Meleesa F. Wohleber

Landing Kinematics and Kinetics at the Knee During Different Landing Tasks

CONTEXT   Several tasks have been used to examine landing biomechanics for evaluation and rehabilitation, especially as related to anterior cruciate ligament injuries. However, comparing results among studies in which different tasks were used can be difficult, and it is unclear which task may be most appropriate. OBJECTIVE   To compare lower extremity biomechanics across 5 commonly used landing tasks. DESIGN   Descriptive laboratory study. SETTING   University-operated US Air Force Special Operations Forces human performance research laboratory. PATIENTS OR OTHER PARTICIPANTS   A total of 65 US Air Force Special Tactics Operators (age = 27.7 ± 5.0 years, height = 176.5 ± 5.7 cm, mass = 83.1 ± 9.1 kg). INTERVENTION(S)   Kinematic and kinetic analysis of double- and single-legged drop landing, double- and single-legged stop jump, and forward jump to single-legged landing. MAIN OUTCOME MEASURE(S)   Hip-, knee-, and ankle-joint kinematics; knee-joint forces and moments; and ground reaction forces (GRFs) were the dependent measures. We used repeated-measures analyses of variance or Friedman tests, as appropriate, to assess within-subject differences across tasks. RESULTS   Peak vertical GRF and peak knee-flexion angle were different among all tasks ( P < .001). Single-legged landings generated higher vertical GRF (χ2 = 244.68, P < .001) and lower peak knee-flexion values ( F4,64 = 209.33, P < .001) except for forward jump to single-legged landing, which had the second highest peak vertical GRF and the lowest peak knee-flexion value. The single-legged drop landing generated the highest vertical (χ2 = 244.68, P < .001) and posterior (χ2 = 164.46, P < .001) GRFs. Peak knee-valgus moment was higher during the double-legged drop landing (χ2 = 239.63, P < .001) but similar for all others. CONCLUSIONS   Different landing tasks elicited different biomechanical responses; no single task was best for assessing a wide range of biomechanical variables related to anterior cruciate ligament injuries. Therefore, depending on the goals of the study, using multiple assessment tasks should be considered.

Normative Data for the NeuroCom Sensory Organization Test in US Military Special Operations Forces

CONTEXT Postural stability is the ability to control the center of mass in relation to a persons base of support and can be affected by both musculoskeletal injury and traumatic brain injury. The NeuroCom Sensory Organization Test (SOT) can be used to objectively quantify impairments to postural stability. The ability of postural stability to predict injury and be used as an acute injury-evaluation tool makes it essential to the screening and rehabilitation process. To our knowledge, no published normative data for the SOT from a healthy, highly active population are available for use as a reference for clinical decision making. OBJECTIVE To present a normative database of SOT scores from a US Military Special Operations population that can be used for future comparison. DESIGN Cross-sectional study. SETTING Human performance research laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 542 active military operators from Naval Special Warfare Combatant-Craft Crewmen (n = 149), Naval Special Warfare Command, Sea, Air, and Land (n = 101), US Army Special Operations Command (n = 171), and Air Force Special Operations Command (n = 121). MAIN OUTCOME MEASURE(S) Participants performed each of the 6 SOT conditions 3 times. Scores for each condition, total equilibrium composite score, and ratio scores for the somatosensory, visual, and vestibular systems were recorded. RESULTS Differences were present across all groups for SOT conditions 1 (P < .001), 2 (P = .001), 4 (P > .001), 5 (P > .001), and 6 (P = .001) and total equilibrium composite (P = .000), visual (P > .001), vestibular (P = .002), and preference (P > .001) NeuroCom scores. CONCLUSIONS Statistical differences were evident in the distribution of postural stability across US Special Operations Forces personnel. This normative database for postural stability, as assessed by the NeuroCom SOT, can provide context when clinicians assess a Special Operations Forces population or any other groups that maintain a high level of conditioning and training.

Relationship of performance on the sensory organization test to landing characteristics

ABSTRACT Jump landing tasks have been used to assess landing characteristics and require significant sensorimotor feedback to maintain functional joint stability (FJS) throughout the task. Postural stability (PS) also requires significant sensorimotor feedback and control and would seemingly involve similar sensory feedback pathways. However, previous literature clarifying the relationship between these two processes, maintaining FJS and PS, is limited. 80 Special Tactics Operators. PS was assessed using the Sensory Organization Test (SOT). SOT variables included: Composite, Somatosensory, Visual, Vestibular, and Preference scores. Landing characteristics were assessed using motion analysis during a double-legged (DLSJ) and single-legged (SLSJ) stop jump task. Pearson’s correlation coefficients were calculated to assess the relationship between SOT scores and landing characteristics (α < .05). For the DLSJ, significant correlations were found between: Composite and peak posterior ground reaction forces (−.257), Vestibular and peak knee abduction moment (−.237), and Preference and initial contact hip flexion (−.297), peak hip flexion (−.249). For the SLSJ, significant correlations were found between: Somatosensory and peak vertical ground reaction forces (−.246); Preference and initial contact hip flexion (−.295), peak hip flexion (−.262). The results indicate that the SOT may not be a sensitive enough tool to assess sensorimotor control in a healthy, athletic population.

Energy expenditure and intake during Special Operations Forces field training in a jungle and glacial environment

The purpose of this study was to identify and compare energy requirements specific to Special Operations Forces in field training, in both cool and hot environments. Three separate training sessions were evaluated, 2 in a hot environment (n = 21) and 1 in a cool environment (n = 8). Total energy expenditure was calculated using doubly labeled water. Dietary intake was assessed via self-report at the end of each training mission day, and macronutrient intakes were calculated. Across the 3 missions, mean energy expenditure (4618 ± 1350 kcal/day) exceeded mean energy intake (2429 ± 838 kcal/day) by an average of 2200 kcal/day. Macronutrient intakes (carbohydrates (g/(kg·day body weight (bw))-1) = 3.2 ± 1.2; protein (g/(kg·day bw)-1) = 1.3 ± 0.7; fat (g/(kg·day bw)-1) = 1.2 ± 0.7) showed inadequate carbohydrate and possibly protein intake across the study period, compared with common recommendations. Total energy expenditures were found to be similar between hot (4664 ± 1399 kcal/day) and cool (4549 ± 1221 kcal/day) environments. However, energy intake was found to be higher in the cool (3001 ± 900 kcal/day) compared with hot (2200 ± 711 kcal/day) environments. Based on the identified energy deficit, high variation in energy expenditures, and poor macronutrient intake, a greater attention to feeding practices during similar training scenarios for Special Operations Forces is needed to help maintain performance and health. The differences in environmental heat stress between the 2 climates/environments had no observed effect on energy expenditures, but may have influenced intakes.

Greater ankle strength, anaerobic and aerobic capacity, and agility predict Ground Combat Military Occupational School graduation in female Marines

Women can serve in all military occupational specialties (MOS); however, musculoskeletal and physiological characteristics that predict successful completion of ground combat MOS schools by female Marines are unknown. OBJECTIVES To determine which demographic, musculoskeletal, and physiological characteristics predict graduation from infantry and vehicle ground combat MOS schools in female Marines. DESIGN Prospective cohort study. METHODS Prior to MOS school, the following were assessed in 62 female Marines (22.0±3.0yrs, 163.9±5.8cm, 63.4±7.2kg): isokinetic shoulder, trunk, and knee and isometric ankle strength; body composition; anaerobic power (AP)/capacity (AC); maximal oxygen uptake (VO2max); and field-based fitness tests (broad jump, medicine ball throw, pro-agility). Both absolute and normalized (%body mass: %BM) values were utilized for strength, AP, AC, and VO2max. Select tests from each Marines most recent Physical Fitness Test (PFT: abdominal crunches, 3-mile run time) and Combat Fitness Test (CFT: Maneuver Under Fire, Movement to Contact) were recorded. Participants were classified as graduated (N=46) or did not graduate (N=16). Simple logistic regression was performed to determine predictors of MOS school graduation. Statistical significance was set a priori at α=0.05. RESULTS Absolute and normalized ankle inversion and eversion strength, normalized anaerobic capacity, absolute and normalized VO2max, right pro-agility, and PFT 3-mile run time significantly predicted MOS school graduation (p<0.05). CONCLUSIONS Greater ankle strength, better agility, and greater anaerobic and aerobic capacity are important for successful completion of ground combat MOS school in female Marines. Prior to entering ground combat MOS school, it is recommended that female Marines should train to optimize these mobility-centric characteristics.

Association of prospective lower extremity musculoskeletal injury and musculoskeletal, balance, and physiological characteristics in Special Operations Forces

OBJECTIVES Previous research has examined lower extremity (LE) musculoskeletal injury (MSI) patterns and risk factors in Special Operations Forces (SOF) trainees, conventional military personnel, and athletes; however, it is unclear if SOF have the same patterns/risk factors. This study aimed to determine the association of musculoskeletal, balance, and physiological characteristics with LE MSI in SOF. DESIGN Cohort study. METHODS A total of 726 Air Force (N=140), Navy Sea, Air, and Land (N=301), and Special Warfare Combatant Crewmen (N=285) SOF (age=25.72±4.77years, height=178.34±6.63cm, weight=84.28±9.03kg) participated in laboratory testing, including: LE muscular strength and flexibility; balance; body composition; anaerobic power/capacity; and aerobic capacity. Medical charts were reviewed for LE MSI 365days following laboratory testing. Participants were assigned by injury status and laboratory data stratified by tertile. Chi-square statistics were calculated to determine the frequency of LE MSI across tertiles for each characteristic. RESULTS There was a significant association between LE MSI and: ankle inversion strength (weaker side: Χ(2)=17.703; stronger side: Χ(2)=18.911; p≤0.001); ankle eversion/inversion strength ratio (lower side: Χ(2)=13.456; higher side: Χ(2)=16.885; p≤0.001); hamstring flexibility (less flexible: Χ(2)=19.930; more flexible Χ(2)=15.185; p≤0.001); gastrocnemius-soleus flexibility (less flexible: Χ(2)=7.889, p=0.019); dynamic balance asymmetry (Χ(2)=7.444, p=0.024); Vestibular and Preference ratios (Χ(2)=9.124, p=0.010 and Χ(2)=6.572, p=0.037, respectively); and aerobic capacity (Χ(2)=13.935, p=0.001). CONCLUSIONS Characteristics associated with LE MSI are unique in SOF. Human performance program initiatives should include efforts to optimize ankle strength and flexibility, maintain moderate hamstring flexibility, expand dynamic balance strategies, and maximize aerobic capacity to reduce LE MSI risk.

Poor anaerobic power/capability and static balance predicted prospective musculoskeletal injuries among Soldiers of the 101st Airborne (Air Assault) Division

Musculoskeletal injuries have negatively impacted tactical readiness. The identification of prospective and modifiable risk factors of preventable musculoskeletal injuries can guide specific injury prevention strategies for Soldiers and health care providers. OBJECTIVES To analyze physiological and neuromuscular characteristics as predictors of preventable musculoskeletal injuries. DESIGN Prospective-cohort study. METHODS A total of 491 Soldiers were enrolled and participated in the baseline laboratory testing, including body composition, aerobic capacity, anaerobic power/capacity, muscular strength, flexibility, static balance, and landing biomechanics. After reviewing their medical charts, 275 male Soldiers who met the criteria were divided into two groups: with injuries (INJ) and no injuries (NOI). Simple and multiple logistic regression analyses were used to calculate the odds ratio (OR) and significant predictors of musculoskeletal injuries (p<0.05). RESULTS The final multiple logistic regression model included the static balance with eyes-closed and peak anaerobic power as predictors of future injuries (p<0.001). CONCLUSIONS The current results highlighted the importance of anaerobic power/capacity and static balance. High intensity training and balance exercise should be incorporated in their physical training as countermeasures.

Injury Epidemiology of Unintentional Musculoskeletal Injuries in United States Air Force Special Tactics Forces: 3346 Board #107 May 30, 9

A first step in the injury prevention process is determining the magnitude and scope of unintentional musculoskeletal injuries (MSIs) in the target population. US Air Force Special Tactics (ST) are a distinct group of Special Operations Forces Operators who maintain a high level of tactical readiness for their unique mission set. PURPOSE: To describe the injury epidemiology, including type, location, and activity when injury occurred, of ST utilizing a guided self-reported injury questionnaire. METHODS: A total of 95 ST Operators were enrolled (Age: 27.8 ± 5.4 years, Height: 177.3 ± 6.1 cm, Mass: 82.6 ± 8.6 kg) in the study. Self-reported injury history was collected by a certified athletic trainer for a one-year period. A MSI was defined as an injury to the musculoskeletal system that resulted in alteration of tactical activities, tactical training, or physical training for a minimum of one day, regardless if medical attention was sought. Injury data was categorized based on injury type, activity, mechanism of injury across all and preventable injuries (PIs). PIs were defined as an unintentional injury that may be reduced through injury prevention programs. Incidence, frequency, anatomical location, and activity were described for all injuries and injuries classified as preventable. RESULTS: The frequency of total injuries (TIs) was 33.7 MSIs while PIs was 15.8 MSIs/100 Operators/year. The incidence of TIs was 24.2 MSIs while PIs was 12.6 injured Operators/100 Operators/year. The upper extremity was the most commonly injured anatomic location followed by the spine and lower extremity for both TIs and PIs. Physical training was the most reported activity for TIs and PIs with 76.5% of TIs reported during PT as preventable. CONCLUSION: The current epidemiology data demonstrates that 46.9% of MSIs are preventable. AFSOC has recently integrated a human performance team across their squadrons in order to counter the risk of injury and to optimize performance. The results of the current study should guide the human performance team’s effort to mitigate MSIs and extend the career longevity and quality of life of the ST Operator.