Tethered Swimming Test: Reliability and the Association With Swimming Performance and Land-Based Anaerobic Performance.

ABSTRACT: Nagle Zera, J, Nagle, EF, Nagai, T, Lovalekar, M, Abt, JP, and Lephart, SM. Tethered swimming test: reliability and the association with swimming performance and land-based anaerobic performance. J Strength Cond Res 35(1): 212-220, 2021-The purpose of this study was 3-fold: (a) to examine the test-retest reliability of a 30-second maximal tethered freestyle swimming test (TST), (b) to assess the validity of the TST by examining the association with sprint swimming performance, and (c) to examine the associations between a swim-specific and land-based measure of anaerobic performance. A total of 29 male and female swimmers were recruited to participate in the study. Each subject completed a Wingate Anaerobic cycling test (WAnT), 2 or 4 TST, and a 22.9 m (25 yd), 45.7 m (50 yd), and 91.4 m (100 yd) maximal freestyle performance swims (PS). Mean and peak force (Fmean and Fpeak) were recorded for both the WAnT and TST, and average swimming velocity and time were recorded for the PS. In addition, physiological and perceptual measures were recorded immediately postexercise for all tests. The results of the present investigation showed strong intersession and intrasession reliability (R = 0.821-0.975; p < 0.001) for force parameters of the TST. Moderate correlations were found between Fmean and PS time and velocity of all distances, with slightly weaker correlations between Fpeak and the 22.9 m (time and velocity) and 45.7 m (velocity) PS. Finally, moderate correlations were found for Fmean and Fpeak of the TST and WAnT. This study demonstrated that the TST is a reliable measure, with moderate association with swimming performance, producing similar physiological responses compared with free swimming. Therefore, future research should focus on investigating the potential benefits of using the TST as a regular assessment tool as a part of a competitive swimming training program to track adaptations and inform training decisions.

Altered Physical Performance Following Advanced Special Operations Tactical Training.

ABSTRACT: Winters, JD, Heebner, NR, Johnson, AK, Poploski, KM, Royer, SD, Nagai, T, Randall, CA, Abt, JP, and Lephart, SM. Altered physical performance following advanced special operations tactical training. J Strength Cond Res 35(7): 1809-1816, 2021-The purpose of this study was to determine how the unique challenges of specific military tactical training phases influence overall physical performance characteristics. Broad jump, 5-10-5, 300-yd shuttle, percent body fat (%BF), anaerobic power (AP) and anaerobic capacity (AC), maximal oxygen uptake (V̇o2max), isokinetic knee extension/flexion strength, shoulder internal/external rotation strength, and trunk extension/flexion strength were collected on 73 United States Marine Corps Forces Special Operations Command (MARSOC) students (age: 27.4 ± 3.8 years, height: 178.7 ± 6.6 cm, and body mass: 85.8 ± 9.4 kg) at the beginning of (P1), in between (P2), and at the completion of 2 distinct tactical training phases (P3). Linear mixed models were used to analyze within-subject performance changes over the 3 time points, and post hoc Bonferroni pairwise comparisons analyzed performance changes between each testing time point. There were significant changes in broad jump (p < 0.0001), 5-10-5 agility time (p < 0.001), %BF (p = 0.011), AP (p < 0.0001), V̇o2max (p = 0.001), and both right and left shoulder internal rotation strength (p = 0.004 and p = 0.015, respectively) between P1 and P2. There were also significant changes in 300-yd shuttle run time (p = 0.001), AP (p < 0.0001), AC (p < 0.0001), left knee extension strength (p = 0.006), trunk flexion strength (p < 0.0001), and left shoulder external rotation strength (0.027) between P2 and P3. Identifying the effect that specific tactical training phases may have on physical performance will allow for the development of effective phase-specific evidence-based human performance programs, reducing performance deficits and thereby reducing the risk of injury.

Reliability and Validity of a Pool-Based Maximal Oxygen Uptake Test to Examine High-Intensity Short-Duration Freestyle Swimming Performance.

Nagle, EF, Nagai, T, Beethe, AZ, Lovalekar, MT, Zera, JN, Connaboy, C, Abt, JP, Beals, K, Nindl, BC, Robertson, RJ, and Lephart, SM. Reliability and validity of a pool-based maximal oxygen uptake test to examine high-intensity short-duration freestyle swimming performance. J Strength Cond Res 33(5): 1208-1215, 2019-A modality-specific swimming protocol to assess maximal oxygen uptake (V[Combining Dot Above]O2maxsw) is essential to accurately prescribe and monitor swimming conditioning programs. Consequently, there is a need for a reliable and valid graded intensity swimming pool test to accurately assess V[Combining Dot Above]O2maxsw using indirect calorimetry. The purpose of this study was to assess (a) reliability of an intensity self-regulated swimming pool test of V[Combining Dot Above]O2maxsw and (b) validity of a V[Combining Dot Above]O2maxsw test using performance swim (PS) time as the criterion. Twenty-nine men (n = 15) and women (n = 14) (age, 23 ± 6.4 years; body mass index, 23.5 ± 3.0 kg·m) performed 2 swimming pool V[Combining Dot Above]O2maxsw trials (V[Combining Dot Above]O2maxsw A and V[Combining Dot Above]O2maxsw B), and 2 PS tests (45.7 m [31.20 ± 4.5 seconds] and 182 m [159.2 ± 25.5 seconds]). For test-retest reliability (trials A vs. B), strong correlations (p < 0.05) were found for V[Combining Dot Above]O2maxsw (ml·kg·min) (r = 0.899), O2 pulse (ml O2·beat) (r = 0.833), and maximum expired ventilatory volume (L·min) (r = 0.785). For performance validity, moderately strong correlations (p < 0.05) were found between V[Combining Dot Above]O2maxsw A and 45.7-m (r = -0.543) and 182-m (r = -0.486) swim times. The self-regulated graded intensity swimming pool protocol examined presently is a reliable and valid test of V[Combining Dot Above]O2maxsw. Studies should consider the suitability of a V[Combining Dot Above]O2maxsw test for military personnel, clinical populations, and injured athletes.

Gender Differences in Static and Dynamic Postural Stability of Soldiers in the Army's 101st Airborne Division (Air Assault).

CONTEXT: Postural stability is essential for injury prevention and performance. Differences between genders may affect training focus. OBJECTIVE: To examine static and dynamic postural stability in male and female soldiers. DESIGN: Descriptive laboratory study. SETTING: Biomechanics laboratory. PARTICIPANTS: 25 healthy female soldiers (26.4 ± 5.3 y) and 25 healthy male soldiers (26.4 ± 4.9 y) matched on physical demand rating and years of service from the Army's 101st Airborne Division (Air Assault). INTERVENTIONS: Each person underwent static and dynamic postural stability testing. MAIN OUTCOME MEASURES: Standard deviation of the ground reaction forces during static postural stability and the dynamic stability index for dynamic postural stability. RESULTS: Female soldiers had significantly better static postural stability than males but no differences were observed in dynamic postural stability. CONCLUSIONS: Postural stability is important for injury prevention, performance optimization, and tactical training. The differences observed in the current study may indicate the need for gender-specific training emphasis on postural stability.

Block-Periodized Training Improves Physiological and Tactically Relevant Performance in Naval Special Warfare Operators.

Human performance training and prevention strategies are necessary to promote physical readiness and mitigate musculoskeletal injuries of the Naval Special Warfare (NSW) Operator. The purpose of this study was to measure the effectiveness of 2 training programs when performed during a training evolution of Operators. A total of 85 Operators (experimental: n = 46, age: 29.4 ± 5.5 years, height: 176.7 ± 6.4 cm, mass: 86.7 ± 11.6 kg; control: n = 39, age: 29.0 ± 6.0 years, height: 177.1 ± 6.3 cm, mass: 85.7 ± 12.5 kg) participated in a trial to measure the effectiveness of these programs to improve physical, physiological, and performance characteristics. Operators in the experimental group performed a 12-week block-periodized program, whereas those in the control group performed a nonlinear periodized program. Pretesting/posttesting was performed to assess body composition, aerobic capacity/lactate threshold, muscular strength, flexibility, landing biomechanics, postural stability, and tactically relevant performance. The experimental group demonstrated a significant loss in body fat, fat mass, and body mass compared with the control group, whereas aerobic capacity increased for the both groups. The experimental group demonstrated a significant increase in posterior shoulder flexibility and ankle dorsiflexion, whereas the control group had a significant reduction in shoulder, knee, and ankle flexibility. The experimental group also improved landing strategies and balance. Both groups improved upper and lower muscular power and upper-body muscular endurance, whereas only the experimental group demonstrated significant improvements in agility and total body muscular strength. Implementation of a population-specific training program provides structured and progressive training effectively and promotes physical readiness concurrently with tactical training without overload.

Force Sense of the Knee Not Affected by Fatiguing the Knee Extensors and Flexors.

CONTEXT: Knee injuries commonly occur in later stages of competition, indicating that fatigue may influence dynamic knee stability. Force sense (FS) is a submodality of proprioception influenced by muscle mechanoreceptors, which, if negatively affected by fatigue, may result in less-effective neuromuscular control. OBJECTIVES: To determine the effects of peripheral fatigue on FS of the quadriceps and hamstrings. DESIGN: Quasi-experimental study design. PARTICIPANTS: 20 healthy and physically active women and men (age 23.4 ± 2.7 y, mass 69.5 ± 10.9 kg, height 169.7 ± 9.4 cm). INTERVENTIONS: Fatigue was induced during a protocol with 2 sets of 40 repetitions, and the last set was truncated at 90 repetitions or stopped if torque production dropped below 25% of peak torque. MAIN OUTCOME MEASURES: FS of the hamstrings and quadriceps was tested on separate days before and after 3 sets of isokinetic knee flexion and extension to fatigue by examining the ability to produce a target isometric torque (15% MVIC) with and without visual feedback (FS error). Electromyographic data of the tested musculature were collected to calculate and determine median frequency shift. T tests and Wilcoxon signed-rank tests were conducted to examine prefatigue and postfatigue FS error for flexion and extension. RESULTS: Despite verification of fatigue via torque-production decrement and shift in median frequency, no significant differences were observed in FS error for either knee flexion (pre 0.54 ± 2.28 N·m, post 0.47 ± 1.62 N·m) or extension (pre -0.28 ± 2.69 N·m, post -0.21 ± 1.78 N·m) prefatigue compared with the postfatigue condition. CONCLUSIONS: Although previous research has demonstrated that peripheral fatigue negatively affects threshold to detect passive motion (TTDPM), it did not affect FS as measured in this study. The peripheral-fatigue protocol may have a greater effect on the mechanoreceptors responsible for TTDPM than those responsible for FS. Further investigation into the effects of fatigue across various modes of proprioception is warranted.

Prediction of Dynamic Postural Stability During Single-Leg Jump Landings by Ankle and Knee Flexibility and Strength.

CONTEXT: Dynamic postural stability is important for injury prevention, but little is known about how lower-extremity musculoskeletal characteristics (range of motion [ROM] and strength) contribute to dynamic postural stability. Knowing which modifiable physical characteristics predict dynamic postural stability can help direct rehabilitation and injury-prevention programs. OBJECTIVE: To determine if trunk, hip, knee, and ankle flexibility and strength variables are significant predictors of dynamic postural stability during single-leg jump landings. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: 94 male soldiers (age 28.2 ± 6.2 y, height 176.5 ± 2.6 cm, weight 83.7 ± 26.0 kg). INTERVENTION: None. MAIN OUTCOME MEASURES: Ankle-dorsiflexion and plantar-flexion ROM were assessed with a goniometer. Trunk, hip, knee, and ankle strength were assessed with an isokinetic dynamometer or handheld dynamometer. The Dynamic Postural Stability Index (DPSI) was used to quantify postural stability. Simple linear and backward stepwise-regression analyses were used to identify which physical characteristic variables were significant predictors of DPSI. RESULTS: Simple linear-regression analysis revealed that individually, no variables were significant predictors of the DPSI. Stepwise backward-regression analysis revealed that ankle-dorsiflexion flexibility, ankle-inversion and -eversion strength, and knee-flexion and -extension strength were significant predictors of the DPSI (R2 = .19, P = .0016, adjusted R2 = .15). CONCLUSION: Ankle-dorsiflexion ROM, ankle-inversion and -eversion strength, and knee-flexion and -extension strength were identified as significant predictors of dynamic postural stability, explaining a small amount of the variance in the DPSI.

The Effect of Target Position on the Accuracy of Cervical-Spine-Rotation Active Joint-Position Sense.

CONTEXT: The cervical spine can be divided into upper and lower units, each making a different contribution to the magnitude of rotation and proprioception. However, few studies have examined the effect of the cervical-rotation positions on proprioception. OBJECTIVE: To compare cervical-spine rotation active joint-position sense (AJPS) near midrange of motion (mid-ROM; 30°) and near end-ROM (60°). DESIGN: Cross-sectional study. SETTING: Human performance research laboratory. PARTICIPANTS: 53 military helicopter pilots (age 28.4 ± 6.2 y, height 175.3 ± 9.3 cm, weight 80.1 ± 11.8 kg). MAIN OUTCOME MEASURES: A motion-analysis system was used to record cervical-rotation kinematics. Subjects sat in a chair wearing a headband and blindfold. First, they actively rotated the head right or left to a target position (30°/60°), with real-time verbal cues provided by the tester. Subjects held the target position for 5 s and then returned to the start position. After this, they replicated the target position as closely as possible. Five trials were performed in both directions to both target positions (R30/R60/L30/L60). Order of direction/position was randomized. The difference between target and replicated positions was calculated and defined as absolute error (AE), and the mean of 5 trials was used for analyses. Wilcoxon signed-ranks tests were used to compare AJPS at the different target positions (P < .0125 with Bonferroni adjustments). RESULTS: End-ROM AEs were significantly more accurate than mid-ROM AEs (P = .001). CONCLUSION: Cervical-spine-rotation AJPS is more accurate near end-ROM than mid-ROM. Both target positions should be used to examine cervical-spine-rotation AJPS of both the upper and lower units.

Salivary hormone response to 12-week block-periodized training in naval special warfare operators.

Naval Special Warfare (NSW) Operators are expected to maintain a high degree of physical readiness requiring continual operational training. The physiological and psychological demands associated with operational training can result in physiological consequences evidenced by hormonal alterations justifying the need for periodized training to maintain or improve physical readiness. This study examined the pattern and time course of hormone changes during 12-week block-periodized training program (BP) in NSW Operators undergoing routine training. Eighteen NSW Operators (31 ± 6 years, 86.6 ± 9.0 kg, 176.2 ± 5.9 cm, 17.5 ± 6.5% fat) participated in a 12-week BP during routine operational training. Salivary free testosterone (FT), dehydroepiandrosterone sulfate (DHEA-S), and cortisol (C) were obtained at 4 time points coincident with changes in intensity and volume. In the second block of training in which intensity and volume were increased, FT and C increased by 20.3 ± 7.4 and 20.8 ± 9.9%, respectively. Free testosterone and C returned to baseline values concomitant with the decrease in intensity and volume at the conclusion of the third block of training. No significant differences were observed in FT-to-C ratio over the course of training. DHEA-S increased 23.1 ± 11.0% following block 1, with a further increase observed following block 2 (57.0 ± 17.4%). Our data indicate training following BP produces a pattern and time course of hormone changes congruent with changes in intensity and volume suggesting BP as a potential training model for NSW Operators and other Special Forces Operators involved in operational training.

Neck proprioception, strength, flexibility, and posture in pilots with and without neck pain history.

INTRODUCTION: Neck pain (NP) is common among military helicopter pilots. Older age and more flight-hours have been associated with pilots with a history of NP. However, modifiable neuromuscular and musculoskeletal characteristics such as neck proprioception, strength, flexibility, and posture have rarely been investigated in military helicopter pilots with a history of NP. The purpose of the study was to compare demographics, flight characteristics, physical fitness information, neck proprioception, strength, flexibility, and posture between helicopter pilots with and without a history of NP. METHODS: A total of 27 Army helicopter pilots with NP in the past 12 mo (pain group) were matched based on age with pilots without a history of NP (nonpain group). All pilots had flown at least 100 h in the past 12 mo and were cleared for flight and physical training. All pilots completed a battery of laboratory testing: neck proprioception, neck and scapular muscular strength, neck active range-of-motion (ROM), forward head and shoulder posture, and pectoralis minor length. Paired t-tests or Wilcoxon tests were used to compare differences between groups. RESULTS: The pain group had significantly less cervical extension (63.7 +/- 8.5 degrees) and rotation ROM (R rotation: 67.7 +/- 8.8 degrees; L rotation: 67.4 +/- 9.0 degrees) when compared to the nonpain group (extension: 68.3 +/- 7.4 degrees; R rotation: 73.4 +/- 7.4 degrees; L rotation: 72.9 +/- 6.8 degrees). No significant differences were found for other variables. CONCLUSION: The results demonstrate less neck active ROM in pilots with a history of NP. Operating a helicopter with limited neck ROM or NP may negatively impact flight safety and force readiness. Continued research is warranted.

Relationship between tibial acceleration and proximal anterior tibia shear force across increasing jump distance.

Proximal anterior tibia shear force is a direct loading mechanism of the anterior cruciate ligament (ACL) and is a contributor to ACL strain during injury. Measurement of this force during competition may provide insight into risk factors for ACL injury. Accelerometers may be capable of measuring tibial acceleration during competition. The purpose of this study was to examine the relationship between acceleration measured by a tibia-mounted accelerometer and proximal anterior tibia shear force as measured through inverse dynamics and peak posterior ground reaction forces during two leg stop-jump tasks. Nineteen healthy male subjects performed stop-jump tasks across increasing jump distances. Correlation coefficients were calculated to determine if a relationship exists between accelerometer data and proximal anterior tibia shear force and peak posterior ground reaction force. An analysis of variance was performed to compare these variables across jump distance. Significant correlations were observed between accelerometer data and peak posterior ground reaction force, but none between accelerometer data and proximal anterior tibia shear force. All variables except peak proximal anterior tibia shear force increased significantly as jump distance increased. Overall, results of this study provide initial, positive support for the use of accelerometers as a useful tool for future injury prevention research.

Restoration of sagittal and transverse plane proprioception following anatomic double-bundle ACL reconstruction.

PURPOSE: To investigate the restoration of knee proprioception after anatomic double-bundle ACL reconstruction. METHODS: Eleven subjects who underwent anatomic double-bundle ACL reconstruction (12.5-15 months following surgery) and eleven healthy control subjects participated in the study. Sagittal and transverse plane threshold to detect passive motion (TTDPM) were assessed utilizing a customized isokinetic dynamometer by passively rotating the tibia about a fixed femur in both the sagittal plane and transverse plane at 0.25°/s until the subject signalled recognition of movement and movement direction. Based on the normality assumption, either dependent t test or Wilcoxon test was utilized to determine whether significant differences were present between the ACL-reconstructed and the uninjured contralateral limbs. Independent t test or Mann-Whitney test was utilized to compare between the ACL-reconstructed/uninjured contralateral and the external control limbs. RESULTS: There were no significant differences in TTDPM measurement in eleven out of twelve comparisons between the ACL-reconstructed and the uninjured contralateral/external control limbs. The only statistical significant difference was found on TTDPM towards internal rotation direction from the externally rotated-test position between the ACL-reconstructed and the uninjured contralateral limbs (p = 0.01). CONCLUSIONS: Based on a small sample of eleven subjects, the current results indicate a restoration of both sagittal and transverse plane TTDPM following the anatomic double-bundle ACL reconstruction. LEVEL OF EVIDENCE: III.

Local anaesthetics use does not suppress muscle activity following an ankle injection.

PURPOSE: To determine if peroneus longus (PL), peroneus brevis (PB), medial gastrocnemius (MG) and tibialis anterior (TA) muscle activation patterns during inversion perturbation and running tasks are suppressed following lidocaine injection to the anterior talofibular (ATF) and calcaneofibular (CF) ligament regions. METHODS: Fourteen recreationally active male subjects (age, 24.8 ± 2.9 years; height, 177.0 ± 6.0 cm; mass, 77.7 ± 6.7 kg) participated. Testing was performed under five injection conditions to the ATF and CF regions: 1 ml saline, 1 ml lidocaine, 3 ml saline, 3 ml lidocaine or no injection. Following injection condition, traditional ankle taping was applied. Electromyography patterns of the PL, PB, MG and TA were collected while subjects performed continuous lateral jumps on a custom-built device which elicited an ankle inversion perturbation and treadmill running (3.35 m s(-1), 0.5 % incline). RESULTS: No significant differences were demonstrated in muscle activation patterns of the PL (n.s.), PB (n.s.), MG (n.s.) or TA (n.s.) for any variable across injected conditions during both tasks. Statistical power was 0.214-0.526 for the PL, 0.087-0.638 for the PB, 0.115-0.560 for the MG and 0.118-0.410 for the TA. CONCLUSIONS: Injection of lidocaine up to 3 ml to the ATF and CF regions did not suppress muscle activity of the PL, PB, MG or TA during the inversion perturbation or running tasks. Injection up to 3 ml of 1 % lidocaine to the ATF and CF regions may be used without sacrificing the muscle activation patterns about the ankle. This finding is clinically relevant since the use of the injection does not put the patient at any higher risk of reinjury to the site.

The addition of body armor diminishes dynamic postural stability in military soldiers.

Poor postural stability has been identified as a risk factor for lower extremity musculoskeletal injury. The additional weight of body armor carried by Soldiers alters static postural stability and may predispose Soldiers to lower extremity musculoskeletal injuries. However, static postural stability tasks poorly replicate the dynamic military environment, which places considerable stress on the postural control system during tactical training and combat. Therefore, the purpose of this study was to examine the effects of body armor on dynamic postural stability during single-leg jump landings. Thirty-six 101st Airborne Division (Air Assault) Soldiers performed single-leg jump landings in the anterior direction with and without wearing body armor. The dynamic postural stability index and the individual stability indices (medial-lateral stability index, anterior-posterior stability index, and vertical stability index) were calculated for each condition. Paired sample t-tests were performed to determine differences between conditions. Significant differences existed for the medial-lateral stability index, anterior-posterior stability index, vertical stability index, and dynamic postural stability index (p < 0.05). The addition of body armor resulted in diminished dynamic postural stability, which may result in increased lower extremity injuries. Training programs should address the altered dynamic postural stability while wearing body armor in attempts to promote adaptations that will result in safer performance during dynamic tasks.

Reliability and Validity of a Flume-Based Maximal Oxygen Uptake Swimming Test.

A mode-specific swimming protocol to assess maximal aerobic uptake (VO2maxsw) is vital to accurately evaluate swimming performance. A need exists for reliable and valid swimming protocols that assess VO2maxsw in a flume environment. The purpose was to assess: (a) reliability and (b) "performance" validity of a VO2maxsw flume protocol using the 457-m freestyle pool performance swim (PS) test as the criterion. Nineteen males (n = 9) and females (n = 10) (age, 28.5 ± 8.3 years.; height, 174.7 ± 8.2 cm; mass, 72.9 ± 12.5 kg; %body fat, 21.4 ± 5.9) performed two flume VO2maxsw tests (VO2maxswA and VO2maxswB) and one PS test [457 m (469.4 ± 94.7 s)]. For test-retest reliability (Trials A vs. B), moderately strong relationships were established for VO2maxsw (mL·kg-1·min-1)(r= 0.628, p = 0.002), O2pulse (mL O2·beat-1)(r = 0.502, p = 0.014), VEmax (L·min-1) (r = 0.671, p = 0.001), final test time (sec) (0.608, p = 0.004), and immediate post-test blood lactate (IPE (BLa)) (0.716, p = 0.001). For performance validity, moderately strong relationships (p < 0.05) were found between VO2maxswA (r =-0.648, p = 0.005), O2pulse (r= -0.623, p = 0.008), VEmax (r = -0.509 p = 0.037), and 457-m swim times. The swimming flume protocol examined is a reliable and valid assessment of VO2maxsw., and offers an alternative for military, open water, or those seeking complementary forms of training to improve swimming performance.

Proprioceptive deficits after ACL injury: are they clinically relevant?

OBJECTIVE: To establish the clinical relevance of proprioceptive deficits reported after anterior cruciate ligament (ACL) injury. MATERIAL AND METHODS: A literature search was done in electronic databases from January 1990 to June 2009. Inclusion criteria for studies were ACL deficient (ACL-D) and ACL reconstruction (ACL-R) articles written in English, Dutch or German and calculation of correlation(s) between proprioception tests and clinical outcome measures. Clinical outcome measures were muscle strength, laxity, hop test, balance, patient-reported outcome, objective knee score rating, patient satisfaction or return to sports. Studies included in the review were assessed on their methodological quality. RESULTS: In total 1161 studies were identified of which 24 met the inclusion criteria. Pooling of all data was not possible due to substantial differences in measurement techniques and data analysis. Most studies failed to perform reliability measurements of the test device used. In general, the correlation between proprioception and laxity, balance, hop tests and patient outcome was low. Four studies reported a moderate correlation between proprioception, strength, balance or hop test. CONCLUSION: There is limited evidence that proprioceptive deficits as detected by commonly used tests adversely affect function in ACL-D and ACL-R patients. Development of new tests to determine the relevant role of the sensorimotor system is needed. These tests should ideally be used as screening tests for primary and secondary prevention of ACL injury.

Air assault soldiers demonstrate more dangerous landing biomechanics when visual input is removed.

Soldiers are subjected to increased risk of musculoskeletal injuries in night operations because of limited visual input. The purpose of this study was to determine the effect of vision removal on lower extremity kinematics and vertical ground reaction forces during two-legged drop landings. The researchers tested 139 Air Assault Soldiers performing a landing task with and without vision. Removing visual input resulted in increased hip abduction at initial contact, decreased maximum knee flexion, and increased maximum vertical ground reaction force. Without vision, the timing of maximum ankle dorsiflexion for the left leg was earlier than the right leg. The observed biomechanical changes may be related to the increased risk of injury in night operations. Proper night landing techniques and supplemental training should be integrated into Soldiers' training to induce musculoskeletal and biomechanical adaptations to compensate for limited vision.

Specificity of isokinetic assessment in noncontact knee injury prevention screening: A novel assessment procedure with relationships between variables in amateur adult agility-sport athletes.

OBJECTIVES: To present a new knee isokinetic assessment procedure linked to noncontact knee injury mechanisms and examine correlations between variables relevant to noncontact knee injury prevention screening (peak torque [PT, Nm], time-to-peak torque [TTPT, ms], angle-of-peak torque [APT, °], mean PT [MPT, Nm]). DESIGN: Cross-sectional. SETTING: Sports medicine laboratory. PARTICIPANTS: Thirty-four agility-sport athletes (male/female n = 18/16, age 24.1 ± 3.5yr, height 171.8 ± 9.6 cm, mass 70.6 ± 12 kg). MAIN OUTCOME MEASURES: Pearson's/Spearman's correlation (r/rs), coefficient of determination (r2/rs2). RESULTS: Most correlations were statistically non-significant or statistically-significant with only weak-to-moderate coefficients. For both knee extension and flexion, PT and MPT were significantly and strongly correlated (r = 0.99, r2 = 0.98, p = 0.001). Graphical analyses revealed two datapoint clusters for knee flexion TTPT and APT. One cluster indicated some participants could generate knee flexor PT rapidly (<150 ms) at low knee flexion angles (<45°) and the other cluster indicated that other participants could not (>200 ms, >50°). CONCLUSIONS: In this study, most isokinetic variables represented distinct knee neuromuscular characteristics. For both knee extension and flexion, only PT or MPT need be used to represent isokinetic maximal strength. Knee flexion TTPT and APT may have utility in noncontact knee injury prevention screening with amateur adult agility-sport athletes.

Gender Differences and the Influence of Body Composition on Land and Pool-Based Assessments of Anaerobic Power and Capacity.

Consistent differences between males and females have been shown in land-based measurements of anaerobic power and capacity. However, these differences have not been investigated for a tethered 30-s maximal swimming test (TST). The purpose of this study is to explore gender differences in land and pool-based assessments of anaerobic power (Fpeak) and capacity (Fmean), as well as the influence of body composition. Thirteen males and fifteen females completed land (Wingate (WAnT)) and pool-based (TST) measures of anaerobic power and capacity previously described in the literature. Additionally, the subjects completed assessments of body composition via air displacement plethysmography. The males produced higher force than the females for Fpeak (p < 0.001) and Fmean (p = 0.008) during the TST. However, linear regression analysis determined that lean mass significantly predicted Fpeak (p = 0.002) and Fmean (p < 0.001) during the TST, while gender was no longer significant (p = 0.694 and p = 0.136, respectively). In conclusion, increases in anaerobic power and capacity (Fpeak and Fmean) may be a function of increased lean mass in males and females, warranting future research on the impact of resistance training programs on force production and swimming performance.

Running kinematics and shock absorption do not change after brief exhaustive running.

Because of the nature of running, the forces encountered require a proper coordination of joint action of the lower extremity to dissipate the ground reaction forces and accelerations through the kinetic chain. Running-related muscle fatigue may reduce the shock absorbing capacity of the lower extremity and alter running kinematics. The purpose of this study was to determine if a bout of exhaustive running at a physiologically determined high intensity, changes running kinematics, impact accelerations, and alters shock attenuating capabilities. It was hypothesized that as a result of fatigue induced by an exhaustive run, running kinematics, impact accelerations at the head and shank, acceleration reduction, and shock attenuation would change. A within-subject, repeated-measures design was used for this study. Twelve healthy, competitive male and female distance runners participated. Subjects performed 2 testing sessions consisting of a VO2max treadmill protocol to determine the heart rate at ventilatory threshold and a fatigue-inducing running bout at the identified ventilatory threshold heart rate. Kinematic data included knee flexion, pronation, time to maximum knee flexion, and time to maximum pronation. Acceleration data included shank acceleration, head acceleration, and shock attenuation. No significant differences resulted for the kinematic or acceleration variables. Although the results of this study do not support the original hypotheses, the influence of running fatigue on kinematics and accelerations remains inconclusive. Future research is necessary to examine fatigue-induced changes in running kinematics and accelerations and to determine the threshold at which point the changes may occur.