Electromyography (EMG) Analysis of Multi-Regional Lower Extremity and Trunk Musculature During Sidelying Hip Abduction With Frontal Plane Stabilization

Sidelying hip abduction (SHA) is a common exercise utilized in rehabilitation to strengthen the gluteus medius (GMed). Alterations in the exercise can produce different patterns of muscular activity. No studies have examined the effect of mechanical pelvic stabilization during SHA. This study enrolled 19 participants (male = 11, female = 8) who performed the same SHA exercise under two randomized conditions: standard and with a mechanical block to prevent frontal-plane movement. Electromyographic amplitudes during exercise were obtained through surface electrodes and compared against maximum voluntary isometric contraction (MVIC) testing: GMed, gluteus maximus, biceps femoris, tensor fascia latae, quadratus lumborum, and vastus lateralis. While no significant differences were found in GMed activity during SHA with or without pelvic stabilization, reduced concomitant activation of other musculature was observed, potentially producing a more isolated exercise for the GMed with less compensatory activity.

Optimal Blood Flow Restriction Occlusion Pressure for Shoulder Muscle Recruitment With Upper Extremity Exercise

BACKGROUND

As blood flow restriction (BFR) utilization continues to rise, it is crucial to define optimal parameters for use. Currently unknown are the effects of occlusion level during BFR on muscle activity in the proximal shoulder.

PURPOSE/HYPOTHESIS

The purpose of this study was to compare electromyographic amplitude (EMGa) of shoulder musculature during exercise using limb occlusion percentages (LOPs). The authors hypothesized that EMGa would increase concurrently with occlusion.

STUDY DESIGN

Controlled laboratory study.

METHODS

α Fifteen healthy adults were recruited and underwent 4 experimental sessions, performing 3 common rotator cuff exercises at low intensity (20% maximal strength) to failure in the following order: cable external rotation (ER), cable internal rotation (IR), and dumbbell scaption. Exercises were completed at a different occlusion pressure (0%, 25%, 50%, and 75% LOP- order randomized) applied at the proximal arm. EMGa was recorded from shoulder musculature proximal to the occlusion site and averaged across 5-repetition intervals and overall for the first 30 repetitions. An analysis of variance repeated on occlusion pressure followed by a Bonferroni post hoc test was used to compare EMGa, repetitions to fatigue, and ratings of discomfort (visual analog scale [VAS], 0-10) between occlusion pressures. The type 1 error was set at α = .05 for all analyses.

RESULTS

Significant effects of the occlusion level on shoulder muscle EMGa were observed for all exercises (P < .05) with diminishing returns above 50% LOP (overall). For ER, elevations in EMGa were observed at ≥50% LOP for the anterior deltoid, middle deltoid, infraspinatus, and trapezius compared with 0% LOP (P < .05). For IR, elevations in EMGa were observed at ≥25% LOP for the anterior deltoid and trapezius compared with 0% LOP (P < .05). For the teres minor, a significant elevation in EMGa occurred at 75% LOP compared with 0%, 25%, and 50% LOP (P < .05). A decrease in EMGa was observed at ≥50% LOP compared with 0% LOP for the posterior deltoid (P < .05). For scaption, an increase in EMGa was observed at ≥25% LOP for the infraspinatus and teres minor muscles, at 75% LOP for the posterior deltoid, and at ≥50% LOP for the trapezius compared with 0% LOP (P < .05). Decreases in repetitions to failure relative to 0% LOP were observed at 75% LOP for ER (0%: 47 ± 5; 75%: 40 ± 2; P = .034), IR (0%: 82 ± 10; 75%: 64 ± 5; P = .017), and scaption (0%: 85 ± 9; 75%: 64 ± 6; P < .001). A significant linear increase in discomfort was observed for all exercises with increasing occlusion pressures (VAS: 0-10, 0% → 75% LOP; ER: 2.2 ± 0.4 → 7.2 ± 0.3; IR: 1.3 ± 0.2 → 6.1 ± 0.6; scaption: 1.3 ± 0.4 → 6.1 ± 0.4; P < .01).

CONCLUSION

There are several differences in muscle activation about the shoulder based on exercise and occlusion when utilizing BFR. Increasing the percentage of limb occlusion leads to heightened EMGa with diminished returns past 50% LOP when considering muscle activation, discomfort, and achievable exercise volume.

CLINICAL RELEVANCE

These findings may be used to refine upper extremity BFR guidelines.

Rotator cuff training with upper extremity blood flow restriction produces favorable adaptations in Division IA collegiate pitchers: a randomized trial

BACKGROUND

Recent evidence indicates that combined upper extremity blood flow restriction (BFR, applied distally to the shoulder) and low-load resistance exercise (LIX) augments clinically meaningful responses in shoulder region tissues proximal to the occlusion site. The purpose of this investigation was to determine the efficacy of BFR-LIX for the shoulder when added to standard offseason training in Division IA collegiate baseball pitchers. We hypothesized that BFR-LIX would augment training-induced increases in shoulder-region lean mass, rotator cuff strength, and endurance. As secondary outcomes, we sought to explore the impact of BFR-LIX rotator cuff training on pitching mechanics.

METHODS

Twenty-eight collegiate baseball pitchers were randomized into 2 groups (BFR^N=15, NOBFR^N=13) that, in conjunction with offseason training, performed 8wks of shoulder LIX [Throwing arm only; 2/wk, 4 sets (30/15/15/fatigue), 20%isometric max] using 4 exercises [cable external and internal rotation (ER/IR), dumbbell scaption, and side-lying dumbbell ER]. The BFR group also trained with an automated tourniquet on the proximal arm (50%-occlusion). Regional lean mass (dual-energy x-ray absorptiometry), rotator cuff strength (dynamometry: IR0&90, ° ER0&90, ° Scaption, Flexion), and fastball biomechanics were assessed pre- and post-training. Achievable workload (sets × reps × resistance) was also recorded. An ANCOVA (covaried on baseline measures) repeated on training timepoint was used to detect within-group and between-group differences in outcome measures (α=0.05). For significant pairwise comparisons, effect size (ES) was calculated using a Cohen's d statistic and interpreted as: 0-0.1, negligible(N); 0.1-0.3, small(S); 0.3-0.5, moderate(M); 0.5-0.7, large(L); >0.7, very large(VL).

RESULTS

Following training, the BFR group experienced greater increases in shoulder-region lean mass [BFR: ↑227±60g, NOBFR: ↑75±37g, P=0.018, ES=1.0(VL)] and isometric strength for IR90° (↑2.4±2.3kg, P=0.041, ES=0.9VL). The NOBFR group experienced decreased shoulder flexion (↓1.6±0.8kg, P=0.007, ES=1.4VL) and IR at 0°(↓2.9±1.5kg, P=0.004, ES=1.1VL). The BFR group had a greater increase in achievable workload for the scaption exercise (BFR: ↑190±3.2kg, NOBFR: ↑90±3.3kg, P=0.005, ES=0.8VL). Only the NOBFR group was observed to experience changes in pitching mechanics following training with increased shoulder external rotation at lead foot contact (↑9.0°±7.9, P=0.028, ES=0.8VL) as well as reduced forward (↓3.6°±2.1, P=0.001, ES=1.2VL) and lateral (↓4.6°±3.4, P=0.007, ES=1.0VL) trunk tilt at ball release.

CONCLUSION

BFR-LIX rotator cuff training performed in conjunction with a collegiate offseason program augments increases in shoulder lean mass as well as muscular endurance while maintaining rotator cuff strength and possibly pitching mechanics in a manner that may contribute to favorable outcomes and injury prevention in baseball pitching athletes.

Blood Flow Restriction Enhances Rehabilitation and Return to Sport: The Paradox of Proximal Performance

The use of blood flow restriction (BFR) within rehabilitation is rapidly increasing as further research is performed elucidating purported benefits such as improved muscular strength and size, neuromuscular control, decreased pain, and increased bone mineral density. Interestingly, these benefits are not isolated to structures distal to the occlusive stimulus. Proximal gains are of high interest to rehabilitation professionals, especially those working with patients who are limited due to pain or postsurgical precautions. The review to follow will focus on current evidence and ongoing hypotheses regarding physiologic responses to BFR, current clinical applications, proximal responses to BFR training, potential practical applications for rehabilitation and injury prevention, and directions for future research. Interestingly, benefits have been found in musculature proximal to the occlusive stimulus, which may lend promise to a greater variety of patient populations and conditions. Furthermore, an increasing demand for BFR use in the sports world warrants further research for performance research and recovery.

LEVEL OF EVIDENCE

Level V, expert opinion.

Relationship Between Pitch Volume and Subjective Report of Injury in High School Female Fast-Pitch Softball Pitchers

BACKGROUND

The relationship between pitch volume and injury is well-represented within baseball literature. However, the impact of softball pitch volume on injury epidemiology is limited.

HYPOTHESIS

The purpose was to determine if increased pitch volumes in high school-aged softball pitchers are related to increased rates of subjectively reported pain/injury. We hypothesized that pitchers with increased volumes would have higher pain/injury rates.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 28 female softball pitchers (aged 14-18 years) completed an online survey of questions pertaining to pitching history, pitch volume, and subjective report of pain or injury in the back, shoulder, and elbow. An independent-samples t test was used to (1) compare pitch volumes in those who reported pain in individual body regions (shoulder, elbow, back) compared with those who did not; (2) compare pitch volumes in those who reported pain in 0 or 1 of the regions of interest compared with 2 or 3 regions; and (3) compare the reported percentage of the past year that players reported playing through pain in players who averaged >85 compared with <85 pitches per game. Chi-square analysis was used to compare those who pitched either >85 or <85 pitches per game with regard to frequency of shoulder pain, elbow pain, back pain, seeking of medical attention, and actual injury diagnosis. Type I error was set at α = 0.05.

RESULTS

Weekly and yearly pitch counts were higher in those reporting pain or injury (YES) than those who did not (NO) in the shoulder (pitches per week: NO = 219 ± 35; YES = 429 ± 101; P = 0.027) (pitches per year: NO = 8876 ± 946; YES = 19,195 ± 4944; P = 0.022) and back (pitches per week: NO = 188 ± 16; YES = 426 ± 90; P = 0.014) (pitches per year: NO = 8334 ± 793; YES = 18,252 ± 4340; P = 0.027). Similar results were observed for those with pain or injury reported in 2 or 3 regions compared with 0 or 1 regions (pitches per week: NO = 220 ± 38; YES = 414 ± 95; P = 0.039) (pitches per year: NO = 8765 ± 1010; YES = 18,661 ± 4623; P = 0.028). Those reporting shoulder pain or injury also reported higher pitch counts per game (NO = 71.4 ± 5.2; YES = 83 ± 4; P = 0.049), and those reporting back pain also reported playing more games per week (NO = 2.7 ± 0.2; YES = 5.2 ± 1.1; P = 0.034). Those with pitch counts of >85/game were more than twice as likely to see a physician regarding pain/injury (P = 0.027) and reported playing through pain a higher percentage of the year (>85, 49.3% ± 10%; <85, 25.2% ± 6%; P < 0.05).

CONCLUSION

High pitching volumes commonly prevalent in high school-aged softball pitchers may be associated with increased pain/injury and appear related to cumulative volume.

CLINICAL RELEVANCE

This study provides recommendations for cumulative pitch volume guidelines in softball pitchers.

Blood Flow Restriction Training for the Shoulder: A Case for Proximal Benefit

BACKGROUND

Although blood flow restriction (BFR) is becoming increasingly popular in physical therapy and athletic training settings, little is known about the effects of BFR combined with low-intensity exercise (LIX) on muscles proximal to the site of occlusion.

HYPOTHESIS/PURPOSE

Determine whether LIX combined with BFR applied distally to the shoulder on the brachial region of the arm (BFR-LIX) promotes greater increases in shoulder lean mass, rotator cuff strength, endurance, and acute increases in shoulder muscle activation compared with LIX alone. We hypothesized that BFR-LIX would elicit greater increases in rotator cuff strength, endurance, and muscle mass. We also hypothesized that the application of BFR would increase EMG amplitude in the shoulder muscles during acute exercise.

STUDY DESIGN

Controlled laboratory study.

METHODS

32 healthy adults were randomized into 2 groups (BFR group, 13 men, 3 women; No-BFR group, 10 men, 6 women) who performed 8 weeks of shoulder LIX (2 times per week; 4 sets [30/15/15/fatigue]; 20% maximum) using common rotator cuff exercises (cable external rotation [ER], cable internal rotation [IR], dumbbell scaption, and side-lying dumbbell ER). The BFR group also trained with an automated tourniquet placed at the proximal arm (50% occlusion). Regional lean mass (dual-energy x-ray absorptiometry), isometric strength, and muscular endurance (repetitions to fatigue [RTF]; 20% maximum; with and without 50% occlusion) were measured before and after training. Electromyographic amplitude (EMGa) was recorded from target shoulder muscles during endurance testing. A mixed-model analysis of covariance (covaried on baseline measures) was used to detect within-group and between-group differences in primary outcome measures (α = .05).

RESULTS

The BFR group had greater increases in lean mass in the arm (mean ± 95% CI: BFR, 175 ± 54 g; No BFR, -17 ± 77 g; P < .01) and shoulder (mean ± 95% CI: BFR, 278 ± 90 g; No BFR, 96 ± 61 g; P < .01), isometric IR strength (mean ± 95% CI: BFR, 2.9 ± 1.3 kg; No BFR, 0.1 ± 1.3 kg; P < .01), single-set RTF volume (repetitions × resistance) for IR (~1.7- to 2.1-fold higher; P < .01), and weekly training volume (weeks 4, 6-8, ~5%-22%; P < .05). Acute occlusion (independent of group or timepoint) yielded increases in EMGa during RTF (~10%-20%; P < .05).

CONCLUSION

Combined BFR-LIX may yield greater increases in shoulder and arm lean mass, strength, and muscular endurance compared with fatiguing LIX alone during rotator cuff exercises. These findings may be due, in part, to a greater activation of shoulder muscles while using BFR.

CLINICAL RELEVANCE

The present study demonstrates that BFR-LIX may be a suitable candidate for augmenting preventive training or rehabilitation outcomes for the shoulder.

The Role of Fatigue in Return to Sport Testing Following Anterior Cruciate Ligament Reconstruction

BACKGROUND

Fatigue may play a role in anterior cruciate ligament (ACL) injury, but has not been incorporated into objective test batteries for return to sport decisions following ACL reconstruction (ACLR) surgery. The effect of fatigue on muscle function and performance following surgery and rehabilitation has been poorly studied.

PURPOSE/HYPOTHESIS

The purpose of this study was to assess the effect of fatigue on performance of various hop tests used in clinical rehabilitation settings by examining LSI scores. The authors hypothesized that participants will have worse limb symmetry index scores following the fatigue protocol and that the operative limb (ACLR) will have a greater decline in function than the non-operative limb (CON).

STUDY DESIGN

Cross-Sectional Study.

METHODS

Participants (n=21 [Male = 15, Female = 6]; AGE = 24.6 ± 9.3) were at least six months post ACLR and in rehabilitation. Testing was performed over two separate sessions in either a non-fatigued (NFS) or fatigued state (FS). In the FS, individuals performed a series of exercises to exhaust muscular endurance, strength, and power systems, after which they performed as battery of seven hop tests (single hop for distance, triple hop for distance, crossover hop for distance, 6-meter timed hop, lateral rotation hop for distance, medial rotation hop for distance, and vertical jump for height). A 2(limb) x 2(time) ANOVA was used to compare limbs between each state.

RESULTS

Differences between limbs (CON vs ACLR) were observed for all hop tests in the NFS whereby the ACLR limb was observed to have reduced performance (↓5.4-9.1%, p <0.05). When tested in the FS, significant differences in performance between limbs remained for only the crossover (↓4.9%), medial rotation (↓7.1%), lateral rotation (↓5.5%), and vertical hop (↓10.0%)(p<0.05). When comparing the NFS and FS states, only the CON limb was observed to have significant decreases in performance of the Triple Hop (↓7.4%), Crossover (↓8.7%), and Lateral Rotation (↓5.2%)(p<0.05).

CONCLUSIONS

Following ACL reconstruction, there appears to be a greater loss in jump performance in the CON limb in the FS. These findings suggest it may be crucial to consider and assess the endurance of both limbs rather than just the ACLR limb when determining readiness for return to play.

LEVEL OF EVIDENCE

Level 3.

THEORETICAL APPLICATIONS OF BLOOD FLOW RESTRICTION TRAINING IN MANAGING CHRONIC ANKLE INSTABILITY IN THE BASKETBALL ATHLETE

Chronic ankle instability (CAI) is a common dysfunctional state in the basketball population accompanied by pain, weakness and proprioceptive deficits which greatly affect performance. Research evidence has supported the use of blood flow restriction (BFR) training as an effective treatment strategy for improving muscle strength, hypertrophy and function following injury in a variety of patient populations. In managing CAI, it is important to address proximal and distal muscle weakness, pain, and altered proprioception to reduce the likelihood of re-occurring ankle injury. The ability to mitigate acute and cumulative strength and muscle volume losses through the integration of BFR after injury has been supported in research literature. In addition, applications of BFR training for modulating pain, improving muscle activation and proximal muscle strength have recently been suggested and may provide potential benefit for athletes with CAI. The purpose of this clinical commentary is to discuss background evidence supporting the implementation of blood flow restriction training and use a theoretical model for managing CAI as well as to suggest novel treatment strategies using this method.

LEVEL OF EVIDENCE

5.

Reliability and validity of a smartphone pulse rate application for the assessment of resting and elevated pulse rate

Purpose/hypothesis: This study was designed to investigate the test-retest reliability, concurrent validity, and the standard error of measurement (SEm) of a pulse rate assessment application (Azumio®'s Instant Heart Rate) on both Android® and iOS® (iphone operating system) smartphones as compared to a FT7 Polar® Heart Rate monitor. Number of subjects: 111.

MATERIALS/METHODS

Resting (sitting) pulse rate was assessed twice and then the participants were asked to complete a 1-min standing step test and then immediately re-assessed. The smartphone assessors were blinded to their measurements.

RESULTS

Test-retest reliability (intraclass correlation coefficient [ICC 2,1] and 95% confidence interval) for the three tools at rest (time 1/time 2): iOS® (0.76 [0.67-0.83]); Polar® (0.84 [0.78-0.89]); and Android® (0.82 [0.75-0.88]). Concurrent validity at rest time 2 (ICC 2,1) with the Polar® device: IOS® (0.92 [0.88-0.94]) and Android® (0.95 [0.92-0.96]). Concurrent validity post-exercise (time 3) (ICC) with the Polar® device: iOS® (0.90 [0.86-0.93]) and Android® (0.94 [0.91-0.96]). The SEm values for the three devices at rest: iOS® (5.77 beats per minute [BPM]), Polar® (4.56 BPM) and Android® (4.96 BPM).

CONCLUSIONS

The Android®, iOS®, and Polar® devices showed acceptable test-retest reliability at rest and post-exercise. Both the smartphone platforms demonstrated concurrent validity with the Polar® at rest and post-exercise.

CLINICAL RELEVANCE

The Azumio® Instant Heart Rate application when used by either platform appears to be a reliable and valid tool to assess pulse rate in healthy individuals.