg (ipsilateral side), during the performance of the YBT. The unstable surface was introduced using a Thera-Band stability trainer. Differences in electromyography were examined for each reach direction and muscle between the stable and unstable surfaces (p≤ 0.05). Results: Twenty (10 male, 10 female) subjects participated (age: 27.5 ± 4.0 years, height:167 ± 1.0 cm, weight: 66.5 ± 13.0 kg, body fat: 14.1 ± 6.2%). Significantly higher muscle activity for the unstable surface (p0.05) between the stable and unstable surfaces were observed in iRA, cRA, cEOB, VL, and AT for any of the directions of the YBT. Conclusion: An increase in muscle activity was observed during YBT on unstable versus stable surfaces for some muscles. Level of Evidence: 2B

Effect of Stable and Unstable Surfaces on the Serratus Anterior Muscle Activation in a Kinetic-chain Exercise Among Healthy Adults

PURPOSE/HYPOTHESIS: The stabilizing action of the serratus anterior (SA) muscle is vital in maintaining proper scapulothoracic rhythm.1,2 Poor activation of SA muscle could lead to many shoulder dysfunctions.1,3 This warrants for exercises that are best to activate the SA muscle. Kinetic-chain recruitment during exercises has demonstrated increased SA activation due to the myofascial connections between various segments of the body.4–6 Variation of surfaces during an exercise has been shown to alter the muscle recruitment patterns.7–9 The primary purpose of this study was to determine if the unstable surface can influence SA muscle activity during the kinetic chain recruitment while performing the forward punch plus (FPP) exercise. The secondary purpose was to compare the effects of stable versus unstable surface during these exercises. NUMBER OF SUBJECTS: Twenty-one healthy men between the ages of 23 and 35 years with no history of neck and upper extremity (UE) injury or surgery were recruited for the study. MATERIALS/METHODS: Surface electromyographic (EMG) activity of the SA, latissimus dorsi (LD), external oblique (EB) on the dominant, and femoral adductor (FD) muscles on the non dominant side were analyzed in FPP and its 2 variations: FPP with closed chain serape (CS), FPP with open chain serape (OS) on stable and unstable surface. The percentage of maximum voluntary isometric contraction (percent MVIC) for each muscle was compared across 3 exercises using a separate 1-way repeated-measures ANOVA with Sidak pairwise comparison as post hoc test for stable and unstable surface. Multiple paired t tests were run for 3 exercises to compare percent MVIC of stable versus unstable surface for each muscle (P≤.05). RESULTS: Statistically significant main effects existed among all the exercises for the SA, EB, and FD within the same surface but not for LD. Pairwise comparisons within the same surface showed EMG activity of the SA to be significantly higher for the CS and the OS compared to the FPP. Regardless of the surface, there was no significant difference for the SA between the CS and the OS exercises. There was no significant difference in the mean EMG activity of any muscle on a stable surface when compared with the same exercise performed on an unstable surface. CONCLUSIONS: The variations of the FPP exercises designed to incorporate the kinetic chain (CS and OS) does increase the activation of the SA muscle when performed on both stable and unstable surface. However, the type of surface did not influence the activation of any muscle when compared to each other during FPP or its variations. CLINICAL RELEVANCE: The results of this study will further strengthen the concept of recruitment of kinetic chain during exercises. During rehabilitation of the UE muscles, it is recommended to recruit the lower extremity and trunk muscles regardless of the surface person stands on during exercises. Clinicians also need to be aware that adding an unstable surface to an exercise does not always imply higher activation of those muscles

The Effects of Spinal Mobilizations, Manual Stretching, and Exercises in the Treatment of Testicular Pain: A Case Report

The purpose of this case report was to describe the PT management in relieving testicular pain related to genitofemoral nerve entrapment

Gender Differences Between Muscle Activation during Star Excursion Balance Test on Stable versus Unstable Surfaces

INTRODUCTION: Anterior (A), posteromedial (PM), and posterolateral (PL) directions of Star Excursion Balance Test (SEBT) are used for rehabilitation. Adding unstable surface to the task has been reported to change electromyographic (EMG) activity. Studies have also reported differences in EMG between males and females. PURPOSE: To compare EMG of lower extremity (LE) muscles between males and females during SEBT on stable and unstable surfaces. METHODS: Surface EMG was collected on 10 male and 10 female healthy adults for gluteus maximus, gluteus medius (GMED), medial hamstrings, biceps femoris (BF), vastus medialis (VM), rectus femoris (RF), vastus lateralis (VL), anterior tibialis (AT), and medial gastrocnemius (MG) on the stance leg during SEBT. Unstable surface was introduced using TherabandTM stability trainer. Independent t test assessed differences in EMG between males and females for each direction and each muscle during SEBT for both stable and unstable. Paired t tests were run separately for males and females to determine difference in each direction for each muscle between stable and unstable surface with α at 0.05. EMG were reported as the percentage of the maximal voluntary isometric contraction (%MVIC). RESULTS: Females showed significantly higher EMG than males for AT in PL direction (63±14 vs 47±12 %MVIC; P=0.01) on stable surface and A (63±14 vs 47±12 %MVIC; P=0.01) and PL (64±15 vs 47±14 %MVIC; P=0.02) directions on the unstable surface and MG in PM (44±17 vs 25±17 %MVIC; P=0.02) direction on stable surface and A (62±23 vs 37±20 %MVIC; P=0.02), PL (76±29 vs 45±25 %MVIC; P=0.02), and PM (58±26 vs 36±20 %MVIC; P=0.04) directions on unstable surface. EMG was higher for unstable surface in females for VM, RF, and VL in the A direction (p≤0.05) and MG in all three directions (p≤0.05) and in males for GMED, VM, RF, VL in the A direction (p≤0.05) and BF and MG in the PM direction (p≤0.05). CONCLUSION: Females produced higher muscle activation than males for ankle muscles. Adding unstable surface increased LE muscle activation during SEBT. Due to gender differences and surface variability in EMG during SEBT clinicians could consider incorporating both stable and unstable surfaces during rehabilitation especially for women to reduce ankle injuries

Hearts of Dystonia musculorum Mice Display Normal Morphological and Histological Features but Show Signs of Cardiac Stress

Dystonin is a giant cytoskeletal protein belonging to the plakin protein family and is believed to crosslink the major filament systems in contractile cells. Previous work has demonstrated skeletal muscle defects in dystonin-deficient dystonia musculorum (dt) mice. In this study, we show that the dystonin muscle isoform is localized at the Z-disc, the H zone, the sarcolemma and intercalated discs in cardiac tissue. Based on this localization pattern, we tested whether dystonin-deficiency leads to structural defects in cardiac muscle. Desmin intermediate filament, microfilament, and microtubule subcellular organization appeared normal in dt hearts. Nevertheless, increased transcript levels of atrial natriuretic factor (ANF, 66%) β-myosin heavy chain (beta-MHC, 95%) and decreased levels of sarcoplasmic reticulum calcium pump isoform 2A (SERCA2a, 26%), all signs of cardiac muscle stress, were noted in dt hearts. Hearts from two-week old dt mice were assessed for the presence of morphological and histological alterations. Heart to body weight ratios as well as left ventricular wall thickness and left chamber volume measurements were similar between dt and wild-type control mice. Hearts from dt mice also displayed no signs of fibrosis or calcification. Taken together, our data provide new insights into the intricate structure of the sarcomere by situating dystonin in cardiac muscle fibers and suggest that dystonin does not significantly influence the structural organization of cardiac muscle fibers during early postnatal development