THE RELATIONSHIP BETWEEN MUSCULOSKELETAL STRENGTH, PHYSIOLOGICAL CHARACTERISTICS, AND KNEE KINESTHESIA FOLLOWING FATIGUING EXERCISE

Fatiguing exercise may result in impaired functional joint stability and increased risk of unintentional injury. While there are several musculoskeletal and physiological characteristics related to fatigue onset, their relationship with proprioceptive changes following fatigue has not been examined. The purpose of this study was to establish the relationship between musculoskeletal and physiological characteristics and changes in proprioception, measured by threshold to detect passive motion (TTDPM), following fatiguing exercise. Twenty, physically active females participated (age: 28.65 ± 5.6 years, height: 165.6 ± 4.3 cm, weight: 61.8 ± 8.0 kg, BMI: 22.5± 2.3 kg/m2, BF: 23.3 ± 5.4%). During Visit 1, subjects completed an exercise history and 24-hour dietary questionnaire, and body composition, TTDPM familiarization, isokinetic knee strength, and maximal oxygen uptake/lactate threshold assessments. During Visit 2, subjects completed TTDPM and isometric knee strength testing prior to and following a fatiguing exercise protocol. Wilcoxon signed rank tests determined TTDPM and isometric knee strength changes from pre- to post- fatigue. Spearman’s rho correlation coefficients determined the relationship between strength and physiological variables with pre- to post-fatigue changes in TTDPM and with pre-fatigue and post-fatigue TTDPM in extension and flexion (α=0.05). No significant differences were demonstrated from pre-fatigue to post-fatigue TTDPM despite a significant decrease in isometric knee flexion strength (P<0.01) and flexion/extension ratio (P<0.05) following fatigue. No significant correlations were observed between strength or physiological variables and changes in TTDPM from pre- to post-fatigue in extension or flexion. Flexion/extension ratio was significantly correlated with pre-fatigue TTDPM in extension (r=-0.231, P<0.05). Peak oxygen uptake was significantly correlated with pre-fatigue (r=-0.500, P<0.01) and post-fatigue (r=-0.520, P<0.05) TTDPM in extension. No significant relationships were demonstrated between musculoskeletal and physiological characteristics and changes in TTDPM following fatigue. The results suggest that highly trained individuals may have better proprioception, and that the high fitness level of subjects in this investigation may have contributed to absence of TTDPM deficits following fatigue despite reaching a high level of perceptual and physiological fatigue. Future studies should consider various subject populations, other musculoskeletal strength characteristics, and different modalities of proprioception to determine the most important contributions to proprioceptive changes following fatigue

THE EFFECT OF LOADED FATIGUE ON LOADED POSTURAL STABILITY

Military personnel are often required to carry heavy loads for long distances over unpredictable terrain. Additional load carriage, in conjunction with fatigue, has the potential to influence postural control mechanisms which may in turn increase injury risk. The purpose of this study was to determine if a loaded incremental march to fatigue negatively influences loaded postural stability. Loaded postural stability was measured using the NeuroCom Sensory Organization Test (SOT) and kinetic force plate variables (vertical ground reaction forces: SDvGRF, and TotSway) before and after a loaded incremental march to fatigue in 23 physically active men and women (age: 24.1 4.0 years, height: 172.3 11.1 cm, weight: 162.2 38.2 lbs) while subjects were adorned with a weighted vest equating to 30% of their body weight. The SOT consisted of six conditions (C1-C6) aimed to perturb the sensorimotor system, which were performed before and after a loaded fatigue protocol. C1, C2 and C3 challenged the somatosensory system, C4 challenged the visual system, while C5 and C6 challenged the vestibular system. Fatigue was induced with a treadmill march at 4mph with increasing grades of 2% every three minutes until volitional fatigue. After testing for normality, paired sample t-tests or Wilcoxon signed rank tests were conducted to assess pre- to post-fatigue differences. Significant reductions in SOT scores were found in overall composite scores (pre: 82.8 4.7, post: 81.6 5.2, p = 0.010), SDvGRF of C1 (pre: 1.3 0.5, post: 2.0 0.9, p < 0.001), C2 (pre: 1.4 0.6, post: 1.9 1.2, p < 0.001), C3 (pre: 1.4 0.5, post: 2.1 1.8, p = 0.026), and C6 (pre: 2.5 2.2, post: 3.5 3.2, p < 0.001) and TotSway of all conditions. Results suggest that significant changes in loaded postural stability were caused by loaded fatigue. Findings could aid in future postural stability screenings, load carriage training and strategies for injury prevention in the military

Impact of Increased Load Carriage Magnitude on the Dynamic Postural Stability of Men and Women

The impact of load carriage on dynamic postural stability affects the survivability of the Warfighter by influencing performance capabilities and injury incidence. Further, sex may interact with the relationship between load carriage and dynamic postural stability to further compromise survivability. PURPOSE: To investigate the effect of load carriage magnitude on dynamic postural stability of men and women and its relationship to jumping ability. METHODS: 32 subjects (16 men, 16 women) were investigated for maximum jump height and dynamic postural stability. Dynamic postural stability was assessed by subjects jumping a horizontal distance of 40% their height over a 30cm hurdle, landing on one leg on a force plate (sample rate = 1200 Hz). 3 trials were completed for 3 load conditions: +0, +20 and +30% body weight (BW). Dynamic postural stability was determined from ground reaction force data during landings, by calculation of the dynamic postural stability index (DPSI). Maximum jump height was assessed by subjects performing 3 countermovement jumps (sample rate = 1000 Hz). Two-way repeated measures ANOVA were used to compare mean DPSI scores between sexes and conditions (α = 0.05). Pearson’s Correlation Coefficients were used to determine the relationship between jump height and change in DPSI scores between conditions (α = 0.05). RESULTS: Load condition significantly affected DPSI (F = 100.304, p = 0.001). DPSI scores increased between the 0% (0.359 ± 0.041), 20% (0.396 ± 0.034) and 30% (0.420 ± 0.028) BW load conditions. No significant effect of sex on DPSI was found (F = 0.131). No significant sex by load interaction on DPSI was found (F = 0.393). No significant correlations were found between jump height and change in DPSI scores between conditions. CONCLUSION: Increased load was found to negatively affect dynamic postural stability, most likely as a result of modifying the demands of the task. Therefore, the dynamic postural stability of men and women changes comparably in response to increased load carriage magnitude. Future research should focus on the effects of load on dynamic postural stability under higher loads and during more military-specific tasks

The relationship between musculoskeletal strength, physiological characteristics, and knee kinesthesia following fatiguing exercise

Fatiguing exercise may result in impaired functional joint stability and increased risk of unintentional injury. While there are several musculoskeletal and physiological characteristics related to fatigue onset, their relationship with proprioceptive changes following fatigue has not been examined. The purpose of this study was to establish the relationship between musculoskeletal and physiological characteristics and changes in proprioception, measured by threshold to detect passive motion (TTDPM), following fatiguing exercise. Twenty, physically active females participated (age: 28.65 ± 5.6 years, height: 165.6 ± 4.3 cm, weight: 61.8 ± 8.0 kg, BMI: 22.5± 2.3 kg/m 2, BF: 23.3 ± 5.4%). During Visit 1, subjects completed an exercise history and 24-hour dietary questionnaire, and body composition, TTDPM familiarization, isokinetic knee strength, and maximal oxygen uptake/lactate threshold assessments. During Visit 2, subjects completed TTDPM and isometric knee strength testing prior to and following a fatiguing exercise protocol. Wilcoxon signed rank tests determined TTDPM and isometric knee strength changes from pre- to post-fatigue. Spearman’s rho correlation coefficients determined the relationship between strength and physiological variables with pre- to post-fatigue changes in TTDPM and with pre-fatigue and post-fatigue TTDPM in extension and flexion (α=0.05). No significant differences were demonstrated from pre-fatigue to post-fatigue TTDPM despite a significant decrease in isometric knee flexion strength (P<0.01) and flexion/extension ratio (P<0.05) following fatigue. No significant correlations were observed between strength or physiological variables and changes in TTDPM from pre- to post-fatigue in extension or flexion. Flexion/extension ratio was significantly correlated with pre-fatigue TTDPM in extension (r=-0.231, P<0.05). Peak oxygen uptake was significantly correlated with pre-fatigue (r=- 0.500, P<0.01) and post-fatigue (r=-0.520, P<0.05) TTDPM in extension. No significant relationships were demonstrated between musculoskeletal and physiological characteristics and changes in TTDPM following fatigue. The results suggest that highly trained individuals may have better proprioception, and that the high fitness level of subjects in this investigation may have contributed to absence of TTDPM deficits following fatigue despite reaching a high level of perceptual and physiological fatigue. Future studies should consider various subject populations, other musculoskeletal strength characteristics, and different modalities of proprioception to determine the most important contributions to proprioceptive changes following fatigue

Epidemiology of High School Sports-related Injuries: A descriptive epidemiological study of a single high school during the 2021-2022 academic year

Millions of high school students participate in school-sanctioned athletic events each year in the United States. Participation in athletics comes with inherent adverse consequences including sports-related injury. Current epidemiological studies aim to describe the pattern of injuries between several demographic groups to enhance clinical knowledge, develop injury risk profiles, and employ prevention strategies. Purpose: The purpose of this descriptive epidemiological study was to describe patterns and incidence of anatomic location, injury type, mechanism and onset of injury, injury timing, and sport-specific injury patterns in a group of high school athletes at a private high school. The secondary and tertiary aims of this study were to compare incidence and patterns of injuries between sexes and compare incidence and patterns of injuries between single sport and interscholastic multi-sport athletes. Methods: The current study employed a descriptive epidemiological study design. Data from SOAP (subjective, objective, assessment, plan) notes were extracted and analyzed with the goal of establishing relationships between various demographic variables and incidence of sports-related injuries within a population of adolescent female and male athletes at a private high school during a single academic year. Results: The key findings of this study included a higher injury incidence for boys than girls, a higher overall incidence of acute injuries compared to chronic injuries, a higher overall incidence of non-contact injuries, and a higher incidence of injuries in football, basketball, and soccer. Furthermore, the most common injury location was the lower extremity, sprains were the most common injury. Overall, and injuries were sustained most often during practice. The percentage of interscholastic multisport (ISMA) athletes who sustained an injury (39/115 = 33.9%) was lower than the percentage of single-sport athletes who sustained an injury (40/66 = 60.6%). This difference was significant (p < 0.001). Conclusion: Adolescent participation in athletics is accompanied by inherent, often unmodifiable, risks of injury. Despite the potential negative consequences, participation in athletics provides youth with several physical, cognitive, and social benefits. Preservation of the positive impacts of sports participation may encourage continued engagement and minimize the physical and financial burden associated with sports-related injuries