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In the effort to reduce concussions in American football, helmet manufacturers are seeking new technologies to reduce peak head impact kinematics. However, the efficacy of these new helmet technologies is unknown. Therefore, the purpose of this study was to evaluate the influence of an intermediary liner on the blunt impact kinematic performance of an American football helmet using a custom test similar to the NOCSAE (ND-081) and NFL linear impactor test methods. Twelve Schutt F7 football helmets with the Radian Diffusion System technology were evaluated under three conditions: with the system (hypothesized to function as a slip plane), without the system, and with a modified system using cloth to cover the hook and loop attachment that, by design, mechanically adheres the system to the comfort liner of the helmet. Helmets were impacted three times at 6 m/s (281 J) at six locations [side, rear boss non-centroidal, rear boss centroidal, rear, front boss, and a random location used for all helmets] using a pneumatic ram. While an effect was found for linear accelerations at the Rear, Rear Boss Center of Gravity, Rear Boss Non-Centroidal, and Random locations, no overall differences between liner conditions were observed for peak resultant linear (p = 0.310) and angular accelerations (p = 0.231), or peak resultant angular velocity (p = 0.127).

Special operation forces participating in mountain warfare/cold weather (MWCW) training have higher energy demands, but adequate fueling is difficult to achieve. The purpose of the study was to determine energy expenditure relative to energy intake and examine fueling patterns during 3 days of MWCW training in Naval Special Warfare Sea, Air, Land (SEAL) Qualification Training (SQT) students. Ten SQT students (age: 23.3 ± 1.8 years, height: 182.3 ± 6.4 cm, and weight: 83.6 ± 4.5 kg) were fitted for heart rate and accelerometer monitors during MWCW training. Total daily energy expenditure was determined using a combination of direct observation and heart rate-VO2regression. Total daily energy intake was collected using the Automated Self-Administered 24 (ASA24) assessment tool. Total daily energy expenditure for river crossing, alpine skills, and mountain patrol were 3,913 ± 293, 4,207 ± 400, and 5,457 ± 828 kcals, respectively. Reported total daily energy intakes were 2,854 ± 657 (river crossing) and 2,289 ± 680 kcals (mountain patrol), producing 1,044 ± 784 and 3,112 ± 1,420 kcal deficits, respectively. SQT students consumed 258 ± 95 g (3.1 ± 1.3 g·kg−1·day−1) of carbohydrates, 130 ± 55 g (1.6 ± 0.7 g·kg−1·day−1) of protein, and 113 ± 39 g (1.4 ± 0.5 g·kg−1·day−1) of fat. MWCW training evolutions elicited high total daily energy expenditure and inadequate energy intake, especially before and during active training sessions, which may lead to decreased work output, early onset fatigue, and increased risk of injury. Increasing total daily energy intake by providing fuel/fluids, primarily carbohydrates, during the planned breaks and “downtime” of each training evolution and focusing on provision of the balance of calories/macronutrients needed for a more complete and expedited recovery over dinner and evening snacks will help bridge the energy gap.

Background The odds of sustaining non-contact musculoskeletal injuries are higher in Special Operations Forces operators than in infantry soldiers. The ankle is one of the most commonly injured joints, and once injured can put individuals at risk for reinjury. The purpose of this study was to determine if any differences in postural stability and landing kinematics exist between operators with a self-reported ankle injury in the past one year and uninjured controls. Methods A total of 55 Special Operations Forces operators were included in this analysis. Comparisons were made between operators with a self-reported ankle injury within one-year of their test date (n = 11) and healthy matched controls (n = 44). Comparisons were also made between injured and uninjured limbs within the injured group. Dynamic postural stability and landing kinematics at the ankle, knee, and hip were assessed during a single-leg jump-landing task. Comparisons were made between groups with independent t-tests and within the injured group between limbs using paired t-tests. Findings There were no significant differences in dynamic postural stability index or landing kinematics between the injured and uninjured groups. Anterior-posterior stability index was significantly higher on the uninjured limb compared to the injured limb within the injured group (P = 0.02). Interpretation Single ankle injuries sustained by operators may not lead to deficits in dynamic postural stability. Dynamic postural stability index and landing kinematics within one year after injury were either not affected by the injuries reported, or injured operators were trained back to baseline measures through rehabilitation and daily activity.