Jan 29, 2015
Bulletin Board

Preventing Muscle Atrophy

New research from the University of Michigan has identified myostatin as a major inhibitor in the growth of muscle tissue following anterior cruciate ligament (ACL) reconstruction surgery. Produced primarily in skeletal cells, myostatin is a hormone that circulates in blood and acts on muscle tissue by binding a cell-bound receptor. According to a study appearing in the June online version of the American Journal of Sports Medicine, the discovery of myostatin’s presence following ACL reconstruction may spur the creation of a drug that would block its negative effects, and result in a quicker return to sport following surgery. “We’ve had several advances in technology to improve the recovery process for an ACL tear, but most patients still experience 30 to 40 percent muscle weakness–and that weakness largely limits the ability to return to the same level of sports,” Christopher L. Mendias, PhD, ATC, the study’s lead author and an Athletic Trainer and Assistant Professor of Orthopaedic Surgery and Molecular and Integrative Physiology at the University of Michigan, said in a school press release. “This is the first study in humans to open the door to a potential therapy to prevent muscle atrophy. We see this as an important step in restoring athletic and functional abilities in the short term, and in preventing osteoarthritis in the long term.”

In the study, patients were examined before and after having ACL reconstruction surgeries following non-contact sports injuries. Prior to the procedure, scientists measured circulating levels of biomarkers for each patient and took objective knee strength calculations. They were then re-evaluated during six postoperative visits. In the end, it was noted that myostatin levels increased significantly early in the postoperative period and returned to pre-surgical baseline levels later in the rehab process. “In the sports world, there’s great concern about the short-term and long-term affect of an ACL tear on not only an athlete’s physical skills and ability to return to play, but also the longevity and health of the knee joint,” Asheesh Bedi, MD, senior author and Assistant Professor in Orthopaedic Surgery at the University of Michigan, stated in the release. “This is the first study to look into the biology of muscle tissue involved in an ACL tear and to show how Myostatin affects the muscle damage we see following surgery.”

To read the study’s abstract, visit: ajs.sagepub.com and type “Changes in Circulating Biomarkers of Muscle Atrophy, Inflammation, and Cartilage Turnover in Patients Undergoing Anterior Cruciate Ligament Reconstruction and Rehabilitation” into the search window.

Knowledge Gap

There appears to be a “striking discrepancy” between college athletic trainers’ perception of their ability to recognize the signs and symptoms of mental health disorders in student-athletes and their actual capacity to do so. This is the conclusion of a study titled “Athletic Trainers’ Understanding of and Experience in Managing Mental Health Disorders,” authored by Andrew Krause, PhD, ATC, from Ohio University and presented at the American College of Sports Medicine meeting in May. The researchers surveyed 211 NCAA athletic trainers about their experience working with athletes with mental health disorders. While 70 percent of respondents said they felt competent in recognizing the signs and symptoms of mental illness, and 63 percent felt confident in their ability to manage mental health disorders acutely, many of them lacked crucial knowledge in this area. For example, when the athletic trainers’ ability to use diagnostic criteria for mental health disorders was assessed, only 44 percent “clearly understood the issues” and only 24 percent were aware of the norms in the most recent Diagnostic and Statistical Manual of Mental Disorders.

“Nearly 90 percent of athletic trainers have encountered and managed at least one athlete with a mental health disorder,” Krause says. “However, the understanding of the spectrum of disorders […] and how to manage patients beyond referral appears to be lacking.

“The take-home message from this study is that mental health diagnosis and management are complex,” he continues. “Entry-level professional competencies ask more of an athletic trainer than to just recognize and refer an athlete with a mental health diagnosis. The approach should be to recognize signs and symptoms, make appropriate clinical and referral decisions, and maintain a strategy throughout the duration of patient-centered care.”

Just Getting Warmed Up

Halftime is usually seen as an opportunity for players to catch their breaths, hydrate, and listen to the coach’s plan for the rest of the game. However, a study published in the February issue of the International Journal of Sports Medicine found that athletes might be better off spending some of this time completing high-intensity, short-duration physical activities to boost performance for the second half. The randomized, crossover study involved eight male soccer players from the Victorian Football Federation in Australia. To simulate the level of exertion achieved during a soccer game, the subjects completed two identical 26-minute sets on a non-motorized treadmill, with a 15-minute “halftime” break in between. During this time, players were either inactive or did “re-warm-ups”–five leg press repetitions or a three-minute soccer passing drill. Measurements for vertical jump (including the flight-time to contraction-time ratio), sprinting endurance, blood lactate concentration, and heart rate were taken before and after each group had completed its halftime activity and immediately following the second treadmill set. Each athlete also took the Loughborough Soccer Passing Test (LSPT) at these times.

The athletes who completed the re-warm-ups were more powerful, more skilled, and faster than the inactive group. For example, when everyone was measured in the vertical jump at the end of halftime, individuals who participated in the leg press activity had a higher flight-time to contraction-time ratio than those in the other two groups. This ratio remained higher for the leg-press subjects when all were tested again after the second 26-minute set of running. Scores for maximum rate-of-force development, repeated-sprint ability, peak velocity, mean velocity, and acceleration were also greater for those who performed the leg press. Players who completed the three-minute passing drill during the break saw their end-of-halftime LSPT scores increase 6.4 percent over their beginning-of-halftime numbers. The LSPT is a timed activity that requires athletes to execute 16 passes and hit a series of targets within a circuit of cones and grids. Points are deducted for inaccurate or poor passes. James Zois, PhD, lead researcher and Lecturer in the College of Sport and Exercise Science at Victoria University, suspects that halftime re-warm-ups may be as beneficial as pregame warm-ups when it comes to improving performance. “The findings encourage coaches…to really scrutinize how they warm up their athletes [before the second half] and to professionalize that component of preparation, as there is real performance-enhancing and injury-preventative potential,” Zois told The Conversation, an Australian news Web site that frequently features sports medicine research.

To view the abstract of the study, “High-Intensity Re-Warm-Ups Enhance Soccer Performance,” visit www.pubmed.gov and search for the title.

Injury Risk & Traction Testing

When it comes to shoe traction, most athletes believe more is better. But is there a point where too much traction negatively affects performance or even increases injury risk? Researchers at the Human Performance Lab at the University of Calgary recently set out to answer this question with help from a unique test subject: a shoe-wearing robot. Traction can be broken down into two classifications: forward, which is when a spike, cleat, or sole digs into the surface to help propel the athlete straight ahead; and rotational, which allows the athlete to move sideways or shift directions. Many researchers have long hypothesized that rotational traction plays a much more significant role injury risk than forward traction, but it’s a difficult theory to test without putting human subjects in harm’s way. To address this dilemma, researchers created a rail-mounted, shoe-wearing robotic tester. Able to move both sideways and straight ahead on a field at various speeds, the robot has “feet” that remain in contact with the ground. To collect data, the feet featured sensors that measured forward and rotational traction levels.

For the study, which was published online in May on the Medicine and Science in Sports and Exercise Web site, researchers borrowed shoes from local high school football players and had the robot calculate each shoe’s forward and rotational traction levels. After testing, the shoes were returned to the players who wore them in the subsequent season, during which time athletic trainers from participating schools tracked non-contact leg injuries. Study leader John Wannop, PhD, a kinesiologist at the University of Calgary, told The New York Times that rates for non-contact ankle, knee, and ligament injuries were highest among players whose shoes provided the most rotational traction. In addition, shoes that provided the most forward traction tended to lead to fewer injuries. Meanwhile, injury rates for shoes worn on grass were similar to those worn on synthetic turf.

Wannop told The Times that to provide ideal athletic performance benefits and minimal injury risk, a shoe should have high translational traction values and relatively low rotational traction values. He added that athletes would do well to avoid models with “multiple large, toothy cleats or rubbery nodules along the outside of the sole,” since they contribute to more rotational traction. Instead, he said, “look for groupings of shorter cleats in the forefoot, which provide safer, more forward-oriented traction.”

For more information on the study, visit www.pubmed.gov and type “Footwear Traction and Lower Extremity Noncontact Injury” into the search window.

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