Comparison of Muscle Activity During a Ring Muscle Up and a Bar Muscle Up.

The muscle up (MU) is a variation of a common gymnastics movement that combines a pull up and a dip. It can be performed on a bar (BMU) or a set of rings (RMU). The difference in upper extremity muscle recruitment (MR) between BMU and RMU has not been evaluated. Therefore, the purpose of this study was to compare the MR of select muscles during BMU and RMU. Ten active males (27.6 ± 7.9 years) performed 5 repetitions of BMU and RMU in randomized order. Muscle recruitment of the upper (UT) and lower trapezius (LT), serratus anterior (SA), pectoralis major (PM), latissimus dorsi (LD), triceps brachii (TB), biceps brachii (BB), and forearm flexors (FF) was assessed using electromyography. A 2 × 2 ANOVA (ring vs bar, pull phase vs push phase) with repeated measures was performed for each muscle. Least significant differences post hoc tests were performed when a significant interaction effect occurred. The RMU significantly elicited more muscle activation in the UT (p = 0.007), BB (p = 0.001), and FF (p = 0.001) during the pull phase. The RMU also significantly elicited more muscle activation in the TB (p = 0.025) and BB (p = 0.001) during the push phase. These results suggest that the instability of the RMU primarily increases the required recruitment of the upper limbs but does not significantly change the recruitment of the shoulder stabilizers. Appropriate upper limb development is needed to perform the RMU and the BMU may be a better technique to learn first due to its lower difficulty.

The Effects of Wearing a Portable Media Armband on Muscle Activation of the Biceps Brachii.

Portable media armbands are commonly used among the physically active population. Their effect on muscle function has not been established. The purpose of this study was to determine if muscle activation of the biceps brachii is influenced by wearing a portable media armband during an elbow flexion exercise. Eighteen participants (11 males: age = 22.5 ± 2.1 years, height = 178.3 ± 5.2 cm, mass = 85.0 ± 6.5 kg; 7 females: age = 22.9 ± 2.5 years, height = 168.3 ± 5.7 cm, mass = 72.3 ± 12.2 kg) with no history of upper extremity injury volunteered for the study. Participants performed elbow flexion trials with a hand-held dumbbell with and without wearing a portable media armband. Dumbbell weight was determined by an 8-10 repetition maximum, and the condition was counterbalanced. The average concentric and eccentric phases for five trials for each condition were normalized to a maximum voluntary isometric contraction using electromyography. The independent variable was condition (with-PMAB and without-PMAB). The dependent variable was the muscle activation of the biceps brachii. Mean data for each condition were analyzed using separate paired-samples t-tests for the concentric and eccentric phases (p < 0.05). Statistical analysis revealed a significant difference for the concentric phase (t17 = 2.905; p = 0.010). The with-PMAB condition elicited greater muscle activation (72.57 ± 36.31%) compared to the without-PMAB (63.67 ± 26.2%), with a medium effect size (d = 0.69). There was no statistical difference for the eccentric phase (t17 = 1.964; p = 0.066), and a small effect size (d = 0.46). The increase in muscle activation during the concentric phase is likely due to a change in the muscle properties due to the compressive force applied to the muscle fibers by the portable media armband.

Prehospital Cervical Spine Motion: Immobilization Versus Spine Motion Restriction.

OBJECTIVE: This study aims to evaluate the efficacy of two different spinal immobilization techniques on cervical spine movement in a simulated prehospital ground transport setting. METHODS: A counterbalanced crossover design was used to evaluate two different spinal immobilization techniques in a standardized environment. Twenty healthy male volunteers (age = 20.9 ± 2.2 yr) underwent ambulance transport from a simulated scene to a simulated emergency department setting in two separate conditions: utilizing traditional spinal immobilization (TSI) and spinal motion restriction (SMR). During both transport scenarios, participants underwent the same simulated scenario. The main outcome measures were cervical spine motion (cumulative integrated motion and peak range of motion), vital signs (heart rate, blood pressure, oxygen saturation), and self-reported pain. Vital signs and pain were collected at six consistent points throughout each scenario. RESULTS: Participants experienced greater transverse plane cumulative integrated motion during TSI compared to SMR (F1,57 = 4.05; P = 0.049), and greater transverse peak range of motion during participant loading/unloading in TSI condition compared to SMR (F1,57 = 17.32; P < 0.001). Pain was reported by 40% of our participants during TSI compared to 25% of participants during SMR (χ2 = 1.29; P = 0.453). CONCLUSIONS: Spinal motion restriction controlled cervical motion at least as well as traditional spinal immobilization in a simulated prehospital ground transport setting. Given these results, along with well-documented potential complications of TSI in the literature, SMR is supported as an alternative to TSI. Future research should involve a true patient population.

Electromyographical Comparison of Muscle Activation Patterns Across Three Commonly Performed Kettlebell Exercises.

Lyons, BC, Mayo, JJ, Tucker, WS, Wax, B, and Hendrix, RC. Electromyographical comparison of muscle activation patterns across 3 commonly performed kettlebell exercises. J Strength Cond Res 31(9): 2363-2370, 2017-The purpose of this study was to compare the muscle activation patterns of 3 different kettlebell (KB) exercises using electromyography (EMG). Fourteen resistance-trained subjects completed a 1-arm swing (Swing), 1-arm swing style snatch (Snatch), and a 1-arm clean (Clean) using a self-selected 8 to 10 repetition maximum load for each exercise. Trial sessions consisted of subjects performing 5 repetitions of each KB exercise. Mean EMG was used to assess the muscle activation of the biceps brachii, anterior deltoid, posterior deltoid, erector spinae (ES), vastus lateralis (VL), biceps femoris, contralateral external oblique (EO), and gluteus maximus during each lift using surface electrodes. The mean EMG was normalized using maximal voluntary contractions obtained from manual muscle testing. Repeated-measures analysis of variance revealed a significant difference in the muscle activation patterns of the ES (Swing > Snatch), EO (Snatch, Clean > Swing), and VL (Swing > Clean) across the 3 KB exercises. We conclude that although the KB Swing, Snatch, and Clean are total body exercises, they place different demands on the ES, contralateral EO, and the VL. Therefore, KBs represent an authentic alternative for lifters, and the Swing, Snatch, and Clean are not redundant exercises.

Scapular Upward-Rotation Deficits After Acute Fatigue in Tennis Players.

CONTEXT: Fatigue in overhead athletes reduces shoulder muscular contraction and proprioception. These deficits may lead to alterations in scapular upward rotation, which is associated with multiple chronic shoulder conditions prevalent in tennis players. OBJECTIVE: To identify the effect of a functional fatigue protocol on scapular upward rotation in collegiate male tennis players. DESIGN: Randomized controlled clinical trial. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty healthy male tennis players with no history of shoulder injury completed this study. Participants were divided into 2 groups, experimental (age = 19.4 ± 1.1 years, height = 180.1 ± 8.9 cm, weight = 72.7 ± 11.6 kg) and control (age = 19.6 ± 1.2 years, height = 181.1 ± 6.6 cm, weight = 81.6 ± 13.5 kg). INTERVENTION(S): Participants in the experimental group performed a tennis-serving protocol until the onset of fatigue. Fatigue was defined as a participant reporting a rating of 15 on the Borg Scale of Perceived Exertion and reaching a heart rate of 70% of maximum. Instead of completing the fatigue protocol, control participants rested for an interval time matched to the experimental group. MAIN OUTCOME MEASURE(S): Scapular upward rotation of the dominant arm was measured at rest and at 60°, 90°, and 120° of glenohumeral elevation in the scapular plane. Upward-rotation measurements were taken prefatigue, postfatigue, and at 24, 48, and 72 hours postexercise. Scapular upward-rotation values were calculated as change scores from baseline and analyzed using a 2 × 4 mixed-model analysis of variance. RESULTS: Significant group-by-time interaction effects were found in postfatigue change scores. The experimental group displayed scapular upward-rotation deficits at all testing positions postfatigue (rest: -2.1° ± 1.4°, 60°: -2.2° ± 2.2°, 90°: -3.2° ± 2.1°, 120°: -4.0° ± 1.3°). No differences were observed at 24, 48, or 72 hours after the fatigue protocol. CONCLUSIONS: Fatigue impaired scapular upward rotation in male tennis players, but values returned to baseline within 24 hours. Clinicians should monitor scapular upward rotation in tennis players returning to competition within a day after heavy serving activity.

The Acute Effects of Hold-Relax Proprioceptive Neuromuscular Facilitation With Vibration Therapy on Glenohumeral Internal-Rotation Deficit.

CONTEXT: Clinicians use various stretching techniques to prevent the onset of and treat glenohumeral internal-rotation deficit (GIRD). It is unknown which stretching technique is the most effective. OBJECTIVE: To investigate the acute effects of hold-relax proprioceptive neuromuscular facilitation (PNF) with and without vibration therapy on internal rotation in individuals with GIRD. DESIGN: 2-within (stretch × time) comparison with repeated measures. SETTING: Controlled laboratory. PARTICIPANTS: 11 male current and former overhead athletes (19.8 ± 1.4 y, 184.5 ± 4.5 cm, 91.8 ± 11.6 kg) who presented with GIRD. INTERVENTIONS: At 3 separate sessions, participants performed 1 of 3 randomly assigned stretches: hold-relax PNF (PNF), hold-relax PNF in combination with a whole-body-vibration unit set at 30 Hz (PNF-V), and static stretch (SS). Pretest and posttest maximum passive glenohumeral internal-rotation measurements were taken with a digital protractor. MAIN OUTCOME MEASURES: The dependent variables were the mean glenohumeral internal-rotation measurements taken at the pretest and posttest. The influence of stretch (PNF, PNF-V, and SS) and time (pretest and posttest) on mean glenohumeral internal rotation was compared using a 3 × 2 factorial ANOVA with repeated measures on both variables (P ≤ .05). RESULTS: There was a stretch-by-time interaction (F2,20 = 34.697, P < .001). Post hoc testing revealed that the PNF posttest (73.0° ± 10.4°) was greater than the PNF pretest (60.0° ± 11.8°), the PNF-V posttest (74.7° ± 10.0°) was greater than the PNF-V pretest (57.4° ± 10.4°), and the SS posttest (67.0° ± 10.7°) was greater than the SS pretest (60.1° ± 9.4°). When comparing the posttest values, the PNF-V posttest was greater than the SS posttest. CONCLUSIONS: All 3 stretches (PNF, PNF-V, and SS) resulted in acute increases in glenohumeral internal rotation in individuals presenting with GIRD. The PNF-V stretch resulted in the greatest increase and would be the most clinically beneficial for patients with GIRD.

Head and Trunk Acceleration During Intermediate Transport on Medical Utility Vehicles.

OBJECTIVE: To compare head and trunk acceleration during transport on 2 medical utility vehicles. DESIGN: Within subject. SETTING: Controlled laboratory. PARTICIPANTS: Nineteen male volunteers (21.8 ± 1.4 years, 176.5 ± 5.5 cm, 90.3 ± 16.1 kg). INTERVENTIONS: Participants were secured to a spineboard and stretcher on the Husqvarna HUV 4421DXL ambulance (HUV) and modified John Deere Gator TH (Gator) and driven over synthetic field turf transitioning to concrete slab (interval 1) and concrete slab transitioning to natural grass (interval 2). Three-dimensional (x, y, and z) accelerometers recorded head and trunk acceleration. At each data point, acceleration of the trunk was subtracted from the acceleration of the head and the peak acceleration difference was determined. Independent variables were vehicle (HUV, Gator) and interval (interval 1, interval 2). MAIN OUTCOME MEASURES: The average peak acceleration differences in 3 directions (x, y, z) were analyzed using a 2-factor within analysis of variance (P ≤ 0.05). RESULTS: For x, Gator in interval 2 (28.34 ± 7.45 m/s/s) was greater than HUV in interval 2 (21.87 ± 6.28 m/s/s), and HUV (11.05 ± 3.29 m/s/s) and Gator (12.56 ± 4.32 m/s/s) in interval 1. The HUV in interval 2 was greater than HUV and Gator in interval 1. For z, Gator in interval 2 (22.12 ± 4.8 m/s/s) was greater than HUV in interval 2 (15.21 ± 2.84 m/s/s), and HUV (9.51 ± 3.01 m/s/s) and Gator (12.5 ± 3.78 m/s/s) in interval 1. The HUV in interval 2 was greater than HUV and Gator in interval 1. Gator in interval 1 was greater than HUV in interval 1. CONCLUSIONS: Varying head and trunk accelerations exist in healthy spine-boarded participants during transport on medical utility vehicles dependent on surface and vehicle type. CLINICAL RELEVANCE: Intermediate transport vehicles vary in their ability to mitigate perturbations conveyed to the patient from the terrain travelled over.

Reliability and validity of measuring scapular upward rotation using an electrical inclinometer.

The aim of this study was to assess the reliability and validity of a modified two-dimensional electrical inclinometer to measure scapular upward rotation during static humeral elevation. Numerous techniques have been proposed to qualitatively and quantitatively measure upward rotation of the scapula. These techniques are limited by expense or an inability to be synchronized with other measurements, such as muscle activity and force output. For validity testing, static scapular upward rotation was measured separately with a digital protractor and electrical inclinometer while participants were at rest and 60°, 90° and 120° of humeral elevation in the scapular plane. For reliability testing, either 20 min before or 20 min after validity testing, participants performed the testing positions while measurements were taken with the electrical inclinometer only. Significant correlations existed between the modified electrical inclinometer and digital protractor at all four positions (r>0.996, p<0.001). The electrical inclinometer demonstrated good to excellent intra-rater reliability (ICC(3,1)>0.892, 95%CI: 0.785-0.988 and SEM<1.8°). These results support the use of the electrical inclinometer to measure scapular upward rotation. These findings provide clinicians and researchers with a practical instrument that can accurately measure scapular upward rotation in synchrony with other measurements, such as electromyography and isokinetic data.

Scapular muscle activity in overhead and nonoverhead athletes during closed chain exercises.

OBJECTIVE: To compare scapular muscle activity in healthy overhead and nonoverhead athletes. DESIGN: One between (group) and 1 within (exercise) repeated measures. SETTING: Controlled laboratory environment. PARTICIPANTS: Fifteen overhead sport athletes (10 women and 5 men) and 15 nonoverhead sport athletes (10 women and 5 men). INTERVENTIONS: Subjects completed 5 individual trials of a Cuff Link, standard push-up, and supine pull-up while surface electromyography (EMG) recorded muscle activity of 4 scapular muscles on the throwing dominant side. Mean EMG data were normalized to a maximum voluntary isometric contraction. MAIN OUTCOME MEASURES: Normalized mean EMG. RESULTS: The upper trapezius was significantly more active (F2,56 = 70.118; P < 0.001) during supine pull-up (61.57 ± 29.67%) than during push-up (27.89 ± 16.21%) and Cuff Link (5.50 ± 2.94%). The middle trapezius was significantly more active (F2,56 = 134.192; P < 0.001) during supine pull-up (62.89 ± 24.17%) than during push-up (21.12 ± 13.10%) and Cuff Link (6.59 ± 4.81%). The lower trapezius was significantly more active (F2,56 = 41.326; P < 0.001) during supine pull-up (60.47 ± 34.80%) than during push-up (34.80 ± 30.81%) and Cuff Link (9.67 ± 4.34%). For upper trapezius, middle trapezius, and lower trapezius, the levels of activation during push-up were significantly greater compared with those during Cuff Link. The serratus anterior was significantly more active (F2,56 = 25.652; P < 0.001) during push-up (49.97 ± 18.86%) and Cuff Link (43.81 ± 19.70%) than during supine pull-up (25.52 ± 19.80%). There were no significant influences of group on muscle activation. CONCLUSIONS: Overhead and nonoverhead athletes elicited similar levels of muscle activation. Differences in muscle activation existed within the 3 exercises. Clinicians should consider the muscle of interest when prescribing one of these exercises.

Scapular muscle activity in overhead athletes with symptoms of secondary shoulder impingement during closed chain exercises.

OBJECTIVE: To determine the amount of muscle activation in 4 scapular muscles in overhead athletes with and without a history of secondary shoulder impingement, during 3 upper extremity closed chain exercises. DESIGN: One-between (group), one-within (exercise) repeated measures. SETTING: Controlled laboratory study. PARTICIPANTS: Overhead athletes (n=15; mean age +/- SD, 21.0+/-2.5 y; mean height +/- SD, 176.0+/-7.8 cm; mean weight +/- SD, 76.1+/-13.4 kg) demonstrating with symptoms of shoulder impingement and overhead athletes (n=15; mean age +/- SD, 20.4+/-3.8 y; mean height +/- SD, 174.1+/-9.7 cm; mean weight +/- SD, 73.3+/-11.7 kg) with no shoulder pathologies. INTERVENTIONS: Subjects completed 5 individual trials of a standard push-up, a push-up on an unstable surface, and a revolution on a shoulder rehabilitation device while electromyography (EMG) recorded muscle activity of the serratus anterior, upper trapezius, middle trapezius, and lower trapezius. MAIN OUTCOME MEASURES: The mean EMG data for the 4 muscles from the standard push-up, push-up on an unstable surface, and shoulder rehabilitation device trials were normalized as a percentage of a maximum voluntary isometric contraction for each muscle. RESULTS: There was a statistically significant interaction for the middle trapezius (F(2,56)=3.856; P=.027). The shoulder impingement push-up on an unstable surface (33.76%+/-26.45%) had significantly greater activation compared with the shoulder impingement standard push-up (25.88%+/-13.76%), the shoulder impingement shoulder rehabilitation device (9.40%+/-5.86%), and the nonpathology push-up on an unstable surface (19.49%+/-7.73%). The shoulder impingement standard push-up had significantly greater activation compared with the shoulder impingement shoulder rehabilitation device and nonpathology standard push-up (17.99%+/-7.31%). The nonpathology standard push-up and nonpathology push-up on an unstable surface had significantly greater activation compared with the nonpathology shoulder rehabilitation device (7.95%+/-4.30%). CONCLUSIONS: These results suggest that the muscle activation of the middle trapezius differs in overhead athletes with a history of secondary shoulder impingement compared with those who lack this history during closed chain exercise, as well as within the 3 closed chain exercises. The levels of muscle activation of the serratus anterior and upper trapezius during these closed chain exercises were similar between the 2 groups. These results support the use of closed chain exercises in the rehabilitation process of overhead athletes with secondary shoulder impingement. However, clinicians should consider the muscle(s) of interest when selecting an exercise.

Electromyography of 3 scapular muscles: a comparative analysis of the cuff link device and a standard push-up.

CONTEXT: The Cuff Link is a closed kinetic chain rehabilitation apparatus for the upper extremity. Limited research has established its effectiveness to elicit muscle activation of the scapular muscles. OBJECTIVE: To determine if scapular muscle activation differs in response to 2 upper extremity closed kinetic chain exercises: Cuff Link and standard push-up. DESIGN: A single-group, repeated-measures design. SETTING: Controlled laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-eight healthy individuals (13 women: age = 19.69 +/- 1.55 years, height = 167.44 +/- 9.52 cm, mass = 61.00 +/- 8.79 kg; 15 men: age = 22.00 +/- 3.91 years, height = 181.44 +/- 6.60 cm, mass = 82.36 +/- 13.23 kg) with no history of shoulder or low back injury volunteered to participate in this study. INTERVENTION(S): Participants performed 10 trials of complete revolutions on the Cuff Link and 10 full-weight-bearing push-ups. We controlled trial velocity and randomized order. Trunk and shoulder positions were normalized to the participant's height. Using surface electromyography, we recorded muscle activity of the serratus anterior, middle trapezius, and lower trapezius. Rectified and smoothed electromyography data for the serratus anterior, middle trapezius, and lower trapezius were normalized as a percentage of the maximal voluntary isometric contractions (%MVIC). MAIN OUTCOME MEASURE(S): Mean muscle activity of the serratus anterior, middle trapezius, and lower trapezius. We used paired-samples t tests to analyze the mean data for each condition. The alpha level was adjusted to .016 to avoid a type I error. RESULTS: Middle trapezius %MVIC was greater during push-ups (27.01 +/- 20.40%) than during use of the Cuff Link (11.49 +/- 9.46%) (P = .001). Lower trapezius %MVIC was greater during push-ups (36.07 +/- 18.99%) than during use of the Cuff Link (16.29 +/- 8.64%) (P = .001). There was no difference in %MVIC for the serratus anterior between conditions. CONCLUSIONS: The push-up demonstrated greater middle trapezius and lower trapezius activation levels compared with the Cuff Link. However, the push-up had a high participant failure rate. Because serratus anterior activation levels were similar, the Cuff Link may be an appropriate alternative for individuals lacking the upper body strength to perform a push-up.

Time-of-day influences on static and dynamic postural control.

CONTEXT: Assessment of postural control is used extensively in clinical and research applications. Time of day affects aspects of physical performance, but whether it also affects postural control is unknown. OBJECTIVE: To determine the influence of time of day on static and dynamic postural control. DESIGN: For each static postural control variable, a separate 3-way (day, time, eye) repeated-measures analysis of variance (ANOVA) was performed. For the dynamic postural control variable, a 2-way (day, time) repeated-measures ANOVA was performed. SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty healthy college-aged subjects. INTERVENTION(S): Static and dynamic postural control of each subject was assessed in a laboratory at 10:00, 15:00, and 20:00 on 2 consecutive days. MAIN OUTCOME MEASURE(S): Unilateral static postural control was assessed with eyes open and closed on a forceplate using center-of-pressure velocity in the anterior-posterior and medial-lateral planes as the dependent variables. Dynamic postural control was assessed with the anterior reaching direction of the Star Excursion Balance Test using reach distances normalized to leg length as the dependent variable. RESULTS: For static postural control, velocity scores in both directions were lower at 10:00 than at 15:00 and 20:00 on day 1 (P < .05). For dynamic postural control, normalized reach distance was greater at 10:00 than at 15:00 and 20:00 (P < .05). CONCLUSIONS: Time of day had a consistent influence on dynamic postural control that suggests performance of this task may be better in the morning than in the afternoon or evening. The influence of time of day on static postural control was not as consistent and we feel requires further investigation. These findings have implications for researchers and clinicians when implementing and interpreting postural control testing.