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Yi-Ching Chen, I-Chen Lin, Yen-Ting Lin, Wei-Min Huang, Chien-Chun Huang and Ing-Shiou Hwang

This study contrasted the stochastic force component between young and older adults, who performed pursuit tracking/compensatory tracking by exerting in-phase/antiphase forces to match a sinusoidal target. Tracking force was decomposed into the force component containing the target frequency and the nontarget force fluctuations (stochastic component). Older adults with inferior task performance had higher complexity (entropy across time; p = .005) in total force. For older adults, task errors were negatively correlated with force fluctuation complexity (pursuit tracking: r = −.527 to −.551; compensatory tracking: r = −.626 to −.750). Notwithstanding an age-related increase in total force complexity (p = .004), older adults exhibited lower complexity of the stochastic force component than young adults did (low frequency: p = .017; high frequency: p = .035). Those older adults with a higher complexity of stochastic force had better task performance due to the underlying use of a richer gradation strategy to compensate for impaired oscillatory control.

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Marco Beato, Stuart A. McErlain-Naylor, Israel Halperin and Antonio Dello Iacono

Purpose: To summarize the evidence on postactivation potentiation (PAP) protocols using flywheel eccentric overload (EOL) exercises. Methods: Studies were searched using the electronic databases PubMed, Scopus, and Institute for Scientific Information Web of Knowledge. Results: In total, 7 eligible studies were identified based on the following results: First, practitioners can use different inertia intensities (eg, 0.03–0.11 kg·m2), based on the exercise selected, to enhance sport-specific performance. Second, the PAP time window following EOL exercise seems to be consistent with traditional PAP literature, where acute fatigue is dominant in the early part of the recovery period (eg, 30 s), and PAP is dominant in the second part (eg, 3 and 6 min). Third, as EOL exercises require large force and power outputs, a volume of 3 sets with the conditioning activity (eg, half-squat or lunge) seems to be a sensible approach. This could reduce the transitory muscle fatigue and thereby allow for a stronger potentiation effect compared with larger exercise volumes. Fourth, athletes should gain experience by performing EOL exercises before using the tool as part of a PAP protocol (3 or 4 sessions of familiarization). Finally, the dimensions of common flywheel devices offer useful and practical solutions to induce PAP effects outside of normal training environments and prior to competitions. Conclusions: EOL exercise can be used to stimulate PAP responses to obtain performance advantages in various sports. However, future research is needed to determine which EOL exercise modalities among intensity, volume, and rest intervals optimally induce the PAP phenomenon and facilitate transfer effects on athletic performances.

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Darryn S. Willoughby, Kaitlan N. Beretich, Marcus Chen and LesLee K. Funderburk

Elevated circulating C-terminal agrin fragment (CAF) is a marker of neuromuscular junction degradation and sarcopenia. This study sought to determine if resistance training (RT) impacted the serum levels of CAF in perimenopausal (PERI-M) and postmenopausal (POST-M) women. A total of 35 women, either PERI-M or POST-M, participated in 10 weeks of RT. Body composition, muscle strength, and serum estradiol and CAF were determined before and after the RT. The data were analyzed with two-way analysis of variance (p ≤ .05). Upper body and lower body strength was significantly increased, by 81% and 73% and 86% and 79% for the PERI-M and POST-M participants, respectively; however, there were no significant changes in body composition. Estradiol was significantly less for the POST-M participants at pretraining compared with the PERI-M participants. CAF moderately increased by 22% for the PERI-M participants in response to RT, whereas it significantly decreased by 49% for the POST-M participants. Ten weeks of RT reduced the circulating CAF in the POST-M women and might play a role in attenuating degenerative neuromuscular junction changes.

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Kerry E. Costello, Janie L. Astephen Wilson, William D. Stanish, Nathan Urquhart and Cheryl L. Hubley-Kozey

Both structural and clinical changes can signify knee osteoarthritis progression; however, these changes are not always concurrent. A better understanding of mechanical factors associated with progression and whether they differ for structural versus clinical outcomes could lead to improved conservative management. This study examined baseline gait differences between progression and no progression groups defined at an average of 7-year follow-up using 2 different outcomes indicative of knee osteoarthritis progression: radiographic medial joint space narrowing and total knee arthroplasty. Of 49 individuals with knee osteoarthritis who underwent baseline gait analysis, 32 progressed and 17 did not progress using the radiographic outcome, while 13 progressed and 36 did not progress using the arthroplasty outcome. Key knee moment and electromyography waveform features were extracted using principal component analysis, and confidence intervals were used to examine between-group differences in these metrics. Those who progressed using the arthroplasty outcome had prolonged rectus femoris and lateral hamstrings muscle activation compared with the no arthroplasty group. Those with radiographic progression had greater mid-stance internal knee rotation moments compared with the no radiographic progression group. These results provide preliminary evidence for the role of prolonged muscle activation in total knee arthroplasty, while radiographic changes may be related to loading magnitude.

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Kim Gammage, Desi McEwan, Lori Dithurbide, Alison Ede, Karl Erickson, Blair Evans, Larkin Lamarche, Sean Locke, Eric Martin and Kathleen Wilson

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Pai-Yun Cheng, Hsiao-Feng Chieh, Chien-Ju Lin, Hsiu-Yun Hsu, Jia-Jin J. Chen, Li-Chieh Kuo and Fong-Chin Su

This study aims toward an investigation and comparison of the digital force control and the brain activities of older adults and young groups during digital pressing tasks. A total of 15 young and 15 older adults were asked to perform force ramp tasks at different force levels with a custom pressing system. Near-infrared spectroscopy was used to collect the brain activities in the prefrontal cortex and primary motor area. The results showed that the force independence and hand function of the older adults were worse than that of the young adults. The cortical activations in the older adults were higher than those in the young group during the tasks. A significant hemodynamic between-group response and mild negative correlations between brain activation and force independence ability were found. Older adults showed poor force independence ability and manual dexterity and required additional brain activity to compensate for the degeneration.

Open access

Christopher P. Tomczyk, George Shaver and Tamerah N. Hunt

Clinical Scenario: Anxiety is a mental disorder that affects a large portion of the population and may be problematic when evaluating brain injuries such as concussion. The reliance of cognitive testing in concussion protocols call for the examination of potential cognitive alterations commonly seen in athletes with anxiety. Focused Clinical Question: Does anxiety affect neuropsychological assessments in healthy college athletes? Summary of Key Findings: Three studies were included: 1 cross-sectional study and 2 prospective cohort studies. One study examined the effect of a range of psychological issues on concussion baseline testing in college athletes. Another study examined the effect of anxiety on reaction time both before and after sport competition in college-aged athletes. The final study examined the effects of psychosocial issues on reaction time during demanding tasks in college athletes. The first study reported slower simple and complex reaction times in athletes with anxiety. The second study found that athletes with high trait anxiety have slower reaction times both before and after competition. The third study reported that demanding tasks led to increased state anxiety which slowed reaction time. Overall, all 3 studies support the adverse effect anxiety can have on cognitive testing in athletes. Clinical Bottom Line: College athletes who present with anxiety at baseline may be susceptible to decreased performance on neuropsychological assessments. Strength of Recommendation: There is level B evidence that anxiety in healthy college athletes can impact neuropsychological assessments, and level C evidence that anxiety at baseline concussion assessment impacts neuropsychological testing in college athletes.

Open access

Ryan D. Henke, Savana M. Kettner, Stephanie M. Jensen, Augustus C.K. Greife and Christopher J. Durall

ClinicalScenario: Low-intensity aerobic exercise (LIAEX) below the threshold of symptom exacerbation has been shown to be superior to rest for resolving prolonged (>4 wk) symptoms following sport-related concussion (SRC), but the effects of LIAEX earlier than 4 weeks after SRC need to be elucidated. Focused Clinical Question: Does LIAEX within the first 4 weeks following SRC hasten symptom resolution? Summary of Key Findings: Two randomized controlled trials (RCT) and 1 nonrandomized trial involving adolescent athletes (10–19 y) were included. One RCT reported faster recovery time with LIAEX versus placebo stretching. Likewise, recovery time was faster with LIAEX versus rest in the nonrandomized trial, but not in the underpowered RCT, although effect sizes were similar between these studies (0.5 and 0.4, respectively). All 3 studies reported a reduction in concussion symptom severity with LIAEX; however, the magnitude of symptom reduction across the recovery timeline was greater in the LIAEX group than the rest group in the nonrandomized trial, but not the 2 RCTs. Importantly, no adverse effects or incidence of delayed recovery from LIAEX were reported in any of the studies. Clinical Bottom Line: LIAEX initiated within 10 days after SRC may facilitate a faster recovery time versus placebo stretching or rest, although additional clinical trials are strongly advised to verify this. Strength of Recommendation: Level 1b and 2b evidence suggests subsymptom exacerbation LIAEX may decrease Postconcussion Symptom Scale scores and hasten symptom resolution in adolescent athletes following SRC.

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Kelly M. Meiners and Janice K. Loudon

Purpose/Background: Various methods are available for assessment of static and dynamic postural stability. The primary purpose of this study was to investigate the relationship between dynamic postural stability as measured by the Star Excursion Balance Test (SEBT) and static postural sway assessment as measured by the TechnoBody Pro-Kin in female soccer players. A secondary purpose was to determine side-to-side symmetry in this cohort. Methods: A total of 18 female soccer players completed testing on the SEBT and Technobody Pro-Kin balance device. Outcome measures were anterior, posterior medial, and posterior lateral reaches from the SEBT and center of pressure in the x- and y-axes as well as SD of movement in the forward/backward and medial/lateral directions from the force plate on left and right legs. Bivariate correlations were determined between the 8 measures. In addition, paired Wilcoxon signed-rank tests were performed to determine similarity between limb scores. Results: All measures on both the SEBT and postural sway assessment were significantly correlated when comparing dominant with nondominant lower-extremities with the exception of SD of movement in both x- and y-axes. When correlating results of the SEBT with postural sway assessment, a significant correlation was found between the SEBT right lower-extremity posterior lateral reach (r = .567, P < .05) and summed SEBT (r = .486, P < .05) and the center of pressure in the y-axis. A significant correlation was also found on the left lower-extremity, with SD of forward/backward movement and SEBT posterior medial reach (r = −.511, P < .05). Conclusions: Dynamic postural tests and static postural tests provide different information to the overall assessment of balance in female soccer players. Relationship between variables differed based on the subject’s lower-extremity dominance.

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Olfa Turki, Wissem Dhahbi, Sabri Gueid, Sami Hmaied, Marouen Souaifi and Riadh Khalifa

Purpose: To explore the effect of 4 different warm-up strategies using weighted vests and to determine the specific optimal recovery duration required to optimize the repeated change-of-direction (RCOD) performance in young soccer players. Methods: A total of 19 male soccer players (age 18 [0.88] y, body mass 69.85 [7.68] kg, body height 1.75 [0.07] m, body mass index 22.87 [2.23] kg·m−2, and body fat percentage 12.53% [2.59%]) completed the following loaded warm-up protocols in a randomized, counterbalanced cross-over, within-participants order and on separate days: weighted vest with a loading of 5% (WUV5%), 10% (WUV10%), 15% (WUV15%) body mass, and an unloaded condition (control). RCOD performance (total time, peak time, and fatigue index) was collected during the preintervention phase (5 min after the dynamic stretching sequence) for baseline values and immediately (at 15 min), at 4- and 8-minute postwarm-up intervention. Results: For each postwarm-up tested, recovery times (ie, 15 s, 4 min, and 8 min), of both total and peak times were faster following WUV5%, WUV10%, and WUV15%, compared with the unloaded condition (P ≤.001–.031, d = 1.28–2.31 [large]). There were no significant differences (P = .09–1.00, d = 0.03–0.72 [trivial–moderate]) in-between recovery times in both total and peak times following WUV5%, WUV10%, and WUV15%. However, baseline fatigue index score was significantly worse than all other scores (P ≤.001–.002, d = 1.35–2.46 [large]) following the loaded conditions. Conclusions: The findings demonstrated that a dynamic loaded warm-up increases an athlete’s initial RCOD performance up to the 8-minute postwarm-up intervention. Therefore, strength coaches need to consider using weighted vests during the warm-up for trained athletes in order to acutely optimize RCODs.