Lessons From Special Forces Operators for Elite Team Sports Training: How to Make the Whole Greater Than the Sum of the Parts.

This methodology paper describes the design of a holistic and multidisciplinary human performance program within the Belgian Special Forces Group, the Tier 1 Special Operations unit of the Belgian Defense. Performance management approaches in the military draw heavily on sports science. The key component of the program design described here is its integrative nature, which team sports training might benefit from. The basic rationale behind the program was to bridge several gaps: the gap between physical and mental training; the gap between the curative or preventive medical approach and the performance enhancement approach; and the gap between individual and team training. To achieve this goal, the methodology of Intervention Mapping was applied, and a multidisciplinary team of training and care professionals was constituted with operational stakeholders. This was the first step in the program design. The second step took a year, and consisted of formal and informal consultations, participant observations and task analyses. These two first stages and their conclusions are described in the Method section. The Results section covers the next two stages (three and four) of the process, which aimed at defining the content of the program; and to test a pilot project implementation. The third stage encompassed the choice of the most relevant assessment and intervention tools for the target population, within each area of expertise. This is described extensively, to allow for replication. The fourth and last stage was to "test drive" the real-life integration and implementation of the whole program at the scale of a single team (8 individuals). For obvious confidentiality reasons, the content data will not be reported extensively here. Implications for wider-scale implementation and tie-back to sports team training are presented.

Measuring Spatiotemporal Parameters on Treadmill Walking Using Wearable Inertial System.

This study aims to measure and compare spatiotemporal gait parameters in nineteen subjects using a full wearable inertial mocap system Xsens (MVN Awinda, Netherlands) and a photoelectronic system one-meter OptoGaitTM (Microgait, Italy) on a treadmill imposing a walking speed of 5 km/h. A total of eleven steps were considered for each subject constituting a dataset of 209 samples from which spatiotemporal parameters (SPT) were calculated. The step length measurement was determined using two methods. The first one considers the calculation of step length based on the inverted pendulum model, while the second considers an anthropometric approach that correlates the stature with an anthropometric coefficient. Although the absolute agreement and consistency were found for the calculation of the stance phase, cadence and gait cycle, from our study, differences in SPT were found between the two systems. Mean square error (MSE) calculation of their speed (m/s) with respect to the imposed speed on a treadmill reveals a smaller error (MSE = 0.0008) using the OptoGaitTM. Overall, our results indicate that the accurate detection of heel strike and toe-off have an influence on phases and sub-phases for the entire acquisition. Future study in this domain should investigate how to design and integrate better products and algorithms aiming to solve the problematic issues already identified in this study without limiting the user's need and performance in a different environment.

Energy Balance and Energy Availability During a Selection Course for Belgian Paratroopers.

INTRODUCTION: Adequate energy supply is a prerequisite for optimal performances and recovery. The aims of the present study were to estimate energy balance and energy availability during a selection course for Belgian paratroopers. METHODS: Energy expenditure by physical activity was measured with accelerometer (ActiGraph GT3X+, ActiGraph LLC, Pensacola, FL, USA) and rest metabolic rate in Cal.d-1 with Tinsley et al.'s equation based on fat-free mass = 25.9 × fat-free mass in kg + 284. Participants had only access to the French individual combat rations of 3,600 Cal.d-1, and body fat mass was measured with quadripolar impedance (Omron BF508, Omron, Osaka, Japan). Energy availability was calculated by the formula: ([energy intake in foods and beverages] - [energy expenditure physical activity])/kg FFM-1.d-1, with FFM = fat-free mass. RESULTS: Mean (SD) age of the 35 participants was 25.1 (4.18) years, and mean (SD) percentage fat mass was 12.0% (3.82). Mean (SD) total energy expenditure, i.e., the sum of rest metabolic rate, dietary-induced thermogenesis, and physical activity, was 5,262 Cal.d-1 (621.2), with percentile 25 at 4,791 Cal.d-1 and percentile 75 at 5,647 Cal.d-1, a difference of 856 Cal.d-1. Mean daily energy intake was 3,600 Cal.d-1, giving a negative energy balance of 1,662 (621.2) Cal.d-1. Mean energy availability was 9.3 Cal.kg FFM-1.d-1. Eleven of the 35 participants performed with a negative energy balance of 2,000 Cal.d-1, and only five participants out of 35 participants performed at a less than 1,000 Cal.d-1 negative energy balance level. CONCLUSIONS: Energy intake is not optimal as indicated by the negative energy balance and the low energy availability, which means that the participants to this selection course had to perform in suboptimal conditions.

Study protocol: a single-blind, multi-center, randomized controlled trial comparing dynamic intraligamentary stabilization, internal brace ligament augmentation and reconstruction in individuals with an acute anterior cruciate ligament rupture: LIBRƎ study.

BACKGROUND: The current gold standard for the treatment of an anterior cruciate ligament (ACL) rupture is reconstruction with tendon graft. Recently, two surgical ACL repair techniques have been developed for treating an acute ACL rupture: Dynamic Intraligamentary Stabilization (DIS, Ligamys®) and Internal Brace Ligament Augmentation (IBLA, InternalBrace™). We will conduct a single-blind, multi-center, randomized controlled trial which compares DIS, IBLA and reconstruction for relative clinical efficacy and economic benefit. METHODS: Subjects, aged 18-50 years, with a proximal, primary and repairable ACL rupture will be included. DIS is preferably performed within 4 weeks post-rupture, IBLA within 12 weeks and reconstruction after 4 weeks post-rupture. Patients are included in study 1 if they present within 0-4 weeks post-rupture and surgery is feasible within 4 weeks post-rupture. Patients of study 1 will be randomized to either DIS or IBLA. Patients are included in study 2 if they present after 4 weeks post-rupture and surgery is feasible between 5 and 12 weeks post-rupture. Patients of study 2 will be randomized to either IBLA or reconstruction. A total of 96 patients will be included, with 48 patients per study and 24 patients per study arm. Patients will be followed-up for 2 years. The primary outcome is change from baseline (pre-rupture) in International Knee Documentation Committee score to 6 months post-operatively. The main secondary outcomes are the EQ-5D-5 L, Tegner score, Lysholm score, Lachman test, isokinetic and proprioceptive measurements, magnetic resonance imaging outcome, return to work and sports, and re-rupture/failure rates. The statistical analysis will be based on the intention-to-treat principle. The economic impact of the surgery techniques will be evaluated by the cost-utility analysis. The LIBRƎ study is to be conducted between 2018 and 2022. DISCUSSION: This LIBRƎ study protocol is the first study to compare DIS, IBLA and ACL reconstruction for relative clinical efficacy and economic benefit. The outcomes of this study will provide data which could aid orthopaedic surgeons to choose between the different treatment options for the surgical treatment of an acute ACL rupture. TRIAL REGISTRATION: This study is registered at ClinicalTrials.gov; NCT03441295. Date registered 13.02.2018.

Decreased Average Power of the Hip External Muscles as a Predictive Parameter for Lower Extremity Injury in Women: A Prospective Study.

OBJECTIVE: To prospectively identify hip strength associated risk factors contributing to the development of lower extremity (LE) injury. DESIGN: Data were prospectively collected on healthy female physical education students. SETTING: This study was conducted in the institution of the University of Ghent. PARTICIPANTS: Eighty-nine female physical education students aged 19.53 ± 1.07 years. ASSESSMENT OF RISK FACTORS: Testing included isokinetic hip strength measurements of abductors, adductors, internal rotators, and external rotators (ERs). MAIN OUTCOME MEASURES: Follow-up of the participants was assessed using a weekly online questionnaire and a 3-month retrospective control questionnaire. Lower extremity injury was diagnosed by an experienced medical doctor. Cox regression was used to identify the potential risk factors for the development of an LE injury. RESULTS: Thirty-four participants were diagnosed with an LE injury during follow-up. This study identified that decreased average power (AP) (P = 0.031) on concentric ER strength was found to be a significant risk factor for LE injury. No other hip strength parameters were found to be significant contributors to the development of LE injury. CONCLUSIONS: Decreased AP of the hip ER muscles was identified as a significant predictor for LE injury, whereas no hip abduction weakness or peak torque parameters were found to be predictive. Because controlling LE extremity movements is an important function of the hip muscles, they might be more challenged in a dynamic measure such as AP than in a point measure such as peak torque. Concentric AP of hip ER muscles can therefore be seen as an interesting factor to include in LE injury screening protocols.

Cervical Joint Position Sense in Hypobaric Conditions: A Randomized Double-Blind Controlled Trial.

Well-adapted motor actions require intact and well-integrated information from all of the sensory systems, specifically the visual, vestibular, and somatosensory systems, including proprioception. Proprioception is involved in the sensorimotor control by providing the central nervous system with an updated body schema of the biomechanical and spatial properties of the body parts. With regard to the cervical spine, proprioceptive information from joint and muscle mechanoreceptors is integrated with vestibular and visual feedback to control head position, head orientation, and whole body posture. Postural control is highly complex and proprioception from joints is an important contributor to the system. Altitude has been used as a paradigm to study the mechanisms of postural control. Determining the mechanisms of postural control that are affected by moderate altitude is important as unpressurized aircrafts routinely operate at altitudes where hypoxia may be a concern. Deficits in motor performance arise when the reliance on proprioceptive feedback is abolished either experimentally or because of a disorder. As pilots require good neck motor control to counteract the weight of their head gear and proprioceptive information plays an important role in this process, the aim of this study was to determine if hypoxia at moderate altitudes would impair proprioception measured by joint position sense of the cervical spine in healthy subjects. METHODS: Thirty-six healthy subjects (Neck Disability Index < 5) volunteered to participate. Neck position sense was evaluated using a three-dimensional motion analyzer. To create the environment, a hypobaric chamber was used to simulate artificial moderate altitude. Head repositioning error was measured by asking the subject to perform a head-to-neutral task after submaximal flexion-extension and right/left rotation movements, and a head-to-target task, in which the subjects had to return to a 30° right and left rotation position. FINDINGS: Exposure to artificial acute moderate altitude of 7,000 feet had no significant effects on cervical joint position sense measured by head repositioning accuracy in healthy subjects. Discussion/impact/recommendations: Postural control mechanisms are very sensitive to acute mild hypoxia and have been recently investigated. Acute hypobaric hypoxia at moderate and high altitudes has a negative effect on postural control. However, which part of the postural system is affected has not yet been determined and proprioception has been little investigated. The results from this study highlighted that in healthy subjects with good cervical spine proprioception at baseline, artificial hypoxia induced by the simulation of moderate altitude does not increase head repositioning error. Further studies should investigate cervical joint position sense in real aircraft, at different altitudes and in a group of experienced helicopter pilots, to evaluate the impact of moderate altitude on cervical joint position sense in a different population. Conducting the same experiments in a population of pilots and in real flight conditions should be considered, since various factors such as the level of proprioception, head posture, type of movement, head load, muscle fatigue, flight altitude, and the length of flight time might influence the kinesthetic sensitivity.

Deviating running kinematics and hamstring injury susceptibility in male soccer players: Cause or consequence?

BACKGROUND: Although the vast majority of hamstring injuries in male soccer are sustained during high speed running, the association between sprinting kinematics and hamstring injury vulnerability has never been investigated prospectively in a cohort at risk. PURPOSE: This study aimed to objectify the importance of lower limb and trunk kinematics during full sprint in hamstring injury susceptibility. STUDY DESIGN: Cohort study; level of evidence, 2. METHODS: At the end of the 2013 soccer season, three-dimensional kinematic data of the lower limb and trunk were collected during sprinting in a cohort consisting of 30 soccer players with a recent history of hamstring injury and 30 matched controls. Subsequently, a 1.5 season follow up was conducted for (re)injury registry. Ultimately, joint and segment motion patterns were submitted to retro- and prospective statistical curve analyses for injury risk prediction. RESULTS: Statistical analysis revealed that index injury occurrence was associated with higher levels of anterior pelvic tilting and thoracic side bending throughout the airborne (swing) phases of sprinting, whereas no kinematic differences during running were found when comparing players with a recent hamstring injury history with their matched controls. CONCLUSION: Deficient core stability, enabling excessive pelvis and trunk motion during swing, probably increases the primary injury risk. Although sprinting encompasses a relative risk of hamstring muscle failure in every athlete, running coordination demonstrated to be essential in hamstring injury prevention.

Prone Hip Extension Muscle Recruitment is Associated with Hamstring Injury Risk in Amateur Soccer.

'Core stability' is considered essential in rehabilitation and prevention. Particularly with respect to hamstring injury prevention, assessment and training of lumbo-pelvic control is thought to be key. However, supporting scientific evidence is lacking. To explore the importance of proximal neuromuscular function with regard to hamstring injury susceptibility, this study investigated the association between the Prone Hip Extension (PHE) muscle activation pattern and hamstring injury incidence in amateur soccer players. 60 healthy male soccer players underwent a comprehensive clinical examination, comprising a range of motion assessments and the investigation of the posterior chain muscle activation pattern during PHE. Subsequently, hamstring injury incidence was recorded prospectively throughout a 1.5-season monitoring period. Players who were injured presented a PHE activation pattern that differed significantly from those who did not. Contrary to the controls, hamstring activity onset was significantly delayed (p=0.018), resulting in a shifted activation sequence. Players were 8 times more likely to get injured if the hamstring muscles were activated after the lumbar erector spinae instead of vice versa (p=0.009). Assessment of muscle recruitment during PHE demonstrated to be useful in injury prediction, suggesting that neuromuscular coordination in the posterior chain influences hamstring injury vulnerability.

Proximal Neuromuscular Control Protects Against Hamstring Injuries in Male Soccer Players: A Prospective Study With Electromyography Time-Series Analysis During Maximal Sprinting.

BACKGROUND: With their unremittingly high incidence rate and detrimental functional repercussions, hamstring injuries remain a substantial problem in male soccer. Proximal neuromuscular control ("core stability") is considered to be of key importance in primary and secondary hamstring injury prevention, although scientific evidence and insights on the exact nature of the core-hamstring association are nonexistent at present. HYPOTHESIS: The muscle activation pattern throughout the running cycle would not differ between participants based on injury occurrence during follow-up. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Sixty amateur soccer players participated in a multimuscle surface electromyography (sEMG) assessment during maximal acceleration to full-speed sprinting. Subsequently, hamstring injury occurrence was registered during a 1.5-season follow-up period. Hamstring, gluteal, and trunk muscle activity time series during the airborne and stance phases of acceleration were evaluated and statistically explored for a possible causal association with injury occurrence and absence from sport during follow-up. RESULTS: Players who did not experience a hamstring injury during follow-up had significantly higher amounts of gluteal muscle activity during the front swing phase ( P = .027) and higher amounts of trunk muscle activity during the backswing phase of sprinting ( P = .042). In particular, the risk of sustaining a hamstring injury during follow-up lowered by 20% and 6%, with a 10% increment in normalized muscle activity of the gluteus maximus during the front swing and the trunk muscles during the backswing, respectively ( P < .024). CONCLUSION: Muscle activity of the core unit during explosive running appeared to be associated with hamstring injury occurrence in male soccer players. Higher amounts of gluteal and trunk muscle activity during the airborne phases of sprinting were associated with a lower risk of hamstring injuries during follow-up. Hence, the present results provide a basis for improved, evidence-based rehabilitation and prevention, particularly focusing on increasing neuromuscular control of the gluteal and trunk muscles during sport-specific activities (eg, sprint drills, agility drills).

Susceptibility to Hamstring Injuries in Soccer: A Prospective Study Using Muscle Functional Magnetic Resonance Imaging.

BACKGROUND: Running-related hamstring strain injuries remain a delicate issue in several sports such as soccer. Their unremittingly high incidence and recurrence rates indicate that the underlying risk has not yet been fully identified. Among other factors, the importance of neuromuscular coordination and the quality of interplay between the different hamstring muscle bellies is thought to be a key determinant within the intrinsic injury risk. Muscle functional magnetic resonance imaging (mfMRI) is one of the tools that has been proven to be valid for evaluating intermuscular coordination. PURPOSE: To investigate the risk of sustaining an index or recurring soccer-related hamstring injury by exploring metabolic muscle characteristics using mfMRI. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 27 healthy male soccer players and 27 soccer players with a history of hamstring injuries underwent standardized mfMRI. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise, and a postexercise scan. The exercise-related T2 change, or the signal intensity shift between both scans, was used to detect differences in metabolic characteristics between (1) the different hamstring muscle bellies and (2) the prospective cohorts based on the (re)occurrence of hamstring injuries during a follow-up period of 18 months. RESULTS: The risk of sustaining a first hamstring injury was associated with alterations in the intermuscular hierarchy in terms of the magnitude of the metabolic response after a heavy eccentric effort, with the dominant role of the semitendinosus set aside for a higher contribution of the biceps femoris (P = .017). Receiver operating characteristic (ROC) curve analysis demonstrated that this variable was significantly able to predict the occurrence of index injuries with a sensitivity of 100% and a specificity of 70% when the metabolic activity of the biceps femoris exceeded 10%. The risk of sustaining a reinjury was associated with a substantial deficit in hamstring strength endurance (P = .031). Soccer players who sustained a reinjury were only able to perform prone leg curls for a mean duration of 146.50 ± 76.16 seconds, whereas those with an injury history but no recurrence during follow-up were able to continue for a mean of 237.45 ± 110.76 seconds (95% CI, 11.9-230.5 seconds; P = .031). CONCLUSION: This was the first study to assess the causal relation between the intramuscular recruitment pattern and the risk of sustaining an index or secondary hamstring strain. Changes in intermuscular interplay seem to significantly increase the risk of sustaining index hamstring injuries in male amateur soccer players. Inadequate eccentric muscle endurance could be associated with an increased risk of sustaining a recurring hamstring injury.

Biceps femoris and semitendinosus--teammates or competitors? New insights into hamstring injury mechanisms in male football players: a muscle functional MRI study.

BACKGROUND: The hamstring injury mechanism was assessed by investigating the exercise-related metabolic activity characteristics of the hamstring muscles using a muscle functional MRI (mfMRI) protocol. METHODS: 27 healthy male football players and 27 football players with a history of hamstring injuries (recovered and playing fully) underwent standardised mfMR Imaging. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise and a postexercise scan. The exercise-related T2 increase or the signal intensity shift between both scans was used to detect differences in metabolic activation characteristics (1) between the different hamstring muscle bellies and (2) between the injury group and the control group. RESULTS: A more symmetrical muscle recruitment pattern corresponding to a less economic hamstring muscle activation was demonstrated in the formerly injured group (p<0.05). The injured group also demonstrated a significantly lower strength endurance capacity during the eccentric hamstring exercise. CONCLUSIONS: These findings suggest that the vulnerability of the hamstring muscles to football-related injury is related to the complexity and close coherence in the synergistic muscle recruitment of the biceps femoris and the semitendinosus. Discrete differences in neuromuscular coordination and activity distribution, with the biceps femoris partly having to compensate for the lack of endurance capacity of the semitendinosus, probably increase the hamstring injury risk.

A surface electromyography based objective method to identify patients with nonspecific chronic low back pain, presenting a flexion related movement control impairment.

Movement control impairments (MCI) are often present in patients with non-specific chronic low back pain (NS-CLBP). Therefore, movement control exercises are widely used to rehabilitate patients. However, the objective assessment remains difficult. The purpose of this study was to develop a statistical model, based on logistic regression analysis, to differentiate patients with NS-CLBP presenting a flexion-related MCI from healthy subjects. This model is based on trunk muscle activation patterns measured by surface electromyography (sEMG), during movement control exercises. Sixty-three healthy male subjects and 36 male patients with a flexion-related MCI participated in this study. Muscle activity of the internal obliques, the external obliques, the lumbar multifidus and the thoracic part of the iliocostalis was registered. Ratios of deep stabilizing to superficial torque producing muscle activity were calculated to examine trunk muscle recruitment patterns during 6 different exercises. Logistic regression analyses were performed (1) to define the ratios and exercises that were most discriminating between patients and non-patients, (2) to make a predictive model. K-Fold cross-validation was used to assess the performance of the predictive model. This study demonstrated that sEMG trunk muscle recruitment patterns during movement control tests, allows differentiating NSCLBP patients with a flexion-related MCI from healthy subjects.

Performance based on sEMG activity is related to psychosocial components: differences between back and abdominal endurance tests.

The influence of psychosocial components on back and abdominal endurance tests in patients with persistent non-specific low back pain should be investigated to ensure the correct interpretation of these measures. Three-hundred and thirty-two patients (291 men and 41 women) from 19 to 63years performed an abdominal and back muscle endurance test after completing some psychosocial questionnaires. During the endurance tests, surface electromyography signals of the internal obliques, the external obliques, the lumbar multifidus and the iliocostalis were recorded. Patients were dichotomized as underperformers and good performers, by comparing their real endurance time, to the expected time of endurance derived from the normalized median frequency slope. Independent t-tests were performed to examine the differences on the outcome of the questionnaires. In the back muscle endurance test, the underperformers had significantly lower (p<0.05) scores on some of the physical subscales of the SF-36. The underperformers group of the AE test scored significantly higher on the DRAM MZDI (p=0.018) and on the PCS scale (p=0.020) and showed also significantly lower scores on the SF-36 (p<0.05). Back muscle endurance tests are influenced by physical components, while abdominal endurance tests seem influenced by psychosocial components.

Muscle functional MRI to evaluate quadriceps dysfunction in patellofemoral pain.

PURPOSE: A dysfunction of the quadriceps muscle group has often been suggested to play an important role in the pathophysiology of patellofemoral pain (PFP). However, consensus is lacking regarding the quadriceps recruitment pattern of patients with PFP. The aim of this study was to examine by muscle functional magnetic resonance imaging if patients with PFP actually exhibit an altered activation of the muscles that play a significant role in the dynamic balance of the patella. METHODS: Forty-six patients with PFP (25 female and 21 male, mean ± SD age = 25.0 ± 7.4 yr) and 30 healthy control subjects (17 female and 13 male, mean ± SD age = 21.6 ± 4.5 yr) underwent MRI of the quadriceps before and immediately after a squat exercise. The transverse relaxation time (T2) and the T2 shift were calculated for the vasti muscles. RESULTS: There were no significant differences in the T2 values at rest and the T2 shift values between the patient and the control groups, except for the T2 rest value of the VMVI of females (P = 0.007). The T2 shift of the VL was significantly smaller than the T2 shift of the VMVI in both study groups (male P < 0.001 and female P = 0.044), while in females, the T2 shift of the VMO was also significantly smaller than the T2 shift of the VMVI (P = 0.027). CONCLUSIONS: The activation pattern of the quadriceps is not altered in patients with PFP for both males and females. Because the relative contribution of the quadriceps muscles to a functional activity has not been modified, there is no evidence for quadriceps dysfunction.

Velocity of isokinetic trunk exercises influences back muscle recruitment patterns in healthy subjects.

Isokinetic exercises at different angular velocities on Cybex devices are often used for assessment and therapy in chronic low back pain patients. Little is known about the effect of velocity of movement on the muscle activity during these exercises. The purpose of this study was to investigate both relative muscle activity and ratios of local to global muscle activity at the different velocities of isokinetic movements on a Cybex dynamometer. Fifty-three healthy employees of Belgian Defence (26 male and 27 female) aged between 20 and 57 years old voluntarily performed isometric and isokinetic exercises at four different velocities. Surface electromyographic signals of different abdominal and back muscles were recorded on both sides. Both the relative muscle activity and the local to global muscle activity ratio of the back muscles were affected by changes in velocities of isokinetic exercises. The global muscle system was more influenced by changes in velocity, than the local muscle system. Abdominal relative muscle activity and ratios were not influenced by velocity of movement. This study revealed that the velocity of isokinetic extension exercises influences the recruitment of the back muscles, meaning that protocols of training programs should be adapted in function of the focus of the therapy.

Is hip muscle weakness a predisposing factor for patellofemoral pain in female novice runners? A prospective study.

BACKGROUND: Hip muscle weakness has been proposed to contribute to patellofemoral malalignment and the development of the patellofemoral dysfunction syndrome (PFDS). However, from the retrospective studies that have addressed this issue, it is still unclear if hip muscle weakness is a cause or a consequence of PFDS. PURPOSE: This study was undertaken to investigate if hip muscle weakness is a predisposing factor for the development of PFDS. STUDY DESIGN: Cohort study (prognosis); Level of evidence, 2. METHODS: Before the start of a 10-week "start to run" program, the isometric strength of the hip flexor, extensor, abductor, adductor, and external and internal rotator muscles was measured in 77 healthy female novice runners. During the 10-week training period, patellofemoral pain was diagnosed and registered by an orthopaedic surgeon. RESULTS: Statistical analysis revealed that there was no significant difference in strength of any of the assessed hip muscle groups between the runners who did and did not develop PFDS. Logistic regression analysis did not identify a deviation in strength of any of the assessed hip muscle groups as a risk factor for PFDS. CONCLUSION: The findings of this study suggest that isometric hip muscle strength might not be a predisposing factor for the development of PFDS.

MRI study of the morphometry of the cervical musculature in F-16 pilots.

INTRODUCTION: In fighter pilots neck muscle strengthening exercises are often recommended to protect the neck against pathologies. The aim of the current study was to compare the relative cross-sectional area (rCSA) and muscle:fat ratio of the cervical musculature of F-16 pilots experiencing neck pain and no neck pain (control) pilots. In addition, correlations between these morphometric characteristics, cervical range of motion (CROM), and neck muscle strength were evaluated. METHODS: There were 35 male F-16 pilots who volunteered, of which 10 experienced bilateral neck pain. A standardized questionnaire was used to collect personal information. Magnetic resonance imaging (MRI) was assessed at the C5-C6 level to determine rCSA and muscle:fat ratio. The CROM (Zebris) and the maximum isometric strength (David F140 device) were measured. RESULTS: The rCSA of the semispinalis cervicis and multifidus was significantly larger in the neck pain group (left: 2.08 cm2; right: 1.81 cm2) on both the left and the right side, in comparison to the control population (left: 1.29 cm2; right: 1.26 cm2). In the pain group, the rCSA of the semispinalis cervicis and multifidus was significant larger on the left than on the right side (left: 2.08 cm2; right: 1.81 cm2). No differences in the muscle:fat ratio between control pilots and pilots with neck pain could be determined. Between groups no differences were found in the CROM and the neck muscle strength. DISCUSSION: It is hypothesized that the larger rCSA in the neck pain group compared to the control group might be caused by greater activity of the deep neck muscles in the neck pain group. The asymmetrical operation of the F-16 might cause the asymmetry within this group.

Functional assessment of the cervical spine in F-16 pilots with and without neck pain.

INTRODUCTION: Spinal symptoms in fighter pilots are a serious aeromedical problem. The most common neck complaints are muscular pain and strain. The aim of the current study was to determine possible differences in the cervical range of motion (CROM), neck position sense, and neck muscle strength between pilots with and without neck pain. METHODS: There were 90 male F-16 pilots who volunteered, of which 17 had experienced bilateral neck pain. A standardized questionnaire was used to collect personal information. The maximum isometric neck flexion/extension and lateral flexion strength, the neck position sense, and the cervical range of motion were measured. RESULTS: There were no significant differences between healthy pilots and those with neck pain concerning neck muscle strength and neck position sense. The neck pain group had a limited CROM in the sagittal plane (130 degrees; CI: 116 degrees-144 degrees) and in the transversal plane (155 degrees; CI: 140 degrees-170 degrees) compared to the healthy pilots. DISCUSSION: In the current study we screened for different motor skills so that deficits could be detected and retraining programs could be implemented when necessary. According to our results, individual retraining programs might reduce neck pain and therefore a well-instructed training program to maintain a proper active CROM should be implemented. Future studies should investigate the effectiveness of this kind of program.

Delayed vastus medialis obliquus to vastus lateralis onset timing contributes to the development of patellofemoral pain in previously healthy men: a prospective study.

BACKGROUND: Delayed onset of vastus medialis obliquus activity has been described in patellofemoral pain patients. No prospective study investigating the development of patellofemoral pain has tested the onset timing of electromyographic activity of the vastus medialis obliquus and vastus lateralis muscles during a functional task. HYPOTHESIS: Before the development of patellofemoral pain, subjects demonstrate an altered firing order of the vastus medialis obliquus and vastus lateralis muscles compared with healthy subjects during a functional task. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: The onset of vastus medialis obliquus and vastus lateralis activity was measured with surface electromyography during a functional task (rocking back on the heels) in 79 healthy subjects subsequently submitted to a 6-week strenuous basic military training. Afterward, these subjects were reassessed. RESULTS: Thirty-two percent of the recruits developed patellofemoral pain during training. Patellofemoral pain subjects demonstrated a significant delay of onset of vastus medialis obliquus electromyographic activity compared with the healthy controls (P = .023), even before basic military training. In healthy subjects, no significant differences in electromyographic activity onset of the vastus medialis obliquus compared with the vastus lateralis could be identified before and after basic military training. A significant (P < .001) delay could be demonstrated in the patellofemoral pain group after basic military training. A binary logistic regression could be constructed wherein the onset of the electromyographic activity of the vastus medialis obliquus and vastus lateralis was withheld in the model. The most optimal cutoff value, which is based on the receiver operating characteristic curve, is a timing difference of -0.67 milliseconds (vastus medialis obliquus - vastus lateralis). The area under the receiver operating characteristic curve is considered as fair (0.68). CONCLUSION: Delayed onset of electromyographic activity of the vastus medialis obliquus-vastus lateralis is one of the contributing risk factors to the development of patellofemoral pain.

Sock systems to prevent foot blisters and the impact on overuse injuries of the knee joint.

The incidence of foot blisters and other overuse injuries of the lower limb is very high during basic military training (BMT). One hundred and eighty-nine subjects were divided into two intervention groups wearing alternative sock systems and one control group. Overall, 57% of the 173 recruits who completed the training, developed foot blisters. Binary logistic regression revealed the type of sock, race, previous hiking or military experience, and known orthopedic foot conditions to be predictive variables for foot blisters. Fifty-three percent of the 173 recruits also developed another overuse injury of the lower limb (25.4% related to the knee joint). Previous military or hiking experience and the association of foot blisters revealed to be predictive for the overuse injuries of the knee joint. The results of the present study suggest associated foot blisters are also an important factor in the development of overuse injuries of the knee joint during BMT.