A prospective comparison of lower extremity kinematics and kinetics between injured and non-injured collegiate cross country runners.

Collegiate cross country runners are at risk for running related injuries (RRI) due to high training volume and the potential for aberrant lower extremity biomechanics. However, there is a need for prospective research to determine biomechanical risk factors for RRI. The purpose of this study was to prospectively compare ankle, knee, and hip kinematics and kinetics and ground reaction force characteristics between injured and non-injured cross country runners over a 14-week season. Biomechanical running analyses were conducted on 31 collegiate-cross country runners using a 3-dimensional motion capture system and force plate prior to the start of the season. Twelve runners were injured and 19 remained healthy during the course of the season. Peak external knee adduction moment (KAM), a surrogate for frontal plane knee loading, and peak ankle eversion velocity were greater in runners who sustained an injury compared to those who did not, and no differences were noted in ground reaction force characteristics, or hip kinematics and kinetics. Reducing the KAM and ankle eversion velocity may be an important aspect of preventing RRI.

National Athletic Trainers' Association position statement: anabolic-androgenic steroids.

OBJECTIVE: This manuscript summarizes the best available scholarly evidence related to anabolic-androgenic steroids (AAS) as a reference for health care professionals, including athletic trainers, educators, and interested others. BACKGROUND: Health care professionals associated with sports or exercise should understand and be prepared to educate others about AAS. These synthetic, testosterone-based derivatives are widely abused by athletes and nonathletes to gain athletic performance advantages, develop their physiques, and improve their body image. Although AAS can be ergogenic, their abuse may lead to numerous negative health effects. RECOMMENDATIONS: Abusers of AAS often rely on questionable information sources. Sports medicine professionals can therefore serve an important role by providing accurate, reliable information. The recommendations provide health care professionals with a current and accurate synopsis of the AAS-related research.

Effects of Motorized vs Non-Motorized Treadmill Training on Hamstring/Quadriceps Strength Ratios.

UNLABELLED: Previous literature suggests that muscular involvement and biomechanical changes elicit different responses between overground and treadmill training. The objective of this study was to examine the effects of training on two different treadmill designs on the conventional (CR; concentric only) and functional (FR; eccentric to concentric) hamstring and quadriceps strength ratios. Fifteen men and sixteen women were randomly divided into three groups: motorized (MT), non-motorized (NMT) or control (C). Subjects completed pre and post-test isokinetic concentric and eccentric quadriceps and hamstring testing of both legs. Subjects completed 4 weeks of training on their respective treadmills with mileage increasing ½ mile each week, beginning with 2 miles. The C group did not participate in any training. The CR revealed a significant two way interaction of group x time with MT increasing (pre: 0.80 ± 0.09 to post: 0.84 ± 0.09), NMT decreasing (pre: 0.76 ± 0.13 to post: 0.74 ± 0.10), and C showing no change (pre: 0.79 ± 0.10 to post: 0.79 ± 0.09. The FR revealed a significant two way interaction of speed x sex with the FR increasing as speeds increased for men (60 degrees.s(-1): 1.04 ± 0.11; 180 degrees.s(-1): 1.66 ± 0.27; 300 degrees.s(-1): 2.36 ± 0.45) and women (60 degrees.s(-1): 1.05 ± 0.16; 180 degrees.s(-1): 1.90 ± 0.26; 300 degrees.s(-1): 2.75 ± 0.47) but women increased greater relative to men. Training mode elicited a specific change in concentric hamstring and quadriceps strength resulting in specific changes to the CR; however, neither training mode had an effect on eccentric hamstrings nor the FR. Special attention should be given to the mode of endurance training when the goal is to alter the hamstring/quadriceps CR. KEY POINTS: Specificity of treadmill training had different effects on concentric strength.Specificity of treadmill training had little or no effect on eccentric strength.Conventional and functional strength ratios may give different results based on training mode.Four weeks is long enough for strength results to be apparent in untrained people.

Time course of the effects of static stretching on cycling economy.

Stretching has been implemented as part of the warm-up before physical events and widely thought to promote increased sport performance and decreased injury risk. However, recent research has concluded that static stretching before many exercises inhibits acute power, strength, and sprinting performance. There is little research examining the time course of these effects on moderate intensity cycling. The purpose of this study was to examine the time course of static stretching on cycling economy. The subjects consisted of 5 men and 5 women highly trained endurance cyclists. The first of 3 visits was baseline testing of their cycling VO2max. The second and third visits were either stretching or no stretching before a 30-minute stationary ride at 65% of their VO2max. The stretching condition consisted of four 30-second repetitions of 5 stretches with an average total stretching time of 16 minutes. VO2 demonstrated a significant condition by time interaction with the 5-minute time point being significantly less in the nonstretching condition (32.66 ± 5.35 ml·kg(-1)·min(-1)) than stretching (34.39 ± 5.39 ml·kg(-1)·min(-1)). No other time points were different. Our results demonstrate that static stretching yielded an acute increase in submaximal VO2; therefore, coaches and highly trained endurance cyclists should exclude static stretching immediately before moderate intensity cycling because it reduces acute cycling economy.

Physiological variables and mouthguard use in women during exercise.

Although mouthguards have been found to reduce injury, many athletes choose not to use them because of the belief of negative effects on breathing with mouthguard use. Therefore, this study investigated the effects of mouthguard use on physiological variables in women using a self-adapted mouthguard made for women and a universal self-adapted mouthguard. Eleven subjects (mean +/- SD; age: 22 +/- 3.3 y; height: 159.8 +/- 4.3 cm; body mass: 63.7 +/- 8.9 kg) performed 3 separate maximal cycle ergometer tests with either 1 mouthguard or no mouthguard. Heart rate (HR), rating of perceived exertion (RPE), oxygen consumption VO2), minute ventilation VE), and respiratory exchange ratio (RER) were measured at each exercise intensity and at the end of each test. HR, RPE, and VO2 increased for each mouthguard condition across power levels. VE and RER increased more from 110W to max with the no mouthguard condition than for either mouthguard. However, there was no significant difference in VE or RER at any given power level between mouthguard conditions. The results indicated mouthguard use did not affect HR, RPE, VE, VO2, or RER at any given power level during exercise, including the guard made specifically for women. Therefore, athletes are encouraged to use mouthguards without fear of negative aerobic performance effects.

The effect of short-term VertiMax vs. depth jump training on vertical jump performance.

The ability to generate lower body explosive power is considered an important factor in many athletic activities. Thirty-one men and women, recreationally trained volunteers, were randomly assigned to 3 different groups (control, n = 10; VertiMax, n = 11; and depth jump, n = 10). A Vertec measuring device was used to test vertical jump height pre- and post-training. All subjects trained twice weekly for 6 weeks, performing approximately 140 jumps. The VertiMax group increased elastic resistance and decreased volume each week, while the depth jump group increased both box height and volume each week. The depth jump group significantly increased their vertical jump height (pre: 20.5 +/- 3.98; post: 22.65 +/- 4.09), while the VertiMax (pre: 22.18 +/- 4.31; post: 23.36 +/- 4.06) and control groups (pre: 15.65 +/- 4.51; post: 15.85 +/- 4.17) did not change. These findings suggest that, within the volume and intensity constraints of this study, depth jump training twice weekly for 6 weeks is more beneficial than VertiMax jump training for increasing vertical jump height. Strength professionals should focus on depth jump exercises in the short term over commercially available devices to improve vertical jump performance.