ABSTRACT
Introduction
Strength and power asymmetries of >10% may negatively impact physical function.
Methods
Twenty‐four healthy participants, 30–60 years of age, were assessed for muscle power ...asymmetry during isokinetic knee extension and ground reaction force asymmetry during chair‐rise and vertical jump tasks. Neuromuscular activation asymmetry and coactivation of vastus lateralis (VL) and biceps femoris (BF) were assessed in each condition. Symmetric (SG) and asymmetric (AG) groups were identified using a 10% knee extension power asymmetry criterion.
Results
The AG had greater chair‐rise rate of force development asymmetry (P = 0.003, d = 1.29), but a similar chair‐rise and vertical jump peak force asymmetry as the SG. Large group effects were found for VL activation asymmetry during knee extension (P = 0.047, d = 0.87), BF activation asymmetry during vertical jump (P = 0.015, d = 1.12), and strong leg coactivation during vertical jump (P = 0.028, d = 0.96).
Conclusions
Compensation for muscle power asymmetry may occur during functional tasks, potentially through differential activation of strong and weak leg muscles. Muscle Nerve 56: 495–504, 2017
To test a helmetless-tackling behavioral intervention for reducing head impacts in National Collegiate Athletic Association Division I football players.
Randomized controlled clinical trial.
Football ...field.
Fifty collegiate football players (intervention = 25, control = 25).
The intervention group participated in a 5-minute tackling drill without their helmets and shoulder pads twice per week in the preseason and once per week through the season. During this time, the control group performed noncontact football skills.
Frequency of head impacts was recorded by an impact sensor for each athlete-exposure (AE). Data were tested with a 2 × 3 (group and time) repeated-measures analysis of variance. Significant interactions and main effects (P < .05) were followed with t tests.
Head impacts/AE decreased for the intervention group compared with the control group by the end of the season (9.99 ± 6.10 versus 13.84 ± 7.27, respectively). The intervention group had 30% fewer impacts/AE than the control group by season's end (9.99 ± 6.10 versus 14.32 ± 8.45, respectively).
A helmetless-tackling training intervention reduced head impacts in collegiate football players within 1 season.
Participation in any sport activity carries risk of cervical spine trauma, but certain activities have a higher risk than others, and hence, demand concerted efforts in developing prevention ...strategies. Prevention often includes efforts surrounding education of stakeholders, creating or modifying rules, and specific policies adopted for decreasing such risk. Stakeholders include sport clinicians, participants, coaches, parents, league administrators, officials, and the public. Thus, both athlete-specific and setting-specific factors must be considered and controlled to the extent possible for a multipronged approach for decreasing cervical spine injury risk. The effectiveness of certain strategies put into place in collision sports, such as American football, rugby, and ice hockey, is reviewed to illustrate this approach. Some research evidence exists that either has informed a strategy, or validated its effectiveness after the fact. More research of a higher level needs to be conducted in all sports to continue to contain the risk of cervical spine trauma to the fullest extent possible.
To present recommendations for the prevention and screening, recognition, and treatment of the most common conditions resulting in sudden death in organized sports.
Cardiac conditions, head injuries, ...neck injuries, exertional heat stroke, exertional sickling, asthma, and other factors (eg, lightning, diabetes) are the most common causes of death in athletes.
These guidelines are intended to provide relevant information on preventing sudden death in sports and to give specific recommendations for certified athletic trainers and others participating in athletic health care.
To provide evidence-based recommendations for reducing the prevalence of head-first contact behavior in American football players with the aim of reducing the risk of head and neck injuries.
In ...American football, using the head as the point of contact is a persistent, well-documented, and direct cause of catastrophic head and cervical spine injury. Equally concerning is that repeated head-impact exposures are likely to result from head-first contact behavior and may be associated with long-term neurocognitive conditions such as dementia, depression, and chronic traumatic encephalopathy.
The National Athletic Trainers' Association proposes 14 recommendations to help the certified athletic trainer, allied health care provider, coach, player, parent, and broader community implement strategies for reducing the prevalence of head-first contact in American football.
Current treatment recommendations for American football players with exertional heatstroke are to remove clothing and equipment and immerse the body in cold water. It is unknown if wearing a full ...American football uniform during cold-water immersion (CWI) impairs rectal temperature (Trec) cooling or exacerbates hypothermic afterdrop.
To determine the time to cool Trec from 39.5°C to 38.0°C while participants wore a full American football uniform or control uniform during CWI and to determine the uniform's effect on Trec recovery postimmersion.
Crossover study.
Laboratory.
A total of 18 hydrated, physically active, unacclimated men (age = 22 ± 3 years, height = 178.8 ± 6.8 cm, mass = 82.3 ± 12.6 kg, body fat = 13% ± 4%, body surface area = 2.0 ± 0.2 m(2)).
Participants wore the control uniform (undergarments, shorts, crew socks, tennis shoes) or full uniform (control plus T-shirt; tennis shoes; jersey; game pants; padding over knees, thighs, and tailbone; helmet; and shoulder pads). They exercised (temperature approximately 40°C, relative humidity approximately 35%) until Trec reached 39.5°C. They removed their T-shirts and shoes and were then immersed in water (approximately 10°C) while wearing each uniform configuration; time to cool Trec to 38.0°C (in minutes) was recorded. We measured Trec (°C) every 5 minutes for 30 minutes after immersion.
Time to cool from 39.5°C to 38.0°C and Trec.
The Trec cooled to 38.0°C in 6.19 ± 2.02 minutes in full uniform and 8.49 ± 4.78 minutes in control uniform (t17 = -2.1, P = .03; effect size = 0.48) corresponding to cooling rates of 0.28°C·min(-1) ± 0.12°C·min(-1) in full uniform and 0.23°C·min(-1) ± 0.11°C·min(-1) in control uniform (t17 = 1.6, P = .07, effect size = 0.44). The Trec postimmersion recovery did not differ between conditions over time (F1,17 = 0.6, P = .59).
We speculate that higher skin temperatures before CWI, less shivering, and greater conductive cooling explained the faster cooling in full uniform. Cooling rates were considered ideal when the full uniform was worn during CWI, and wearing the full uniform did not cause a greater postimmersion hypothermic afterdrop. Clinicians may immerse football athletes with hyperthermia wearing a full uniform without concern for negatively affecting body-core cooling.
To evaluate a behavioral intervention to reduce head impact exposure in youth playing American football.
Nested randomized controlled trial.
Participants, ages 14–17 years, wore head impact sensors ...(SIM-G™) during two seasons of play. Those randomized to the intervention group underwent weekly tackling/blocking drills performed without helmets (WoH) and shoulder pads while the control group trained as normal, matching frequency and duration. Research personnel provided daily oversight to maintain fidelity. Head impact frequency (≥10g) per athlete exposure (ImpAE) was analyzed over time (two 11-week seasons) using mixed effect models or ANCOVA. Secondary outcomes included exposure-type (training, game) and participation level (entry-level versus upper-level secondary education).
One-hundred fifteen participants (59 WoH, 56 control) met compliance criteria, contributing 47,382 head impacts and 10,751 athlete exposures for analysis. WoH had fewer ImpAE during games compared to control participants at weeks 4 (p=0.0001 season 1, p=0.0005 season 2) and 7 (p=0.0001 both seasons). Upper-level WoH participants had less ImpAE during games than their matched controls at weeks 4 (p=0.017 and p=0.026) and 7 (p=0.037 and p=0.014) in both seasons, respectively. Upper-level WoH also had fewer ImpAE during training at week 7 (p=0.015) in season one.
Tackling and blocking drills performed without a helmet during training reduced the frequency of head impacts during play, especially during games. However, these differences disappeared by the end of the season. Future research should explore the frequency of behavioral intervention and a dose-response relationship considering years of player experience.
ClinicalTrials.gov # NCT02519478.
This study aims to evaluate the efficacy of two different spinal immobilization techniques on cervical spine movement in a simulated prehospital ground transport setting.
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.
Participants experienced greater transverse plane cumulative integrated motion during TSI compared to SMR (F
= 4.05; P = 0.049), and greater transverse peak range of motion during participant loading/unloading in TSI condition compared to SMR (F
= 17.32; P < 0.001). Pain was reported by 40% of our participants during TSI compared to 25% of participants during SMR (χ
= 1.29; P = 0.453).
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.
Introduction
Sports participation is among the leading causes of catastrophic cervical spine injury (CSI) in the United States. Appropriate prehospital care for athletes with suspected CSIs should be ...available at all levels of sport. The goal of this project was to develop a set of best-practice recommendations appropriate for athletic trainers, emergency responders, sports medicine and emergency physicians, and others engaged in caring for athletes with suspected CSIs.
Methods
A consensus-driven approach (RAND/UCLA method) in combination with a systematic review of the available literature was used to identify key research questions and develop conclusions and recommendations on the prehospital care of the spine-injured athlete. A diverse panel of experts, including members of the National Athletic Trainers' Association, the National Collegiate Athletic Association, and the Sports Institute at UW Medicine participated in 4 Delphi rounds and a 2-day nominal group technique meeting. The systematic review involved 2 independent reviewers and 4 rounds of blinded review.
Results
The Delphi process identified 8 key questions to be answered by the systematic review. The systematic review comprised 1544 studies, 49 of which were included in the final full-text review. Using the results of the systematic review as a shared evidence base, the nominal group technique meeting created and refined conclusions and recommendations until consensus was achieved.
Conclusions
These conclusions and recommendations represent a pragmatic approach, balancing expert experiences and the available scientific evidence.
To compare head and trunk acceleration during transport on 2 medical utility vehicles.
Within subject.
Controlled laboratory.
Nineteen male volunteers (21.8 ± 1.4 years, 176.5 ± 5.5 cm, 90.3 ± 16.1 ...kg).
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).
The average peak acceleration differences in 3 directions (x, y, z) were analyzed using a 2-factor within analysis of variance (P ≤ 0.05).
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.
Varying head and trunk accelerations exist in healthy spine-boarded participants during transport on medical utility vehicles dependent on surface and vehicle type.
Intermediate transport vehicles vary in their ability to mitigate perturbations conveyed to the patient from the terrain travelled over.
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