48760 research outputs found
Sort by
Effect of Hydration Status on Neuromuscular Performance Before and After Intermittent Exercise in the Heat
Full text linkMaintaining optimal fluid balance is essential for athletic performance and recovery, especially during exercise in the heat. However, the effect of dehydration on neuromuscular performance with intermittent exercise remains unknown. PURPOSE: To examine the effect of hydration status on neuromuscular performance before and after intermittent exercise in the heat. METHODS: Eight male soccer players (age, 21±2years; body mass, 75.5±9.1kg; maximal oxygen consumption [VO2max], 65.4±11.8mL·kg-1·min-1) completed a VO2max test to qualify for the study. Following this, they performed a familiarization trial, which included ultrasound (cross-sectional area [CSA], depth), single-leg hop (SLH), and isometric knee extensions (peak torque, peak RTD) with electromyography (EMG) sensors to collect rate of torque development (RTD30, RTD50, RTD100, RTD200), peak EMG, and electrical mechanical delay (EMD). Then, participants completed the familiarization trial with a 45-minute intermittent exercise in the heat (33ºC, 30% relative humidity). Experimental trials included the same protocol of pre- and post-neuromuscular testing, and a soccer simulated intermittent exercise (two bouts of 45-minutes with a 15-minute break in between) that consisted of sprinting, jogging, walking, and standing. The exercise intensity was individualized based on the participant’s VO2max. During all trials, heart rate (HR) and rectal temperature (TREC) were measured. Two experimental (euhydrated [EUH] or dehydrated [DEH]) trials were randomly assigned; DEH, participants completed a 24-hour fluid restriction prior to the trial and 300 mL of water was provided during the break; EUH, participants started the exercise with a euhydrated state and were prescribed fluid to maintain it. Before and after exercise, urine specific gravity (USG), urine osmolality (UOSM), and body mass loss (BML) were measured. RESULTS: CSA and depth were greater in EUH (mean±standard error; 14.2±1.0mm2, 2.40±0.09mm) compared to DEH (13.4±0.9mm2, 2.27±0.08mm, p\u3c0.05). SLH was greater in EUH post values (138±8cm) than DEH post (133±8cm, p\u3c0.05). Peak torque, peak RTD, RTD 200, and peak EMG were not different between EUH and DEH (p\u3e0.05). Although, RTD30, RTD50, and RTD100 with EUH (457±64Nm·s-1, 624±102Nm·s-1, 870±143Nm·s-1) were greater than DEH (369±48Nm·s-1, 500±69Nm·s-1, 748±100Nm·s-1, p\u3c0.05), respectively. EMD was lower in EUH (90.6±6.1ms) than DEH (98.2±6.4ms, p\u3c0.05). Average HR and TREC during exercise were lower in EUH (139±9bpm, 37.93±0.22ºC) than DEH (148±10bpm, 38.42±0.29ºC, p\u3c0.05). USG, UOSM, and BML were lower in EUH (1.006±0.002, 232±42mmol·kg-1, 0.33±0.52%) than DEH (1.025±0.001, 947±29mmol·kg-1, 6.07±1.58%, p\u3c0.05). CONCLUSION: Dehydration can negatively impact neuromuscular performance and injury risk along with thermoregulatory and cardiovascular strain during exercise in the heat
Voluntary Wheel Running Improves Glucose Homeostasis and Visceral Adiposity in Old Mice
Full text linkAge is an independent risk factor for the development of type 2 diabetes, which is characterized in part by impaired glucose homeostasis, greater body weight and visceral adiposity. In older humans, exercise has been demonstrated to be a viable modality to improve these aforementioned outcomes. Surprisingly, to date, no one has assessed whether exercise improves glucose tolerance in old mice. Further the mechanism(s) of improvement in old animals independent of overt obesity is not well understood. PURPOSE: The purpose of this study was to determine whether 8 weeks of voluntary wheel running would result in improved glucose tolerance and shed light on the potential target tissues, such as the visceral adipose, liver, and/or skeletal muscle that are mechanistically responsible for improvements in glucose homeostasis. METHODS: Old (22-24mo) male C57BL6 mice were randomly selected to undergo 8 weeks of voluntary wheel running (n=13-25) or remain sedentary (n=13-15). The day prior to and following 8 weeks of voluntary wheel running, mice underwent a glucose tolerance test (GTT), which was assessed by i.p. injection of glucose (2g/kg). Blood glucose was measured over 120min using a handheld glucometer. Following euthanasia, the liver, perigonadal visceral adipose tissue (WAT), and quadriceps muscles were dissected and weighed. Differences were assessed by either an independent samples t-test or a simple linear regression. Data expressed as mean±SEM. RESULTS: Mice ran an average of 679.0±134.1 m/day. Mice which ran less than 100m/day were excluded from analysis. Δ(change from pre-post) area under the curve analysis of the GTT revealed that voluntary wheel running resulted in substantial improvements in glucose tolerance (Units Arbitrary (AU); Control: 1047±2037AU, Exercise -6305±1841AU; p=0.0061) and ΔBody weight (Control: 0.9067±0.5192g, Exercise:-3.893±0.5757g; p=0.0003) compared to controls. Interestingly, we observed that exercise only led to a reduction in WAT (Control: 0.7982±0.1346g, Exercise:0.4865±0.08099g; p=0.02) weight, but no differences in the weight of the liver (Control:2.032±0.1357g, Exercise:1.867±0.07141g; p=0.1293) or quadriceps (Control: 0.3311±0.01299g, Exercise: 0.3397±0.01265g; p=0.31). We then sought to determine which of these outcomes (i.e. body weight, tissue weight) was most closely related with glucose tolerance. We correlated body weight, WAT weight, liver weight, and quad weight with post GTT area under the curve. We found that body weight (R2=0.16, p=0.02) and WAT weight (R2=0.26, p=0.0065) were most closely associated with glucose tolerance. Whereas liver (R2=0.001; p=0.84) and surprisingly quad weight (R2=0.05; p=0.25) were not related to AUC. CONCLUSION: Our results are the first to demonstrate that exercise is sufficient to induce improvements in glucose tolerance in old mice. Further, these changes appear to be mostly driven by visceral adiposity and are independent of changes in lean mass and liver weight. Thus, highlighting visceral adipose as a target tissue to further study the mechanism(s) by which exercise improves glucose homeostasis in aging
Validity of a Hydration Assessment Device for Determination of Hydration Status
Full text linkEuhydration, defined as the state of optimal total body water content, is essential for maintaining proper physiological function across multiple systems and organs. However, there is currently a lack of assessment that can provide a rapid, non-invasive and cost-effective diagnosis of hydration status. PURPOSE: To evaluate the validity of the commercial accessible hydration sensor in determining hydration status compared to urine and blood indices. METHODS: Twenty-eight participants (age: 23 ± 3 yr; body mass: 73.38 ± 17.03 kg; height: 169.90 ± 9.07 cm) completed this study. Twenty participants performed the first experimental design, whereas eight participants performed the second protocol. In the first protocol, participants arrived to the laboratory in a euhydrated state (urine specific gravity [USG] \u3c 1.020) and performed baseline measures (blood sample, urine sample, and hydration device reading). Then, a dehydrating exercise protocol in the heat (33°C, 30% relative humidity) was performed which involved two 30-min cycling sets separated by a small rest period. Following this, a 2-hr rehydration protocol via fluid consumption was carried out. Outcome measures were collected during the rest period of the exercise, and at the 1- and 2-hr timepoints during the rehydration protocol. In the second experimental design, a similar approach to the first protocol was performed. However, the dehydrating exercise involved cycles of running in the heat until ≥ 2% body mass loss (BML) was obtained. Receiver operating characteristics analysis was performed to calculate sensitivity (SENS) and specificity (SPEC) of the total score from the hydration device in detecting a dehydrated or euhydrated state compared to urine and blood hydration indices. A hydration device total score \u3e 0 indicated euhydrated, while \u3c 0 indicated dehydrated. When comparing the hydration device to urine and blood indices, the following cut-off points were used to determine dehydration: USG ≥ 1.020, urine osmolality (UOSM) \u3e 700 mOsmol, and plasma osmolality (POSM) \u3e 290 mOsmol. RESULTS: The hydration device total score resulted in low to moderate SENS and SPEC for USG (SENS: 0.656; SPEC: 0.000), UOSM (SENS: 0.667; SPEC: 0.250), and POSM (SENS: 0.679; SPEC: 0.286). CONCLUSION: These findings suggest that the hydration device is not accurate for determining euhydration or dehydration when compared to typical urine and blood hydration markers
Rapid Onset Pressor Response in Young Healthy Hispanic Adults
Full text linkHispanic population is the fastest growing ethnic group in the U.S. and experiences a high prevalence of hypertension, a key risk factor of cardiovascular disease. Alterations in the regulation of blood pressure at the onset of exercise are evident in adults with hypertension and those with family history of hypertension. However, it is currently unknown whether such maladaptive pressor responses manifest during acute exercise in young Hispanic adults free from overt cardiovascular disease. PURPOSE: In this study, we examined the blood pressure response at the onset of static handgrip exercise in 19 Hispanic/Latino (H/La; 7 women) and 18 non-Hispanic White (NHW; 6 women) adults matched for age (H/La = 20 ± 2 (mean ± SD), NHW = 22 ± 4 years, p = 0.14) and BMI (H/La = 25 ± 2, NHW = 23 ± 3 kg/m2, p = 0.12). METHODS: Heart rate (HR; lead II ECG) and blood pressure (finometer) were measured during first 30 seconds of isometric handgrip (IHG) exercise at 30% and 40% of maximum voluntary contraction (MVC) and averaged for every 10 seconds. Stroke volume was calculated using modelflow technique and multiplied by HR to acquire cardiac output (CO). Total vascular conductance (TVC) was calculated as mean arterial pressure (MAP)/CO. RESULTS: Baseline MAP was similar between groups (H/La = 80 ± 6, NHW = 82 ± 8 mmHg, p = 0.31) however, the increase in MAP during IHG was significantly higher in Hispanic adults at both 20 seconds (30% MVC: H/La = 8 ± 4, NHW = 4 ± 4 mmHg, p = 0.01; 40% MVC: H/La = 10 ± 5, NHW = 5 ± 5 mmHg, p = 0.03) and 30 seconds (30% MVC: H/La = 10 ± 5, NHW = 5 ± 5 mmHg, p = 0.01; 40% MVC: H/La = 13 ± 7, NHW = 8 ± 5 mmHg, p = 0.03) of graded IHG exercise. This was accompanied with significantly higher decrease in TVC in Hispanic adults during first 20 seconds (30% MVC: H/La = -1 ± 5, NHW = 9 ± 9 ml/min/mmHg, p = 0.001; 40% MVC: H/La = 6 ± 8, NHW = 19 ± 19 ml/min/mmHg, p = 0.01) and 30 seconds (30% MVC: H/La = -1 ± 8, NHW = 11 ± 11 ml/min/mmHg, p = 0.002; 40% MVC: H/La = 6 ± 9, NHW = 18 ± 19 ml/min/mmHg, p = 0.02), indicating greater peripheral vasoconstriction in H/La adults during onset of IHG exercise at both intensities. The increase in HR (10-s: p=0.02; 20-s: p = 0.01) and CO (10-s: p=0.02; 20-s: p = 0.03) was significantly higher in NHW adults as compared to H/La adults during first 10 and 20 seconds of HG exercise at 40% MVC. CONCLUSION: These data suggest that the young healthy Hispanic adults demonstrate exaggerated pressor response coupled with exaggerated peripheral vasoconstriction at the onset of the exercise
Anthropometric Measures Associated with Orthopedic Injuries in Professional Ballet Performers: New DEXA Screening Criteria?
Full text linkMusculoskeletal injuries are common among professional ballet performers. Although dual-energy x-ray absorptiometry (DEXA) is widely used to assess bone mineral density (BMD) and body composition in athletes, no ballet-specific DEXA injury risk thresholds exist. PURPOSE: 1) To compare anthropometric measures obtained through DEXA scans conducted during annual physical evaluations of professional ballet performers who sustained musculoskeletal injuries with those who did not in the year following their scan; 2) To identify potential population-specific injury risk thresholds relevant to professional ballet performers. We hypothesized that those who experienced injuries (INJ) during a year-long performance season tend to exhibit reduced lean mass, %body fat, and BMD compared to those who did not (NonINJ). METHODS: All procedures for this investigation were approved by the institutional review board. A total of 199 DEXA scans (M=102, 25.33± 5.64yrs, 177.90±5.32cm, 72.07±5.92kg|F=97, 24.46±5.72yrs, 165.03±4.28cm, 51.97±5.30kg) performed on professional ballet dancers from a single dance company taken during yearly physicals between 2017-2022 were retrospectively analyzed. The electronic hospital record was also reviewed for each performer. For those sustaining injuries in the year following their DEXA scan, level of injury, anatomic location, and diagnosis were recorded. Level of injury was defined as: 0=none; 1=musculoskeletal complaints with no alteration to participation; 2= injuries resulting in modification or reduced participation; 3=injuries requiring full removal from participation. Within the males and females respectively, an independent samples T-test was used to compare DEXA measures between those who sustained no injuries (Level 0) compared to any reported injury (Level 1-3) and between those who sustained either no, or only minor injuries (Level 0-1) compared to those sustaining higher level injuries (Level 2-3). Significance was set at
Analyzing Novice’s Free Throw Accuracy In Response to Different Feedback
Full text linkFeedback is an essential component of an athlete’s performance and much research has explored the effect that various forms of feedback have on skill acquisition. For novices, there is speculation on what type of feedback would be more beneficial, especially regarding accuracy. PURPOSE: This study analyzed which form of feedback: visual (ViFB), verbal (VFB), or observational (OFB), yielded better performance in free throw accuracy amongst novices. METHODS: 39 University-aged individuals volunteered and were randomly assigned into one of 3 feedback groups. Participants completed a baseline test, a series of acquisition trials, and a retention test. Specifically, participants shot 15 free throws in the baseline and retention test (3 x 5 shots with a minute break in between) and 25 free throws in the acquisition trials (5 x 6 with a 2-minute break in between) with feedback being administered depending on their group. A scale, graded 0-5 based on where the ball hit the basket, assessed accuracy scores. RESULTS: A 2 (test) x 3 (group) mixed-model ANOVA was conducted to examine improvement within and among the three feedback groups. The results showed a significant difference between baseline and retention tests (p \u3e.05) with a post-hoc analysis concluding that there was improvement from baseline to retention. However, there were no significant differences in the accuracy scores among the feedback groups (p \u3e.05). The test also showed that there was a non-significant test x group interaction (p \u3e.05) but further investigation revealed that OFB improved significantly from the baseline to the retention test (PCONCLUSION: the results of the study suggests the post-hoc analysis of the interaction gives us insight to a potential pattern of improved free throw accuracy within the OFB group. Further research should be conducted to determine the effects of OFB accurately. Some findings within this study align with previous research supporting the use of OFB to introduce novice individuals to a new skill
Preliminary Evidence for the Effects of a Mental Toughness Intervention on Athlete Engagement: A Longitudinal Study in Collegiate Dancers
Full text linkEngagement is an active, work-related positive psychological state characterized by the intensity and direction of cognitive (CE), emotional (EE), and behavioral (BE) energy toward performance, well-being, and resilience outcomes in high-pressure environments. Mental toughness (MT), the capacity to consistently perform under pressure, may help increase engagement. As the professionalization of college athletics advances, athletes increasingly function as employees, requiring full psychological engagement. This study is the first to examine the effectiveness of an MT intervention on athlete engagement. PURPOSE: To examine the effectiveness of an MT intervention on athlete engagement, measured across CE, EE, and BE domains, as well as overall engagement (OE). METHODS: A convenience sample of female collegiate dancers (N = 35) participated in a structured, weekly MT intervention, with engagement assessed weekly at five time points (T1–T5). MT was measured using the Mental Toughness Index, while engagement was assessed using the Employee Engagement Scale. Linear mixed-effects models (LMMs), implemented in Python (v3.10) using Statsmodels (v0.14), accounted for within-subject correlations and repeated measures. Separate LMMs were conducted for OE as well as each engagement subscale to examine their unique relationships with MT over time. The models included MT Total, Time, and their interaction as fixed effects, with random intercepts by participant ID. Assumption checks confirmed normality (Shapiro-Wilk p = .006), no autocorrelation (Durbin-Watson = 1.95), and acceptable multicollinearity (VIF \u3c 6). Ordinary Least Squares regressions produced comparable results. Restricted Maximum Likelihood Estimation was used for model fitting. Results were interpreted considering engagement trends and increasing academic and dance-related pressures. The intervention remains ongoing, and all key MT dimensions have not yet been covered. RESULTS: MT significantly predicted higher OE (p = .005, β = 0.340), with the strongest effects observed for BE (p \u3c .001, β = 0.250) and EE (p = .035, β = 0.119). However, CE declined significantly over time (p = .021, β = -2.496), despite the intervention. Additionally, OE exhibited a significant downward trend over time (p \u3c .001, β = -0.690), suggesting external factors may have contributed to this decline. Time did not significantly influence OE (p = .167), and MT × Time interactions were non-significant (p = .499), indicating that the effect of MT on engagement remained stable over time. CONCLUSION: The MT intervention effectively enhanced EE, fostering belonging and commitment to the team, and personal connection to their role. Additionally, BE increased, indicating a greater willingness to exert extra effort contributing to team success. However, OE declined over time, likely due to increasing academic and dance-related demands, despite rising MT levels. CE\u27s decline highlights the need for targeted interventions to maintain focus. Upcoming MT sessions will address additional key variables, such as attention regulation, which may further enhance engagement. Our work serves as an exploratory, hypothesis-generating investigation, laying the foundation for future research on MT-driven engagement interventions in sports and other high-pressure contexts
Potential Immune Health Benefits of Nasal Breathing Exercise on Inflammatory Cytokines in Plasma and Peripheral Blood Mononuclear Cells
Full text linkNasal breathing (NB) is gaining popularity in exercise routines to enhance performance and overall health. However, its effects on intracellular and extracellular inflammatory cytokines, which are crucial to the immune response, remain unclear. PURPOSE: This study examined the acute responses of pro- and anti-inflammatory cytokines in peripheral blood mononuclear cells (PBMCs – representing intracellular cytokines) and plasma (representing extracellular cytokines) following maximal aerobic exercise with NB. METHODS: Eleven physically healthy, sedentary men (age = 20.63±1.36, BMI=26.03±3.16 kg/m2, and VO2max = 32.60±6.46 mL/kg/min) were randomly assigned to either the NB (N=6) or the combined (control) breathing (CB, N=5) group. Both groups performed maximal aerobic exercise on a recumbent bike. Blood samples were collected in EDTA-containing vacutainer tubes before and immediately after maximal exercise to assess changes in pro- (IL-6 and IL-1β) and anti-inflammatory cytokines (IL-10) in plasma and PBMCs. PBMCs were isolated using density gradient centrifugation over Lymphoprep. RESULTS: The concentrations of intracellular cytokines were significantly lower than those of extracellular cytokines. For instance, the intracellular IL-6 was 1.92±1.55 pg/mL, while the extracellular IL-6 was 10.10±9.3 pg/mL (p=0.001). The intracellular IL-10 (2.55±1.41 pg/mL) was 7 times lower than the extracellular IL-10 (18.18±17.66 pg/mL, p=0.008), and the intracellular IL-1β was 0.80±0.82 pg/mL, whereas the extracellular IL-1β was 17.73±16.77 pg/mL (p=0.004). Although no differences were observed in IL-10 and IL-1β between the NB and CB groups following maximal exercise, the intracellular IL-6 was significantly lower (p=0.029) in the NB (1.24±1.27 pg/mL) than in the CB (2.79 ± 1.5 pg/mL) group. CONCLUSIONS: This study revealed that intracellular cytokine concentrations were lower than extracellular cytokine levels. This discrepancy likely results from the accumulation of secreted cytokines in plasma, derived from multiple cellular and tissue sources, systemic pooling, and the transient presence of cytokines within PBMCs. Additionally, the decrease in intracellular IL-1β levels following exercise with nasal breathing (NB) suggests potential immune health benefits. Further research is necessary to validate and extend these findings across various exercise modalities and diverse populations
Exploring the Relationship Between Physical Activity and Stress Levels Among International Graduate Students
Full text linkIt is not uncommon for individuals to experience significant mental stress at one time or another in their lives. For students, subjective experiences with stressors can result in a low quality of life, impair one\u27s capacity to deal with everyday issues, and eventually have an impact on academic achievement. The acute consequences may lead to cognitive impairment, greater states of loneliness, and higher states of fatigue, while the chronic consequences may include interpersonal dysfunction and persistent problems associated with physical and mental health. PURPOSE: The purpose of the study is to determine the relationship between physical activity and stress levels among international graduate students. METHODS: Twenty-four international graduate students from Midwestern State University were recruited based on specific inclusion and exclusion criteria. Physical activity data was collected using a standardized questionnaire, while stress levels was assessed using the Perceived Stress Scale (PSS). RESULTS: Among the participants, 4 individuals fell into the low-stress category, indicating minimal perceived stress. The majority, 13 participants, experienced moderate stress, suggesting a considerable but manageable level of stress. Additionally, 7 participants were classified under high stress, indicating significant stress levels that may require further attention. A significant difference (p = 0.04) was found when comparing stress scores between participants who exercised and those who did not, suggesting that engaging in exercise may result in lower level of stress. Among individuals who exercised, participants who exercised 3-4 times a week had significantly (p = 0.04) lower reported stress compared to participants who exercised 1-2 times a week. With regard to exercise session duration, no significant relationship (p = 0.078) was observed between stress scores and the duration of exercise sessions among those who exercised. CONCLUSION: These findings suggest that the frequency of physical activity, rather than session duration, plays a crucial role in stress management for international graduate students. Encouraging regular exercise may serve as an effective, non-pharmacological strategy to enhance mental health and academic performance. Future research could further investigate the effects of exercise intensity and type to better understand their impact on stress reduction
Shoe Heel-Toe Drop Affects Running Economy
Full text linkIn distance running, using less metabolic energy at a given speed improves endurance performance. Athletes can decrease their metabolic energy expenditure during running (improve their running economy) by improving their running mechanics. One way to elicit economical running mechanics is to use running shoes with specific characteristics, such as the ideal heel-toe drop. Wearing shoes with a higher heel-toe drop increases ankle plantar flexion, in turn decreasing the operating lengths of the underlying calf muscles. Given that producing force with muscles at shorter operating lengths increases their metabolic energy expenditure, we hypothesized that running in shoes with a higher heel-toe drop would increase user metabolic energy expenditure during running. PURPOSE: Determine how shoe heel-toe drop affects running economy. METHODS: Twenty runners participated (1 female, 19 males; avg ± sd; age: 31.6 ± 10.7 years; height: 1.75 ± 6.3 m; mass: 72.5 ± 8.1 kg). Participants performed a treadmill familiarization trial in their own shoes followed by four 5-minute experimental running trials at 3.5 m/s. In each experimental trial, participants ran in a different custom Nike Pegasus shoe with EVA midsoles that differed in their heel-toe drop: 0, 10, 20, & 30 mm. We randomized shoe conditions and provided at least 5-min seated rest between trials. We computed mass-normalized net metabolic power, biomechanics, and leg muscle activity during running in each shoe condition. RESULTS: Shoe heel-toe drop affected metabolic power (p\u3c0.001). Running in shoes with a 30 mm heel-toe drop increased net metabolic power ~2% compared to the 0 mm heel-toe drop condition. Higher heel-toe drops shortened medial gastrocnemius muscle fascicle length at touch-down, toe-off, and on average during ground contact (p ≤ 0.025). Shoe heel-toe drop did not affect medial gastrocnemius muscle average (p = 0.405) or peak (p = 0.081) muscle fascicle velocity during ground contact. Lateral gastrocnemius muscle activation decreased in the higher heel-toe drop shoes during stance (p = 0.061) and stride (p = 0.067). Alternatively, higher heel toe-drop increased soleus muscle activation during stance (0.314) and stride (p = 0.235). Neither peak nor average muscle activation of the tibialis anterior changed between shoe conditions (both p ≥ 0.184). Higher heel-toe drops decreased the average vertical ground reaction force (p = 0.014) and lengthened ground contact time (p = 0.015) during running. Shoe heel-toe drop did not affect stride frequency (p = 0.682). CONCLUSION: Running in shoes with a lower heel-toe drop enables calf muscles to operate at longer, more economical lengths. Accordingly, shoes with a lower heel-toe drop reduces user metabolic energy expenditure during running, and in turn likely improves their distance-running performance