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1.
Eur J Clin Nutr ; 78(5): 420-426, 2024 May.
Article in English | MEDLINE | ID: mdl-38402354

ABSTRACT

BACKGROUND/OBJECTIVES: Emerging adults (~18-28 years of age) have a high prevalence of poor sleeping habits and poor diet quality; however, little is known on whether these poor sleeping habits are associated with dietary outcomes in this age group. This study assessed associations between actigraphy-based sleep with energy intake (EI), overall diet quality, and measures of meal timing in emerging adults. SUBJECTS/METHODS: Data on 135 emerging adults (age = 19.4 ± 1.3 years; body mass index (BMI) = 26.5 ± 6.9 kg/m2; 58% female; 65% White) from the RIGHT Track Health project were used. Measures included actigraphy-assessed sleep duration, sleep efficiency, sleep timing midpoint, day-to-day sleep duration and sleep timing midpoint variability and combined sleep duration and sleep timing behaviors (early-bed/late-rise, early-bed/early-rise, late-bed/late-rise, late-bed/early-rise); EI (three 24-h dietary recalls), diet quality (Healthy Eating Index 2015 total score) and meal timing outcomes (timing of first and last meal intake, total duration, and midpoint of the eating window). RESULTS: Shorter sleep duration, later sleep timing midpoint and greater sleep efficiency, as well as combined late-bed/late-rise and late-bed/early-rise groups, were associated with lower diet quality. Greater sleep timing midpoint variability was associated with higher EI, and the late-bed/early-rise group had significantly delayed first meal timing. CONCLUSION: In emerging adults, shorter sleep duration and later sleep timing are associated with lower overall diet quality, and greater sleep timing variability is associated with higher EI. Future research is needed to examine the role of sleep on diet quality and eating habits to identify potential targets for nutritional interventions in this age group.


Subject(s)
Actigraphy , Diet , Sleep , Humans , Female , Male , Young Adult , Sleep/physiology , Cross-Sectional Studies , Adult , Diet/methods , Adolescent , Feeding Behavior/physiology , Energy Intake , Meals , Body Mass Index
2.
J Sleep Res ; 33(2): e14068, 2024 Apr.
Article in English | MEDLINE | ID: mdl-37803814

ABSTRACT

This study assessed associations of actigraphy-assessed sleep with adiposity and serum cardiometabolic outcomes in emerging adults, and whether sex and race modified these associations. Data on 147 emerging adults (age = 19.4 ± 1.3 years; body mass index = 26.4 ± 7.0 kg m-2 ; 59% female; 65% White) from RIGHT Track Health were used. Actigraphy-based sleep measures included sleep duration, sleep efficiency, sleep timing midpoint, day-to-day sleep duration and sleep timing midpoint variability. Combined sleep duration and sleep timing behaviours were also derived (early-bed/late-rise, early-bed/early-rise, late-bed/late-rise, late-bed/early-rise). Outcomes included body mass index and BodPod-assessed fat mass index, fasting serum leptin, C-reactive protein, and homeostatic model assessment-insulin resistance. Sleep duration was 5.4 h per night. We noted an inverse association between sleep duration and homeostatic model assessment-insulin resistance. The early-bed/early-rise group had greater body mass index, C-reactive protein and homeostatic model assessment-insulin resistance compared with the early-bed/late-rise group (referent). Sex modified associations of sleep efficiency with C-reactive protein; stratified results revealed positive association between sleep efficiency and C-reactive protein in males, but not females. Race modified associations of sleep duration with body mass index and leptin, and of sleep duration variability with C-reactive protein. Stratified analyses revealed inverse associations between sleep duration with body mass index and leptin in Black, multiracial/other race individuals only. Positive association between sleep duration variability and C-reactive protein was noted in White individuals only. Shorter sleep duration, particularly when combined with earlier sleep timing, is associated with greater adiposity and serum cardiometabolic outcomes. Additional studies are needed to assess individual- and contextual-level factors that may contribute to sex and race differences in sleep health and cardiometabolic risk in emerging adults.


Subject(s)
Cardiovascular Diseases , Insulin Resistance , Male , Adult , Humans , Female , Adolescent , Young Adult , Adiposity , Leptin , Actigraphy , C-Reactive Protein , Obesity/complications , Sleep , Body Mass Index
3.
Sensors (Basel) ; 23(14)2023 Jul 11.
Article in English | MEDLINE | ID: mdl-37514591

ABSTRACT

Brain-body interactions (BBIs) have been the focus of intense scrutiny since the inception of the scientific method, playing a foundational role in the earliest debates over the philosophy of science. Contemporary investigations of BBIs to elucidate the neural principles of motor control have benefited from advances in neuroimaging, device engineering, and signal processing. However, these studies generally suffer from two major limitations. First, they rely on interpretations of 'brain' activity that are behavioral in nature, rather than neuroanatomical or biophysical. Second, they employ methodological approaches that are inconsistent with a dynamical systems approach to neuromotor control. These limitations represent a fundamental challenge to the use of BBIs for answering basic and applied research questions in neuroimaging and neurorehabilitation. Thus, this review is written as a tutorial to address both limitations for those interested in studying BBIs through a dynamical systems lens. First, we outline current best practices for acquiring, interpreting, and cleaning scalp-measured electroencephalography (EEG) acquired during whole-body movement. Second, we discuss historical and current theories for modeling EEG and kinematic data as dynamical systems. Third, we provide worked examples from both canonical model systems and from empirical EEG and kinematic data collected from two subjects during an overground walking task.


Subject(s)
Brain , Electroencephalography , Humans , Electroencephalography/methods , Brain Mapping/methods , Walking , Systems Analysis
4.
Entropy (Basel) ; 24(8)2022 Jul 29.
Article in English | MEDLINE | ID: mdl-36010709

ABSTRACT

The objective of this study was to examine cardio hypothalamic-pituitary coupling and to better understand how the temporal relations between these systems are altered during rest and exercise conditions. An intensive within subjects study design was used. Seven adult males completed two visits, each consisting of either a 24 h period of complete rest or a 24 h period containing a high-intensity exercise bout. An intravenous catheter was used to collect serum samples every 10 min throughout the 24 h period (i.e., 145 samples/person/condition) to assess growth hormone (GH) dynamics throughout the 24 h period. Cardiac dynamics were also collected throughout the 24 h period and epoched into 3 min windows every 10 min, providing serial short-time measurements of heart rate variability (HRV) concurrent to the GH sampling. The standard deviation of the normal RR interval (SDNN), the root mean square of successive differences (rMSSD), and sample entropy (SampEn) was calculated for each epoch and used to create new profiles. The dynamics of these profiles were individually quantified using SampEn and recurrence quantification analysis (RQA). To address our central question, the coupling between these profiles with GH was assessed using cross-SampEn and cross-RQA (cRQA). A comparison between the epoched HRV profiles indicated a main effect between profiles for sample entropy (p < 0.001) and several measures from RQA. An interaction between profile and condition was observed for cross-SampEn (p = 0.04) and several measures from cRQA. These findings highlight the potential application of epoched HRV to assess changes in cardiac dynamics, with specific applications to assessing cardio hypothalamic-pituitary coupling.

5.
Front Sports Act Living ; 3: 692691, 2021.
Article in English | MEDLINE | ID: mdl-34386767

ABSTRACT

Monitoring session training load to optimize the training stress that drives athlete adaptation and subsequent performance, is fundamental to periodization and programming. Analyzing the internal load experienced by the individual in response to the external load prescribed by coaching staff is crucial to avoid overtraining and optimize training adaptation. Subjective measures provide more information regarding individual training load, as heart rate measures alone do not account for collisions, eccentric muscle actions, muscle soreness, weather conditions, or accumulated training loads, which are paramount to the athlete experience. However, the current subjective metric for interpreting session training load (sRPE) is poorly shaped to the athlete's global response to the whole session, often showing poorer correlations to heart rate (HR) measures during intermittent or high-intensity activity. This study introduces a new metric, the Global Session Metric Score (GSMs), which creates a symmetrical relation between the verbal descriptor and numeric values, as well as more applicable session-specific verbal descriptors for the highest level of exertion. Twenty-four D1 male college soccer field players (age: 20.5 +/- 1.42) wore HR monitors and reported GSMs for all practices and games within an entire season. Linear regression with 10-fold cross validation was used to test the relation between GSMs with B-TRIMP and E-TRIMP, respectively. These models demonstrate good performance with consistency and reliability in the estimation of GSMs to predict both B-TRIMP (R 2 = 0.75-0.77) and E-TRIMP (R 2 = 0.76-0.78). The findings show promise for the GSMs index as a reliable means for measuring load in both training and matches during a high-intensity intermittent team sport. Future studies should directly compare GSMs to the existing sRPE scale within a controlled laboratory setting and across various other sports. GSMs provides coaches and clinicians a simple and cost-effective alternative to heart rate monitors, as well as a proficient measure of internal training load experienced by the individual.

6.
Sensors (Basel) ; 21(13)2021 Jun 26.
Article in English | MEDLINE | ID: mdl-34206782

ABSTRACT

(1) Background: Biomechanics during landing tasks, such as the kinematics and kinetics of the knee, are altered following anterior cruciate ligament (ACL) injury and reconstruction. These variables are recommended to assess prior to clearance for return to sport, but clinicians lack access to the current gold-standard laboratory-based assessment. Inertial sensors serve as a potential solution to provide a clinically feasible means to assess biomechanics and augment the return to sport testing. The purposes of this study were to (a) develop multi-sensor machine learning algorithms for predicting biomechanics and (b) quantify the accuracy of each algorithm. (2) Methods: 26 healthy young adults completed 8 trials of a double limb jump landing task. Peak vertical ground reaction force, peak knee flexion angle, peak knee extension moment, and peak sagittal knee power absorption were assessed using 3D motion capture and force plates. Shank- and thigh- mounted inertial sensors were used to collect data concurrently. Inertial data were submitted as inputs to single- and multiple- feature linear regressions to predict biomechanical variables in each limb. (3) Results: Multiple-feature models, particularly when an accelerometer and gyroscope were used together, were valid predictors of biomechanics (R2 = 0.68-0.94, normalized root mean square error = 4.6-10.2%). Single-feature models had decreased performance (R2 = 0.16-0.60, normalized root mean square error = 10.0-16.2%). (4) Conclusions: The combination of inertial sensors and machine learning provides a valid prediction of biomechanics during a double limb landing task. This is a feasible solution to assess biomechanics for both clinical and real-world settings outside the traditional biomechanics laboratory.


Subject(s)
Anterior Cruciate Ligament Injuries , Knee Joint , Biomechanical Phenomena , Humans , Knee , Machine Learning , Young Adult
7.
Front Physiol ; 12: 627320, 2021.
Article in English | MEDLINE | ID: mdl-33613320

ABSTRACT

INTRODUCTION: Resting heart rate (HRrest), heart rate variability (HRV), and HR recovery (HRR) from exercise provide valuable information about cardiac autonomic control. RR-intervals during acute recovery from exercise (RRrec) are commonly excluded from HRV analyses due to issues of non-stationarity. However, the variability and complexity within these trends may provide valuable information about changes in HR dynamics. PURPOSE: Assess the complexity of RRrec and determine what physiologic and demographic information are associated with differences in these indices in young adults. METHODS: RR-intervals were collected throughout maximal treadmill exercise and recovery in young adults (n = 92). The first 5 min of RRrec were (1) analyzed with previously reported methods that use 3-interval lengths for comparison and (2) detrended using both differencing(diff) and polynomial regression(res). The standard deviation of the normal interval (SDNN), root mean square of successive differences (rMSSD), root mean square (RMS) of the residual of regression, and sample entropy (SampEn) were calculated. Repeated measures analysis of covariance (ANCOVA) tested for differences in these indices for each of the methodological approaches, controlling for race, body fat, peak oxygen uptake (VO2p eak), and resting HR (HRrest). Statistical significance was set at p < 0.05. RESULTS: VO2p eak and HRrest were significantly correlated with traditional measures of HRR and the variability surrounding RRrec. SampEndiff and SampEnres were correlated with VO2p eak but not HRrest or HRR. The residual-method provided a significantly (p = 0.04) lower mean standard error (MSE) (0.064 ± 0.042) compared to the differencing-method (0.100 ± 0.033). CONCLUSIONS: Complexity analysis of RRrec provides unique information about cardiac autonomic regulation immediately following the cessation of exercise when compared to traditional measures of HRR and both HRrest and VO2peak influence these results.

8.
Nonlinear Dynamics Psychol Life Sci ; 24(4): 367-387, 2020 Oct.
Article in English | MEDLINE | ID: mdl-32960753

ABSTRACT

Heart rate variability (HRV) is a noninvasive marker of cardiac autonomic function that has been extensively studied in a variety of populations. However, HRV analyses require stationarity-thus, limiting the conditions in which these data can be analyzed in physiologic and health research (e.g. post-exercise). To provide evidence and clarity on how non-stationarity affects popular indices of variability and complexity. Simulations within physiologic (restricted to values similar to exercise and recovery RR-intervals) and non-physiologic parameters, with homoscedastic and heteroscedastic variances, across four sample lengths (200, 400, 800, and 2000), and four trends (stationary, positive-linear, quadratic, and cubic) were detrended using 1-3 order polynomials and sequential differencing. Measures of variability [standard deviation of normal intervals (SDNN) and root mean square of successive differences (rMSSD)] as well as complexity [sample entropy (SampEn)] were calculated on each of the raw and detrended time-series. Differential effects of trend, length, and fit were observed between physiologic and non-physiologic parameters. rMSSD was robust against trends within physiologic parameters while both SDNN and SampEn were positively and negatively biased by trend, respectively. Within non-physiologic parameters, the SDNN, rMSSD, and SampEn of the raw time-series were all biased, highlighting the effect of the scale between these two sets of parameters. However, indices of variability and complexity on the original (trended) times-series were furthest from those of the stationary time-series, with indices coming closer to the known values as fit become more optimal. Detrending with polynomial functions provide reliable and accurate methods of assessing the variability and complexity of non-stationary time-series-such as those immediately following exercise.


Subject(s)
Autonomic Nervous System , Exercise , Entropy , Heart Rate , Humans
9.
BMC Neurol ; 20(1): 231, 2020 Jun 06.
Article in English | MEDLINE | ID: mdl-32503473

ABSTRACT

BACKGROUND: By 2050, the prevalence of Alzheimer's disease (AD) in the United States is predicted to reach 13.8 million. Despite worldwide research efforts, a cure for AD has not been identified. Thus, it is critical to identify preventive strategies that can reduce the risk of or delay the onset of AD. Physical activity (PA) has potential in this regard. This randomized clinical trial aims to (a) test the causal relationship between PA and AD-associated cognitive function for persons with a family history of AD (FH+), (b) determine the moderating role of apolipoprotein epsilon 4 (APOE4) carrier status on cognition, and (c) assess cerebral structure, cerebral function, and putative biomarkers as mediators of the effects of PA on cognition. METHODS: We are recruiting cognitively normal, middle aged (40-65 years) sedentary adults with FH+. Participants are randomly assigned to a 12-month PA intervention for 3 days/week or to a control group maintaining their normal lifestyle. Saliva samples are taken at pre-test to determine APOE genotype. At pre-, mid-, and post-tests, participants complete a series of cognitive tests to assess information-processing speed, verbal and visual episodic memory, constructional praxis, mnemonic discrimination, and higher-order executive functions. At pre- and post-tests, brain imaging and blood biomarkers are assessed. DISCUSSION: We hypothesize that 1) the PA group will demonstrate improved cognition compared with controls; 2) PA-derived cognitive changes will be moderated by APOE4 status; and 3) PA-induced changes in neural and blood biomarkers will contribute to cognitive changes and differ as a function of APOE4 status. Our results may provide important insights into the potential of PA to preserve neurocognitive function in people with a heightened risk of AD due to FH+ and as moderated by APOE4 status. By using sophisticated analytic techniques to assess APOE as a moderator and neurobiological mechanisms as mediators across trajectories of cognitive change in response to PA, we will advance our understanding of the potential of PA in protecting against AD. TRIAL REGISTRATION: ClinicalTrials.gov NCT03876314. Registered March 15, 2019.


Subject(s)
Alzheimer Disease , Apolipoproteins E/genetics , Cognition/physiology , Exercise Therapy , Exercise/physiology , Adult , Aged , Alzheimer Disease/genetics , Alzheimer Disease/therapy , Brain/diagnostic imaging , Brain/pathology , Genotype , Humans , Middle Aged
10.
Dev Psychol ; 56(4): 783-794, 2020 Apr.
Article in English | MEDLINE | ID: mdl-31999180

ABSTRACT

Parasympathetic nervous system functioning as indexed by respiratory sinus arrhythmia (RSA) is widely used as a measure of physiological regulation. We examined developmental patterns of children's resting RSA and RSA reactivity from 2 to 15 years of age, a period of time that is marked by considerable advances in children's regulatory abilities. Physiological data were collected from a community sample of 270 children (116 males) during a resting period and during a frustration laboratory task when the children were 2, 4, 5, 7, 10, and 15 years old. We examined both stability and continuity in resting RSA and RSA reactivity across time. We found stability in resting RSA but not RSA reactivity from toddlerhood to adolescence. Separate multilevel models were used to examine changes in resting RSA and RSA reactivity from Age 2 to Age 15. The rate of change in resting RSA slowed from Age 2 to Age 15 with a plateau around Age 10. A splined growth model indicated that the rate of RSA reactivity increased from Age 2 to Age 7 and a modest slowing and leveling off from Age 7 to Age 15. Understanding the developmental characteristics of RSA across childhood and adolescence is important to understanding the larger constructs of self- and emotion regulation. (PsycINFO Database Record (c) 2020 APA, all rights reserved).


Subject(s)
Adolescent Development/physiology , Child Development/physiology , Parasympathetic Nervous System/physiology , Respiratory Sinus Arrhythmia/physiology , Adolescent , Child , Child, Preschool , Female , Humans , Longitudinal Studies , Male
11.
Eur J Sport Sci ; 20(6): 819-830, 2020 Jul.
Article in English | MEDLINE | ID: mdl-31495276

ABSTRACT

Little is known about the biological mechanisms underlying the beneficial effect of acute exercise on memory or the influence of single nucleotide polymorphisms (SNPs) on this effect. Brain-derived neurotrophic factor (BDNF) is a putative biological mechanism, and while findings from human studies are equivocal, they have neglected to assess how exercise affects individual BDNF isoform (proBDNF, mBDNF) concentrations in serum or the influence of the BDNF val66met SNP on BDNF isoform concentrations. Therefore, the objective of this study was to conduct an exploratory assessment of the effect of acute exercise intensity on memory performance and BDNF isoform concentrations relative to carrier status of the BDNF val66met SNP met allele and to provide guidance for future, fully-powered trials. Memory and BDNF isoform concentrations were assessed in three exercise groups (light intensity, vigorous intensity, and non-exercise) relative to BDNF met carrier status. Analyses revealed that BDNF isoform concentrations and memory were differentially affected by exercise intensity and BDNF met carrier status. Vigorous intensity exercise increased mBDNF, and BDNF met carriers had lower mBDNF concentration. Light intensity exercise improved memory, and over 24 h, memory was worse for BDNF met carriers. Implications from this work will help direct future mechanistic studies of the exercise-memory relationship.


Subject(s)
Brain-Derived Neurotrophic Factor/blood , Exercise/physiology , Memory/physiology , Polymorphism, Single Nucleotide , Adolescent , Adult , Alleles , Brain-Derived Neurotrophic Factor/genetics , Heart Rate , Heterozygote , Humans , Male , Memory, Short-Term/physiology , Preliminary Data , Protein Isoforms/blood , Protein Isoforms/genetics , Protein Precursors/blood , Protein Precursors/genetics , Retention, Psychology , Spatial Memory/physiology , Time Factors , Verbal Learning/physiology , Young Adult
12.
Int J Exerc Sci ; 11(5): 84-94, 2018.
Article in English | MEDLINE | ID: mdl-29997736

ABSTRACT

The purpose of our study was to examine if the beneficial effects of an external focus are effective for balance control when sleep-deprived. Sleep-deprived participants (27 hours awake) completed three blocks of five separate 30 second trials on a dynamic balance board. All participants were given internal, external, and control instruction. For the internal focus trials, participants focused on their feet; whereas, for the external focus trials, participants focused on the balance board. Participants' time in balance was significantly greater during the external focus compared to the internal focus and control. These findings suggest that external focus instructions are effective when participants are sleep-deprived.

13.
PLoS One ; 13(1): e0191331, 2018.
Article in English | MEDLINE | ID: mdl-29351335

ABSTRACT

The incidence of pre-diabetes (PD) and Type-2 Diabetes Mellitus (T2D) is a worldwide epidemic. African American (AA) individuals are disproportionately more likely to become diabetic than other ethnic groups. Over the long-term, metabolic complications related to diabetes result in significant alterations in growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Considering the limited exercise-related studies in the area of gene expression changes with disease progression, the objective of this study was to examine differences in exercise-induced gene expression related to the GH and IGF-1 pathways in peripheral blood mononuclear cells (PBMCs) of healthy (CON) and PD AA individuals. DESIGN: Ten subjects [5 PD (age = 35±9.3 yr, BMI = 32.1±4.0, FBG = 101.8±1.3 mg/dl) and 5 CON (age = 31±9.4 yr, BMI = 29.4±5.2, FBG = 82.8±9.7 mg/dl)] had blood drawn for RNA isolation prior to exercise (Pre), immediately following acute moderate intensity exercise on a treadmill (Post-1), 6-hours post (Post-6), and 24-hours post (Post-24). Isolation of mRNA from PBMCs was performed using ficoll separation, while the profiling of mRNA expression was performed using Illumina beadchip arrays with standard protocols. Scan results were statistically analyzed for a specific list of genes related to GH and IGF-1. GH and IGF-1 protein levels were also assessed in each sample. To address issues of normality, all GH and IGF-1 data were log-transformed prior to analysis. Statistical significance was set at p<0.05. RESULTS: Group differences for GH2 variant 2 (p = 0.070) and GH2 variant 3 (p = 0.059) were coupled with significant alterations in IGF-1 mRNA over time (p = 0.024). A significant interaction between group and time was observed for GHRH mRNA (p = 0.008). No group differences were observed in GH AUC (p = 0.649), ΔGH (p = 0.331), GHrec (p = 0.294), or IGF-1 AUC (p = 0.865), representing a similar exercise-induced GH and IGF-1 response for both groups. CONCLUSIONS: Analysis of GH and IGF-1 related-gene expression indicates that mild elevations in fasting blood glucose and exercise-induced alterations in gene expression are impacted by the prediabetic state.


Subject(s)
Black or African American/genetics , Gene Expression Regulation , Human Growth Hormone/genetics , Insulin-Like Growth Factor I/genetics , Prediabetic State/genetics , Adult , Blood Glucose/metabolism , Case-Control Studies , Fasting/blood , Female , Human Growth Hormone/metabolism , Humans , Insulin-Like Growth Factor I/metabolism , Male , Pilot Projects , Prediabetic State/blood , Prediabetic State/metabolism , Prediabetic State/physiopathology , Protein Transport , RNA, Messenger/genetics , RNA, Messenger/metabolism , Time Factors
14.
Undersea Hyperb Med ; 44(6): 589-600, 2017.
Article in English | MEDLINE | ID: mdl-29281196

ABSTRACT

BACKGROUND: The influence of prolonged and repeated water immersions on heart rate variability (HRV) and complexity was examined in 10 U.S. Navy divers who completed six-hour resting dives on five consecutive days. Pre-dive and during-dive measures were recorded daily. METHODS: Dependent variables of interest were average heart rate (HR), time-domain measures of HRV [root mean square of successive differences of the normal RR (NN) interval (RMSSD), standard deviation of the NN interval (SDNN)], frequency-domain measures of HRV [low-frequency power spectral density (psd) (LFpsd), low-frequency normalized (LFnu), high-frequency psd (HFpsd), high-frequency normalized (HFnu), low-frequency/ high-frequency ratio (LF/HF)], and non-linear dynamics of HRV [approximate entropy (ApEn)]. A repeated-measures ANOVA was performed to examine pre-dive measure differences among baseline measures. Hierarchical linear modeling (HLM) was performed to test the effects of prolonged and repeated water immersion on the dependent variables. RESULTS: Pre-dive HR (P=0.005) and RMSSD (P⟨0.001) varied significantly with dive day while changes in SDNN approached significance (P=0.055). HLM indicated that HR decreased during daily dives (P=0.001), but increased across dive days (P=0.011); RMSSD increased during daily dives (P=0.018) but decreased across dive days (P⟨0.001); SDNN increased during daily dives (P⟨0.001); LF measures increased across dive days (LFpsd P⟨0.001; LFnu P⟨0.001), while HF measures decreased across dive days (HFpsd P⟨0.001; HFnu P⟨0.001); LF/HF increased across dive days (P⟨0.001); ApEn decreased during daily dives (P⟨0.02) and across dive days (P⟨0.001). CONCLUSIONS: These data suggest that the cumulative effect of repeated dives across five days results in decreased vagal tone and a less responsive cardiovascular system.


Subject(s)
Diving/adverse effects , Diving/physiology , Heart Rate/physiology , Immersion/adverse effects , Immersion/physiopathology , Military Personnel , Adult , Analysis of Variance , Electrocardiography/statistics & numerical data , Humans , Linear Models , Male , Models, Cardiovascular , Monitoring, Physiologic/statistics & numerical data , Stress, Physiological , United States , Young Adult
15.
J Sports Sci Med ; 15(2): 247-53, 2016 Jun.
Article in English | MEDLINE | ID: mdl-27274661

ABSTRACT

Multisport events continue to grow in popularity among recreational, amateur, and professional athletes around the world. This study aimed to determine the compounding effects of the initial run and cycling legs of an International Triathlon Union (ITU) Duathlon simulation on maximal oxygen uptake (VO2max), ventilatory threshold (VT) and running economy (RE) within a thermoneutral, laboratory controlled setting. Seven highly trained multisport athletes completed three trials; Trial-1 consisted of a speed only VO2max treadmill protocol (SOVO2max) to determine VO2max, VT, and RE during a single-bout run; Trial-2 consisted of a 10 km run at 98% of VT followed by an incremental VO2max test on the cycle ergometer; Trial-3 consisted of a 10 km run and 30 km cycling bout at 98% of VT followed by a speed only treadmill test to determine the compounding effects of the initial legs of a duathlon on VO2max, VT, and RE. A repeated measures ANOVA was performed to determine differences between variables across trials. No difference in VO2max, VT (%VO2max), maximal HR, or maximal RPE was observed across trials. Oxygen consumption at VT was significantly lower during Trial-3 compared to Trial-1 (p = 0.01). This decrease was coupled with a significant reduction in running speed at VT (p = 0.015). A significant interaction between trial and running speed indicate that RE was significantly altered during Trial-3 compared to Trial-1 (p < 0.001). The first two legs of a laboratory based duathlon simulation negatively impact VT and RE. Our findings may provide a useful method to evaluate multisport athletes since a single-bout incremental treadmill test fails to reveal important alterations in physiological thresholds. Key pointsDecrease in relative oxygen uptake at VT (ml·kg(-1)·min(-1)) during the final leg of a duathlon simulation, compared to a single-bout maximal run.We observed a decrease in running speed at VT during the final leg of a duathlon simulation; resulting in an increase of more than 2 minutes to complete a 5 km run.During our study, highly trained athletes were unable to complete the final 5 km run at the same intensity that they completed the initial 10 km run (in a laboratory setting).A better understanding, and determination, of training loads during multisport training may help to better periodize training programs; additional research is required.

16.
J Strength Cond Res ; 26(8): 2027-36, 2012 Aug.
Article in English | MEDLINE | ID: mdl-21997450

ABSTRACT

An observed relationship between soccer match duration and injury has led to research examining the changes in lower extremity mechanics and performance with fatiguing exercise. Because many fatigue protocols are designed to result in substantial muscular deficits, they may not reflect the fatigue associated with sport-specific demands that have been associated with the increasing incidence of injury as the match progresses. Thus, the aim of this study was to systematically analyze the progressive changes in lower extremity mechanics and performance during an individualized exercise protocol designed to simulate a 90-minute soccer match. Previous match analysis data were used to systematically develop a simulated soccer match exercise protocol that was individualized to the participant's fitness level. Twenty-four National Collegiate Athletic Association Division I soccer players (12 men, 12 women) participated in 2 testing sessions. In the first session, the participants completed the Yo-Yo Intermittent Recovery Test Level 1 to assess their fitness level and determine the 5 submaximal running intensities for their soccer match simulation. In the second test session, progressive changes in the rating of perceived exertion (RPE), lower extremity performance (vertical jump height, sprint speed, and cutting speed), and movement mechanics (jumping vertical stiffness and terminal landing impedance) were measured during the soccer match simulation. The average match simulation running distance was 10,165 ± 1,001 m, consistent with soccer match analysis research. Time-related increases in RPE, and decrements in sprinting, and cutting speed were observed, suggesting that fatigue increased as the simulation progressed. However, there were no time-related decreases in vertical jump height, changes in lower extremity vertical stiffness in jumping, or vertical impedance during landing. Secondary analyses indicated that the coordinative changes responsible for the maintenance of stiffness and impedance differed between the dominant and nondominant limbs. Despite an increase in RPE to near exhaustive levels, and decrements in sprint and cutting performance, the participants were able to maintain jump performance and movement mechanics. Interestingly, the coordinative changes that allowed for the maintenance of vertical stiffness and impedance varied between limbs. Thus, suggesting that unilateral training for performance and injury prevention in soccer-specific populations should be considered.


Subject(s)
Exercise Test/methods , Soccer/physiology , Adolescent , Athletic Performance/physiology , Biomechanical Phenomena/physiology , Female , Humans , Lower Extremity/injuries , Lower Extremity/physiology , Male , Muscle Fatigue/physiology , Physical Fitness/physiology , Running/physiology , Soccer/injuries , Young Adult
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