Skeletal muscle adaptations to high-intensity, low-volume concurrent resistance and interval training in recreationally active men and women.

This study compared the structural and cellular skeletal muscle factors underpinning adaptations in maximal strength, power, aerobic capacity, and lean body mass to a 12-week concurrent resistance and interval training program in men and women. Recreationally active women and men completed three training sessions per week consisting of high-intensity, low-volume resistance training followed by interval training performed using a variety upper and lower body exercises representative of military occupational tasks. Pre- and post-training vastus lateralis muscle biopsies were analyzed for changes in muscle fiber type, cross-sectional area, capillarization, and mitochondrial biogenesis marker content. Changes in maximal strength, aerobic capacity, and lean body mass (LBM) were also assessed. Training elicited hypertrophy of type I (12.9%; p = 0.016) and type IIa (12.7%; p = 0.007) muscle fibers in men only. In both sexes, training decreased type IIx fiber expression (1.9%; p = 0.046) and increased total PGC-1α (29.7%, p < 0.001) and citrate synthase (11.0%; p < 0.014) content, but had no effect on COX IV content or muscle capillarization. In both sexes, training increased maximal strength and LBM but not aerobic capacity. The concurrent training program was effective at increasing strength and LBM but not at improving aerobic capacity or skeletal muscle adaptations underpinning aerobic performance.

Effect of acute resistance exercise on bone turnover in young adults before and after concurrent resistance and interval training.

Weight-bearing physical activity can stimulate bone adaptation. This investigation explored the effect of an acute bout of resistance exercise before and after resistance+interval training on circulating biomarkers of bone metabolism and muscle-bone crosstalk. Healthy young male and female participants (n = 21 male, 28 ± 4 years; n = 17 female, 27 ± 5 years) performed a 6 × 10 squat test (75% 1RM) before and after a 12-week resistance+interval training program. Before and after completion of the training program, blood samples were collected at rest, immediately postexercise, and 2 h postexercise. Blood samples were analyzed for ßCTX, P1NP, sclerostin, osteocalcin, IGF-1, and irisin. Significant effects of acute exercise (main effect of time) were observed as increases in concentrations of IGF-1, irisin, osteocalcin, and P1NP from rest to postexercise. A sex*time interaction indicated a greater decline in ßCTX concentration from rest to 2 h postexercise and a greater increase in sclerostin concentration from rest to immediately postexercise in male compared with female participants. Sex differences (main effect of sex) were also observed for irisin and P1NP concentrations. In summary, changes in concentrations of biochemical markers of bone metabolism and muscle-bone crosstalk were observed in males and females after an acute bout of resistance exercise and following 12 weeks of resistance+interval training.

Comparison of physiological outcomes after dynamic exertion between athletes at return to sport from concussion and controls: Preliminary findings.

OBJECTIVES: Compare physiological (heart rate, heart rate variability, and blood pressure), performance (change-of-direction task completion time and errors), and clinical (symptoms and rating of perceived exertion) outcomes during dynamic exertion between athletes at return to sport after concussion to healthy athlete controls. DESIGN: Case control. METHODS: A sample of 23 (Female = 10; 43.5 %) athletes at medical clearance to play/activity from concussion (CONCUSS) and 23 sex-, age-, and sport-matched healthy athletes (CONTROLS) completed a 5-min seated rest before and after the dynamic exertion test. Independent sample t-tests were used to compare CONCUSS and CONTROLS for completion time, heart rate, and blood pressure; and Mann-Whitney U tests for symptoms, perceived exertion, and errors. A series of ANOVAs were conducted to compare heart rate variability between groups across pre- and post-exercise rest periods. RESULTS: There were no differences in heart rate, blood pressure, symptoms, perceived exertion, and errors. CONCUSS were faster on Zig Zag (p = .048) and Pro Agility (p = .018) tasks, reported lower symptom severity (p = .019), and had lower post-EXiT HRV (p < .049) than CONTROLS. CONCLUSIONS: Performance, symptoms, perceived exertion, and blood pressure outcomes from dynamic exertion were equivocal between athletes at medical clearance from concussion and healthy controls, which provide empirical support for dynamic exercise to inform medical clearance clinical decision making for sport-related concussion. However, differences in autonomic nervous system functioning indicate that additional research is needed to examine temporal changes in heart rate variability and other physiological outcomes following dynamic exertion.

Twelve weeks of concurrent resistance and interval training improves military occupational task performance in men and women.

In the British Army, ground close combat roles have opened to women, however, they must pass the newly developed, gender-neutral Role Fitness Tests for Soldiers (RFT(S)). Due to physiological differences between sexes, training that optimally prepares both sexes for military occupational demands and the RFT(S) is needed. The purpose of this study was to determine the efficacy of a 12-week periodized strength and power programme with concurrent interval training on RFT(S) performance and determine if performance adaptations differed between sexes. 39 recruit-aged (18-35 yrs) participants, including 21 men (29 ± 1 yrs) and 18 women (27 ± 1 yrs), completed the study. Participants performed 3 training sessions per week that included strength and power resistance training followed by interval training. Pre- to post-training, improvements were observed for seated medicine ball throw (4.5%, p < 0.001), casualty drag (29.8%, p < 0.001), single lift (8.9%, p < 0.001), water can carry (13.8%, p = 0.012), repeated lift and carry (6.5%, p < 0.001), 2-km load carriage (7.2%, p < 0.001) and 2-km run (3.2%, p = 0.021). Pre- to post-training improvements were also observed for maximal squat (27.0%, p < 0.001), bench press (8.9%, p < 0.001) and deadlift (24.6%, p < 0.001) maximal strength, but not upper body power or aerobic capacity. No differences in RFT(S) improvements were observed between sexes, however men performed better than women in all RFT(S) and physical performance measures. Concurrent resistance and interval training improves military occupational performance in men and women; however, women may need more training than men to pass the gender-neutral RFT(S).

Twelve weeks of concurrent resistance and interval training improved seated medicine ball throw, casualty drag, single lift, water can carry, repeated lift and carry, 2-km load carriage and 2-km run performance, military occupational performance measures that comprise the British Army Role Fitness Test for Soldiers (RFT(S)).Men and women demonstrated similar military occupational performance improvements from pre- to post-training, however, men performed better than women in all measures.Simple linear regression analyses between improvements in RFT(S) tasks and measures of physical fitness (one-repetition maximal strength, upper body power, lower body power, aerobic capacity) demonstrated limited significant associations suggesting that military occupational performance improvement relies on simultaneous development of multiple fitness domains.

Military tactical adaptive decision making during simulated military operational stress is influenced by personality, resilience, aerobic fitness, and neurocognitive function.

Laboratory-based studies designed to mimic combat or military field training have consistently demonstrated deleterious effects on warfighter's physical, cognitive, and emotional performance during simulated military operational stress (SMOS). Purpose: The present investigation sought to determine the impact of a 48-h simulated military operational stress (SMOS) on military tactical adaptive decision making, and the influence of select psychological, physical performance, cognitive, and physiological outcome measures on decision making performance. Methods: Male (n = 48, 26.2 ± 5.5 years, 177.7 ± 6.6 cm, 84.7 ± 14.1 kg.) subjects currently serving in the U.S. military were eligible to participate in this study. Eligible subjects completed a 96-h protocol that occurred over five consecutive days and four nights. Day 2 (D2) and day 3 (D3) consisted of 48-h of SMOS wherein sleep opportunity and caloric needs were reduced to 50%. Differences in SPEAR total block score from baseline to peak stress (D3 minus D1) were calculated to assess change in military tactical adaptive decision making and groups were stratified based on increase (high adaptors) or decrease (low adaptors) of the SPEAR change score. Results: Overall, military tactical decision-making declined 1.7% from D1 to D3 (p < 0.001). High adaptors reported significantly higher scores of aerobic capacity (p < 0.001), self-report resilience (p = 0.020), extroversion (p < 0.001), and conscientiousness (p < 0.001). at baseline compared to low adaptors, while low adaptors reported greater scores in Neuroticism (p < 0.001). Conclusion: The present findings suggest that service members whose adaptive decision making abilities improved throughout SMOS (i.e., high adaptors) demonstrated better baseline psychological/self-reported resilience and aerobic capacity. Further, changes in adaptive decision-making were distinct from those of lower order cognitive functions throughout SMOS exposure. With the transition of future military conflicts placing higher priority on enhancing and sustaining cognitive readiness and resiliency, data presented here demonstrates the importance of measuring and categorizing baseline measures inherent to military personnel, in order to change and train one's ability to suffer less of a decline during high stress conditions.

Test-Retest, Interrater Reliability, and Minimal Detectable Change of the Dynamic Exertion Test (EXiT) for Concussion.

BACKGROUND: The Dynamic Exertion Test (EXiT) was developed to inform return-to-play (RTP) decision-making following clinical recovery from sport-related concussion (SRC). The purpose of the current study was to document intrarater and test-retest reliability and minimal detectable change (MDC) scores for physiological [heart rate (HR) and blood pressure], performance (change-of-direction task completion time and errors), and clinical outcomes (endorsed symptoms, perceived exertion) of EXiT, and interrater reliability of performance outcomes. HYPOTHESIS: Healthy athletes would exhibit stable physiological responses to the EXiT across visits, demonstrate consistent change-of-direction task completion time between consecutive trials at each visit, and the fastest time (of 2 trials) across visits, and endorse equivocal symptoms and effort across visits. STUDY DESIGN: Cross-sectional, test-retest. LEVEL OF EVIDENCE: Level 3. METHODS: Seventy-nine (female: 34 [43%], 19.6 ± 5.0 years) athletes completed the EXiT at 2 study visits (8.7 ± 4.7 days between visits). Two-way, mixed, intraclass correlation coefficients (ICCs) were used to evaluate intrarater and test-retest reliability. Cronbach's alpha was used to document the internal consistency of symptoms at each visit, and MDC scores were calculated on the physiological, performance, and clinical outcomes. RESULTS: Measured and percentage of age-estimated maximum HR were reliable following EXiT (ICC = 0.579-0.618). Change-of-direction task completion time (MDC range = 0.75-8.70 s) had good-to-excellent test-retest (ICC = 0.703-0.948) and interrater (ICC = 0.932-0.965) reliability. Symptoms had a high internal consistency at visits 1 (α = 0.894) and 2 (α = 0.805) and were reliable across visits (ICC = 0.588). CONCLUSION: The current investigation established test-retest reliability in addition to MDC scores of an objective dynamic exercise assessment among healthy adolescent and adult athletes. The EXiT may be an objective approach to inform RTP decision-making following SRC recovery. CLINICAL RELEVANCE: The EXiT is a clinically feasible exertion-based assessment that can be readily administered in a variety of outpatient clinical settings.

Less daytime sleepiness and slow wave activity during sleep predict better physical readiness in military personnel.

BACKGROUND: Military personnel must maintain physical performance despite exposure to operational stressors such as sleep loss, caloric restriction and high cognitive load. Habitual sleep and specific sleep features are positively associated with fitness and may contribute to physical performance in operational settings. Further, by affecting muscle recovery, sleep may contribute to the ability to maintain performance across multiple days of exposure to operational stressors. OBJECTIVES: We examined the role of individual differences in baseline sleep on baseline physical performance and on change in physical performance throughout exposure to simulated military operational stress (SMOS). METHODS: Military personnel (36 male, 9 female, 26.3 ± 5.3 years) completed a 5-day SMOS protocol during which they completed a tactical mobility test daily. Sleep questionnaires were administered at intake and sleep was monitored each night with polysomnography. Lasso regressions were used to identify meaningful predictors of physical performance at baseline and of change in physical performance across SMOS. RESULTS: Better aerobic fitness, lower daytime sleepiness (Epworth Sleepiness Scale), and lower absolute slow wave activity (0.5-4 Hz) predicted better physical performance at baseline (66.1% of variance explained), but did not relate to changes in performance. CONCLUSIONS: Collectively, higher daytime sleepiness and slow wave activity may reflect more chronic exposure to insufficient sleep and higher baseline sleep drive, which in turn led to compromised physical performance. The findings suggest that low self-report sleepiness and low objective slow wave activity may reflect two quantifiable markers of healthy sleep behaviors that have implications for operational performance.

Combined effects of time-of-day and simulated military operational stress on perception-action coupling performance.

Perception-action coupling, the ability to 'read and react' to the environment, is essential for military personnel to operate within complex and unpredictable environments. Exposure to military operational stressors (e.g., caloric restriction, sleep loss, physical exertion), including around-the-clock operations, may compromise perception-action coupling, thereby impacting performance and safety. We examined the combined effects of simulated military operational stress (SMOS) and time-of-day on perception-action coupling. Fifty-seven active duty and reservist military personnel (45 M; 26.4 ± 5.6 years) completed a 5-day SMOS protocol that included two consecutive days of caloric restriction, and sleep restriction, and disruption. Participants completed a tablet-based perception-action coupling task (PACT) that involves perceiving whether virtual balls fit through virtual apertures. Familiarization occurred on day 0. Eight trials across day 1 (18:00, 22:00), 2 (04:00, 18:00, 22:00) and 3 (04:00, 18:00, 22:00) were analyzed. Mixed models were run to examine the interactive and main effects of day, and time-of-day on PACT response speed and accuracy outcomes. PACT response speed and accuracy outcomes improved at 18:00 and 22:00, whereas performance at 04:00 deteriorated across days. Perception-action coupling performance was resilient to SMOS, except in the early morning when the circadian drive for sleep is high, and the effects of sleep loss are more prominent.

The Role of Age, Sex, Body Mass Index, and Sport Type on the Dynamic Exertion Test in Healthy Athletes: A Cross-Sectional Study.

BACKGROUND: The dynamic exertion test (EXiT) was developed to help inform return to play after sport-related concussion, but some factors may threaten the internal validity of EXiT and affect clinical interpretation. OBJECTIVE: To compare age, sex, BMI, and sport types across EXiT physiological [pre-EXiT and post-EXiT percentage of maximum heart rate (HR %max) and blood pressure (BP)], performance (change-of-direction task completion time and committed errors), and clinical [symptoms and rating of perceived exertion (RPE)] outcomes among healthy adolescents and adults. STUDY DESIGN: Cross-sectional. METHODS: Eighty-seven participants ( F = 55, 37.4%) reported symptoms and RPE during the EXiT, which consists of a 12-minute treadmill running protocol, and the dynamic circuit, ball toss, box shuffle (SHUF) and carioca (CAR), zig zag (ZZ), proagility (PA), and arrow agility (AA) tasks. Independent samples t tests were conducted for pre-EXiT and post-EXiT HR %max and BP and change-of-direction task completion time and Mann-Whitney U tests for errors, symptoms, and RPE. A series of 1-way analysis of variance (ANOVAs) and Kruskal-Wallis H tests were conducted to compare collision, contact, and noncontact sport types. RESULTS: Adolescents had lower completion time across AA ( P = 0.01) and male athletes lower than female athletes on CAR, ZZ, PA, and AA ( P < 0.04). Male athletes reported greater RPE after the SHUF, CAR, and AA ( P < 0.03). HR %max , errors, and symptoms were equivocal across all subgroups ( P > 0.05). CONCLUSION: Age and sex should be considered in the interpretation of performance and clinical, but not physiological, EXiT outcomes. The EXiT is a standardized exercise assessment and generalizable to healthy athletes.

The Dynamic Exertion Test for Sport-Related Concussion: A Comparison of Athletes at Return-to-Play and Healthy Controls.

PURPOSE: To describe the Dynamic Exertion Test (EXiT) by comparing physiological, performance, and clinical outcomes between athletes medically cleared following sport-related concussion (SRC) and healthy controls. METHODS: One hundred four (female = 41, 39.4%) participants (14-21 y of age) including 52 medically cleared for return to play at 21.48 (15.40) days following SRC and 52 healthy athletes completed the EXiT involving (1) 12-minute aerobic component and (2) 18-minute dynamic component including 2 functional movement and 5 change-of-direction (COD) tasks. Physiological (heart rate and blood pressure), clinical (endorsed symptoms and rating of perceived exertion), and performance (COD-task completion time and errors) outcomes were collected throughout EXiT. Participants also completed the Postconcussion Symptom Scale and vestibular/ocular motor screening before EXiT. Independent-samples t tests were used to compare groups on resting heart rate and blood pressure, COD-task completion time, and Mann-Whitney U tests on Postconcussion Symptom Scale, vestibular/ocular motor screening, and EXiT symptoms, rating of perceived exertion, and errors. RESULTS: COD-task completion time and resting systolic blood pressure and heart rate were similar between groups (P > .05). SRC reported greater rating of perceived exertion during the aerobic component (P < .05) and lower total dizziness (P = .003) and total symptoms (P = .021) during EXiT and had lower near point of convergence distance (P < .001) and total symptoms (P = .007) for vestibular/ocular motor screening than healthy athletes. CONCLUSION: Physiological, performance, and clinical EXiT outcomes were equivocal between athletes at medical clearance following SRC and healthy controls. The multidomain EXiT may help to inform safe return-to-play decision making post-SRC.

The Bilateral Deficit Phenomenon in Elbow Flexion: Explanations for Its Inconsistent Occurrence and Detection.

The underlying mechanism(s) of the Bilateral Deficit (BLD) phenomenon is without consensus. Methodological inconsistencies across prior works may be an important source of equivocal results and interpretations. Based on repeatability problems with the BLD measure and maximal force definition, the presence or absence of the BLD phenomenon is altered, shifting conclusions of its mechanistic cause. Our purpose in this study was to examine methodological inconsistencies in applying the BLD measure to establish optimal methods for evaluating the underlying mechanism. Eleven healthy participants engaged in one familiarity and five test sessions, completing bilateral and unilateral elbow maximal voluntary isometric contractions. We defined maximal force by averaged and absolute peak and plateau values. BLD was evident if the bilateral index (BI), the ratio of the bilateral over summed unilateral forces, was statistically different from zero. We addressed interclass correlations (ICC), Chronbach's α, standard error of the mean, and minimal detectable change between and within sessions for all force measures and BI. We evaluated all combinations of sessions (i.e., 1-2, 3-5, 5-6) and maximal forces to establish the optimal number of sessions to achieve reliability. BLD was present for test sessions, but not for familiarization. All measures of maximal force were highly reliable between and within sessions (ICC(2,1) ≥ .895). BI was only considered significantly reliable in sessions 3-5 (p < .027), defined by absolute and average plateau forces, but reliability was still quantifiably poor (absolute: ICC(2,1) = .392; average: ICC(2,1) = .375). These results demonstrate that high force reliability within and between sessions does not translate to stable and reliable BI, potentially exposing the lack of any defined BLD mechanism.

A trait of mind: stability and robustness of sleep across sleep opportunity manipulations during simulated military operational stress.

STUDY OBJECTIVES: Within-subject stability of certain sleep features across multiple nights is thought to reflect the trait-like behavior of sleep. However, to be considered a trait, a parameter must be both stable and robust. Here, we examined the stability (i.e. across the same sleep opportunity periods) and robustness (i.e. across sleep opportunity periods that varied in duration and timing) of different sleep parameters. METHODS: Sixty-eight military personnel (14 W) spent 5 nights in the sleep laboratory during a simulated military operational stress protocol. After an adaptation night, participants had an 8-hour sleep opportunity (23:00-07:00) followed by 2 consecutive nights of sleep restriction and disruption which included two 2-hour sleep opportunities (01:00-03:00; 05:00-07:00) and, lastly, another 8-hour sleep opportunity (23:00-07:00). Intra-class correlation coefficients were calculated to examine differences in stability and robustness across different sleep parameters. RESULTS: Sleep architecture parameters were less stable and robust than absolute and relative spectral activity parameters. Further, relative spectral activity parameters were less robust than absolute spectral activity. Absolute alpha and sigma activity demonstrated the highest levels of stability that were also robust across sleep opportunities of varying duration and timing. CONCLUSIONS: Stability and robustness varied across different sleep parameters, but absolute NREM alpha and sigma activity demonstrated robust trait-like behavior across variable sleep opportunities. Reduced stability of other sleep architecture and spectral parameters during shorter sleep episodes as well as across different sleep opportunities has important implications for study design and interpretation.

Individuals with and without military-related PTSD differ in subjective sleepiness and alertness but not objective sleepiness.

Posttraumatic stress disorder-related sleep disturbances may increase daytime sleepiness and compromise performance in individuals with posttraumatic stress disorder. We investigated nighttime sleep predictors of sleepiness in Veterans with and without posttraumatic stress disorder. Thirty-seven post-9/11 Veterans with posttraumatic stress disorder and 47 without posttraumatic stress disorder (Control) completed a 48-h lab stay. Nighttime quantitative EEG and sleep architecture parameters were collected with polysomnography. Data from daytime sleepiness batteries assessing subjective sleepiness (global vigor questionnaire), objective sleepiness (Multiple Sleep Latency Tests) and alertness (psychomotor vigilance task) were included in analyses. Independent samples t-tests and linear regressions were performed to identify group differences in sleepiness and nighttime sleep predictors of sleepiness in the overall sample and within each group. Participants with posttraumatic stress disorder had higher subjective sleepiness (t = 4.20; p < .001) and lower alertness (psychomotor vigilance task reaction time (t = -3.70; p < .001) and lapses: t = -2.13; p = .04) than the control group. Objective daytime sleepiness did not differ between groups (t = -0.79, p = .43). In the whole sample, higher rapid eye movement delta power predicted lower alertness quantified by psychomotor vigilance task reaction time (ß = 0.372, p = .013) and lapses (ß = 0.388, p = .013). More fragmented sleep predicted higher objective sleepiness in the posttraumatic stress disorder group (ß = -.467, p = .005) but no other nighttime sleep measures influenced the relationship between group and sleepiness. Objective measures of sleep and sleepiness were not associated with the increased subjective sleepiness and reduced alertness of the posttraumatic stress disorder group.

Impact of simulated military operational stress on executive function relative to trait resilience, aerobic fitness, and neuroendocrine biomarkers.

PURPOSE: To study the impact of 48 h of simulated military operational stress (SMOS) on executive function, in addition to the role of trait resilience (RES) and aerobic fitness (FIT) on executive function performance. Associations between executive function and neuropeptide-Y (NPY), brain-derived neurotropic factor (BDNF), insulin-like growth factor-I (IGF-I), oxytocin, and α-klotho (klotho) were assessed to elucidate potential biomarkers that may contribute to cognitive performance during a multi-factorial stress scenario. METHODS: Fifty-four service members (SM) (26.4 ± 5.4 years, 178.0 ± 6.5 cm, 85.2 ± 14.0 kg) completed the 5-day protocol, including daily physical exertion and 48 h of restricted sleep and caloric intake. Each morning subjects completed a fasted blood draw followed by Cognition, a 10-part cognitive test battery assessing executive function. SMs were grouped into tertiles [low (L-), moderate (M-), high (H-)] based on Connor Davidson Resilience Score (RES) and V˙O2peak (FIT). Repeated measures ANOVA were run to analyze the effect of day on cognitive performance and biomarker concentration. Separate two-way mixed ANOVAs were run to determine the interaction of group by day on cognitive function. Friedman test with Bonferroni-corrected pairwise comparisons were used if assumptions for ANOVA were not met. Associations between changes in biomarkers and cognitive performance were analyzed using parametric and non-parametric correlation coefficients. RESULTS: SMOS reduced SM vigilance -11.3% (p < 0.001) and working memory -5.6% (p = 0.015), and increased risk propensity +9.5% (p = 0.005). H-RES and H-FIT SMs demonstrated stable vigilance across SMOS (p > 0.05). Vigilance was compromised during SMOS in L- and M-RES (p = 0.007 and p = 0.001, respectively) as well as L- and M-FIT (p = 0.001 and p = 0.031, respectively). SMOS reduced circulating concentrations of α-klotho -7.2% (p = 0.004), NPY -6.4% (p = 0.001), and IGF-I -8.1% (p < 0.001) from baseline through the end of the protocol. BDNF declined -19.2% after the onset of sleep and caloric restriction (p = 0.005) with subsequent recovery within 48 h. Oxytocin remained stable (p > 0.05). Several modest associations between neuroendocrine biomarkers and cognitive performance were identified. CONCLUSION: This study demonstrates H-FIT and H-RES may buffer the impact of SMOS on vigilance. SMOS negatively impacted circulating neuroendocrine biomarkers. While BDNF returned to baseline concentrations by the end of the 5 d protocol, NPY, IGF-I, and α-klotho may require a longer recovery period. These data suggest that the military may benefit by training and/or selection processes targeting at augmenting trait resilience and aerobic fitness for increased readiness.

Overnight Sleep Parameter Increases in Frontoparietal Areas Predict Working Memory Improvements in Healthy Participants But Not in Individuals With Posttraumatic Stress Disorder.

BACKGROUND: Preliminary evidence indicates that non-rapid eye movement (NREM) sleep is implicated in enhancing working memory (WM) performance across days in healthy individuals. While REM sleep has been implicated in other forms of memory, its role in WM remains unclear. Further, the relationship between sleep changes and WM improvement is largely unknown in posttraumatic stress disorder (PTSD). Examining the relationship between changes in sleep and WM improvement in healthy participants and participants with PTSD may inform cognitive enhancement strategies and intervention targets. METHODS: Repeated assessments of WM and overnight measurement of NREM and REM sleep parameters were performed in 79 participants (participants with PTSD: n = 33) during a 48-hour laboratory stay. Relationships between sleep parameter changes, WM performance changes, and clinical characteristics were analyzed in PTSD and healthy groups. RESULTS: A between-night enhancement in both NREM and REM sleep parameters in frontoparietal areas predicted across-day better WM performance in healthy participants, particularly in those with improved performance. In contrast, in participants with PTSD, an enhancement of these sleep parameters predicted a worse WM performance and was also associated with more PTSD-related sleep disturbances. CONCLUSIONS: This study shows that higher sleep activity in frontoparietal areas leads to enhanced WM performance in healthy individuals, whereas in individuals with PTSD, it likely reflects the presence of sleep disturbances that interfere with WM improvement. Interventions focused on addressing sleep disturbances could therefore ameliorate cognitive impairments in individuals with PTSD.

The effects of fatiguing exercise and load carriage on the perception and initiation of movement.

Perceptual-motor coordination relies on the accurate coupling of the perceptual and movement systems. However, individuals must also be able to recalibrate to perturbations to perceptual and movement capabilities. We examined the effects of fatigue and load carriage on perceptual-motor coordination for a maximal leaping task. 23 participants completed an incremental fatigue protocol (light to fatiguing intensity stages) on two separate occasions (loaded/unloaded). At baseline and the end of every stage of the protocol, participants made perceptual judgments for the affordance of leaping. The accuracy of responses and reaction times were calculated and mean differences were assessed across exercise intensity and load carriage conditions. No interaction of exercise intensity and load carriage was detected, or main effect of load carriage. A main, quadratic effect of exercise intensity was detected on reaction times, with times decreasing through the moderate stage and increasing through post-fatigue. No effect of exercise/fatigue was detected on perceptual accuracy. The results indicate that exercise at high intensities through fatigue has a significant effect on perceptual-motor calibration. Contrastingly, in response to an action-scaled task, individuals can adequately recalibrate to increased load carriage.

You Snooze, You Win? An Ecological Dynamics Framework Approach to Understanding the Relationships Between Sleep and Sensorimotor Performance in Sport.

Sleep has a widespread impact across different domains of performance, including sensorimotor function. From an ecological dynamics perspective, sensorimotor function involves the continuous and dynamic coupling between perception and action. Sport performance relies on sensorimotor function as successful movement behaviors require accurate and efficient coupling between perceptions and actions. Compromised sleep impairs different aspects of sensorimotor performance, including perceptual attunement and motor execution. Changes in sensorimotor performance can be related to specific features of sleep, notably sleep spindles and slow waves. One unaddressed area of study is the extent to which specific sleep features contribute to overall sport-specific performance.

Action Boundary Proximity Effects on Perceptual-Motor Judgments.

INTRODUCTION: Designed as a more ecological measure of reaction times, the Perception-Action Coupling Task (PACT) has shown good reliability and within-subject stability. However, a lengthy testing period was required. Perceptual-motor judgments are known to be affected by proximity of the stimulus to the action boundary. The current study sought to determine the effects of action boundary proximity on PACT performance, and whether redundant levels of stimuli, eliciting similar responses, can be eliminated to shorten the PACT.METHODS: There were 9 men and 7 women who completed 4 testing sessions, consisting of 3 familiarization cycles and 6 testing cycles of the PACT. For the PACT, subjects made judgments on whether a series of balls presented on a tablet afford "posting" (can fit) through a series of apertures. There were 8 ratios of ball to aperture size (B-AR) presented, ranging from 0.2 to 1.8, with each ratio appearing 12 times (12 trials) per cycle. Reaction times and judgment accuracy were calculated, and averaged across all B-ARs. Ratios and individual trials within each B-AR were systematically eliminated. Variables were re-averaged, and intraclass correlation coefficients (ICC) and coefficients of variation (CVTE) were calculated in an iterative manner.RESULTS: With elimination of the 0.2 and 1.8 B-ARs, the PACT showed good reliability (ICC = 0.81-0.99) and consistent within-subject stability (CVTE = 2.2-14.7%). Reliability (ICC = 0.81-0.97) and stability (CVTE = 2.6-15.6%) were unaffected with elimination of up to 8 trials from each B-AR.DISCUSSION: The shortened PACT resulted in an almost 50% reduction in total familiarization/testing time required, significantly increasing usability.Johnson CD, LaGoy AD, Pepping G-J, Eagle SR, Beethe AZ, Bower JL, Alfano CA, Simpson RJ, Connaboy C. Action boundary proximity effects on perceptual-motor judgments. Aerosp Med Hum Perform. 2019; 90(12):1000-1008.