Evaluation of a wearable fabric-based sensor for accurate sodium determination in sweat during exercise.

INTRODUCTION: Newly developed wearable fabric sensors (WFS) can increase the ease and accuracy of sweat sodium measurements by performing simultaneous sampling and analysis on the body during exercise. PURPOSE: Determine the accuracy of a WFS for measurement of sodium concentration in sweat. METHODS: Subjects wore a WFS prototype and sweat collectors on their forearm during cycle ergometry. Subjects exercised at a moderate intensity (~ 65% heart rate reserve) for 30-60 min. Sweat samples were collected and analyzed using a commercial sweat sodium analyzer (SSA) every 10-15 min. WFS were adhered with an armband and connected to custom built electronics. Accuracy was determined by comparing predicted WFS concentration to the actual concentration from the commercial SSA and analyzed statistically using ANOVA and Bland-Altman plots. RESULTS: A total of 19 subjects completed the study. The average sweat sodium concentration was 59 mM ± 22 mM from a SSA compared with 54 mM ± 22 mM from the WFS. Overall, the average accuracy of the WFS was 88% in comparison to the SSA with p = 0.45. A line of best fit comparing predicted versus actual sweat sodium concentration had a slope of 0.99, intercept of - 4.46, and an r2 of 0.90. Bland-Altman analysis showed the average concentration difference between the WFS and the SSA was 5.35 mM, with 99% of data points between ± 1.96 times the standard deviation. CONCLUSION: The WFS accurately predicted sweat sodium concentration during moderate intensity cycle ergometry. With the need for precise assessment of sodium loss, especially during long duration exercise, this novel analysis method can benefit athletes and coaches. Further research involving longer duration and more intense exercise is warranted.

Differential in Maximal Aerobic Capacity by Sex in Collegiate Endurance Athletes Consuming a Marginally Low Carbohydrate Diet.

PURPOSE: Although current sports nutrition recommendations advocate for a high carbohydrate (CHO) intake among endurance athletes, recent research has suggested that training with low CHO availability may augment adaptations to aerobic training. The purpose of this study was to observe the dietary habits of collegiate distance runners and to investigate the effects of habitual CHO intake on aerobic performance [VO2max(post)] during a competitive season. METHODS: During an 8-week trial period, 12 (N = 12) collegiate track athletes recorded their self-selected dietary intake via 24-hour recall. Analysis of CHO intake was conducted by a registered dietitian. Pre [VO2max (pre)] and post [VO2max (post)] season aerobic capacity assessments were performed using a one-way analysis of covariance (ANCOVA) with 2 covariates controlling for VO2max (pre) and CHO intake compared to the variance in VO2max (pre) and VO2max (post) by sex. RESULTS: The average CHO was 4.11 ± 1.03 g/kg body mass (BM), with only one female athlete meeting dietary recommendations, consuming ≥ 6 g/kg BM. Male distance runners on average had a lower CHO than females. After adjusting for VO2max (pre) and CHO, there were statistically significant differences between VO2max (post) group means by sex with a difference of 12.62 ml/kg/min (95% confidence interval [CI], 2.12-23.12, p = 0.02), with CHO accounting for 18% of the variance in VO2max (post). CONCLUSION: Collegiate distance runners exhibited marked improvements in maximal aerobic capacity during the in-season while consuming a marginally low-CHO diet, with a predominant effect in males. Therefore, CHO intakes below current recommendations for endurance athletes might not be detrimental to aerobic training adaptations.

RMR Estimation Model Accuracy Using Air Displacement Plethysmography-Derived Body Composition Measures in Young Adults.

OBJECTIVE: Predictive equations derived from regression techniques based on large samples are extensively utilized in estimating resting metabolic rate (RMR). Body composition assessments utilize model equations to estimate RMR. However, the agreement of these predictive models with indirect calorimetery (IC) has come into question. Our aim is to investigate the agreement of RMR estimation models using air displacement plethysmography (ADP) measures against a gas exchange IC system (RMR-C). METHODS: Sixty-six participants (25 men, 41 women) completed the study. RMR measurements were obtained from IC and ADP within 10 minutes of one another. IC RMR estimates were tested against 9 other validated models using ADP measures via analysis of variance (ANOVA) techniques with multiple comparisons testing and Bland-Altman analysis. RESULTS: Based on the ANOVA, the Nelson (1992) model underpredicted RMR compared to IC (p < 0.001). The Doré et al. (1982) model was the best predictor of RMR compared to the IC measures (p = 0.907). DISCUSSION: The current RMR estimation model using ADP measures underpredicts total caloric needs. The Doré et al. (1982) model more accurately predicted RMR in the entire sample.

The influence of a Tabata interval training program using an aquatic underwater treadmill on various performance variables.

The purpose of this study was to investigate the effects of an 8-week aquatic treadmill running (ATM) Tabata interval-training program on various performance variables including body fat percentage, force production, flexibility, and anaerobic power. Totally, 25 participants (17 males and 8 females) were randomized into either a control group (CON), which only completed Pre- and Posttesting, or exercise group (EX), which took part in the 8-week ATM Tabata interval-training program. Pre- and Posttesting consisted of the following measurements: body fat percentage, flexibility, force production, and anaerobic power. The Tabata interval-training program consisted of sprinting on an ATM at 7.5 miles⋅h and with the front jets turned on at 80, 85, 90, and 95% progressively increasing throughout the 8 weeks. A 2-way repeated measures analysis of variance revealed a significant effect of time (F = 236.13; p < 0.001) and group by time interaction (F = 1.95; p = 0.02). Paired-samples t-test revealed a significant difference in the CON group from Pre- to Posttesting for mean power from the Wingate test (t = -2.20; p = 0.05) and a significant difference in the EX group for right leg goniometry (t = -2.34; p = 0.04) and mean power from the Wingate test (t = -2.81; p = 0.02). These results are favorable because it demonstrates that participants who engage in an ATM Tabata interval-training program can elicit a strong enough stimulus to improve flexibility and anaerobic power in terms of mean power while decreasing musculoskeletal impact placed on the ligaments, joints, and tendons.

Low-dose caffeine administered in chewing gum does not enhance cycling to exhaustion.

Low-dose caffeine administered in chewing gum does not enhance cycling to exhaustion. The purpose of the current investigation was to examine the effect of low-dose caffeine (CAF) administered in chewing gum at 3 different time points during submaximal cycling exercise to exhaustion. Eight college-aged (26 ± 4 years), physically active (45.5 ± 5.7 ml·kg(-1)·min(-1)) volunteers participated in 4 experimental trials. Two pieces of caffeinated chewing gum (100 mg per piece, total quantity of 200 mg) were administered in a double-blind manner at 1 of 3 time points (-35, -5, and +15 minutes) with placebo at the other 2 points and at all 3 points in the control trial. The participants cycled at 85% of maximal oxygen consumption until volitional fatigue and time to exhaustion (TTE) were recorded in minutes. Venous blood samples were obtained at -40, -10, and immediately postexercise and analyzed for serum-free fatty acid and plasma catecholamine concentrations. Oxygen consumption, respiratory exchange ratio, heart rate, glucose, lactate, ratings of perceived exertion, and perceived leg pain measures were obtained at baseline and every 10 minutes during cycling. The results showed that there were no significant differences between the trials for any of the parameters measured including TTE. These findings suggest that low-dose CAF administered in chewing gum has no effect on TTE during cycling in recreational athletes and is, therefore, not recommended.

The effects of high- and low-dose aspirin on thermoregulation during and after acute cold exposure.

OBJECTIVE: To explore the effect of aspirin on the thermoregulatory responses of men during exposure to 12°C air (acute cold exposure) for a period of 120 minutes and recovery in 25°C air (rewarming) for 120 minutes. METHODS: Seven male subjects (26.1 ± 2.4 yr) underwent pre-experimental testing to determine peak VO(2) and body composition. Participants underwent 3 trials in which they ingested the following for 1 week prior to each experimental trial: a capsule filled with cellulose (placebo), 81 mg · day(-1) of aspirin (low-dose aspirin), or 650 mg · day(-1) of aspirin (high-dose aspirin). Each trial consisted of a 30-minute baseline period, 120 minutes of exposure to 12°C air, and 120 minutes of recovery in 25°C air. Mean skin temperature and rectal temperature (T(re)) were measured, and heat production was calculated. RESULTS: During both acute cold exposure and rewarming, analysis of variance revealed a main effect for time (P < .05) with respect to T(re), mean skin temperature, and heat production. However, there were no significant differences between the treatments or treatment by time interactions. CONCLUSIONS: These data demonstrate that aspirin had no significant effect on the thermal and metabolic responses during acute cold exposure and rewarming.

College students' perceptions and experiences with health insurance.

OBJECTIVES: Most research on perceptions of health insurance has examined gender- and race-based differences across sections of the adult population. This is the first study to examine differences based on demographic characteristics of undergraduate college students' coverage and perceptions of health insurance. METHODS: The participants were undergraduates at 12 of the 13 public universities in Ohio. Valid and reliable 40-item questionnaires (n = 1800) were equally distributed to faculty at 12 public universities. RESULTS: A total of 1367 (70%) surveys were completed. Most students (59.9%) believed that the federal government should have the primary responsibility to ensure that Americans have health insurance and 53.3% felt that the best way was through universal health insurance from the federal government. Perceptions varied by race, political affiliation, and health insurance status. CONCLUSIONS: Undergraduate students appear to have formed opinions about health insurance similar to general adult populations. These perceptions may have been obtained by transfer of perceptions from family and friends. A more formalized undergraduate education approach to educating future leaders of society regarding health insurance should be considered. Policy changes to reduce disparities in health status among groups of college students must be explored.

Catecholamine levels in hypoxia-lnduced acute mountain sickness.

UNLABELLED: Enhanced sympathoadrenal activity has been implicated in the pathogenesis of acute mountain sickness (AMS). This study was designed to examine the time course of circulating catecholamines in individuals with and without AMS. METHODS: Subjects were low-altitude residents (10 men, 8 women) who had not been exposed to altitude within the previous 2 mo. They breathed 12% O2 (hypoxia equivalent to 4600 m altitude) for 8 h while seated at rest. AMS was evaluated using Lake Louise scores (LLS) at 0, 1, 3, 5, and 7 h of exposure using a threshold of 3 to define AMS. Blood samples were collected to measure arterial blood gases and oxygen saturation as well as arterial and venous epinephrine (A-EPI and V-EPI) and norepinephrine (A-NE and V-NE). RESULTS: Eight subjects (44%) developed AMS at some time during the experiment. Blood gases showed no significant difference between subjects with or without symptoms (AMS+ and AMS-, respectively). However, AMS+ subjects showed significantly greater concentrations of A-EPI over the 8 h without any between-group difference in V-EPI. Levels of A-NE were significantly higher at baseline and during the first hour of hypoxia in subjects who later developed AMS. V-NE increased significantly over time among all participants with no difference between groups. CONCLUSIONS: These findings suggest a possible physiological marker for individuals who may be relatively susceptible to AMS and provide additional insight into the sympathoadrenal response to acute hypoxia.

A comparison of dual-energy X-ray absorptiometry, air displacement plethysmography and A-mode ultrasound to assess body composition in college-age adults.

BACKGROUND: There is currently a dearth of scientific literature exploring the agreement of A-mode ultrasound (US) body composition analysis with dual-energy X-ray absorptiometry (DXA) and air displacement plethysmography (ADP). OBJECTIVE: To investigate the agreement of US with DXA and ADP for estimating fat mass (FM) and fat-free mass (FFM). METHODS: College-age men (n = 33) and women (n = 41) volunteered to participate in this study. Participants were instructed to adhere to the following pretest protocol: refrain from food and drink 12 h prior to testing and wear tight fitting clothing. Body composition (BCA) was assessed using US, DXA and ADP in accordance with the respective manufacturer's guidelines. Two-way mixed-model AVOVA and Bland and Altman techniques were applied to explore agreement for FM and FFM among the three methods: US, ADP and DXA and by sex. RESULTS: There was no statistically significant effect by sex for either FM or FFM across all BCA comparisons (P = 0·504 and 0·510, respectively). US was not statistically different from ADP for FM and FFM (P ≈ 1·00). However, for FM and FFM, there were significant differences between DXA and both US and ADP (P≤0·001). The Bland and Altman analyses revealed large individual differences for all BCA. CONCLUSION: There was statistical agreement between US and ADP for FM and FFM but lack of agreement for US and ADP when compared to DXA. However, the large limits of agreement between methods warrant caution in generalizing these findings.

Seven-site versus three-site method of body composition using BodyMetrix ultrasound compared to dual-energy X-ray absorptiometry.

Obesity is a steadily growing epidemic affecting all segments of the population including college-aged students. The weight gain that is evidenced amid the transitional stage of college years increases the risks associated with cardiovascular and metabolic diseases. The BodyMetrix® BX-2000 (ULTRA) using a seven-site method has been evaluated against dual-energy X-ray absorptiometry (DXA) for estimation of body composition, which has yielded conflicting results. To date, no studies have compared the three-site method Jackson and Pollock three-site method to DXA. PURPOSE: The purpose of the study was twofold (i) to compare agreement between Jackson-Pollock seven site (JP7), Jackson-Pollock three site (JP3) and Pollock three site (P3) to predict body fat (%BF) using ULTRA and (ii) and to compare the three ULTRA methodologies against DXA. METHODS: Seventy-six healthy college-aged subjects (ages = 22·08 ± 2·50 years) participated in this study. DXA and ULTRA body composition assessments were performed following manufacturer's instructions to estimate %BF. Paired sample t-tests were used to assess agreement between JP7, P3 and JP3. Additionally, a two-tailed sample t-test was performed by sex. ULTRA and DXA results were also performed for agreement and bivariate correlation. RESULTS: No significant differences between JP7 and P3, P = 0·38, were observed. In males, no significant differences were observed between JP7 and P3, P = 0·18. Significant differences were observed in all other pairs, P≤0·001 and between ULTRA and DXA. CONCLUSIONS: The Pollock 3-site method estimates body fat percentage with comparable accuracy to JP7 using ULTRA.

Comparison of air-displacement plethysmography results using predicted and measured lung volumes over a protracted period of time.

BACKGROUND: Air-displacement plethysmography (ADP) systems can either measure or predict lung volume (LV) in their test trials. The repeatability of the predicted and the measured value is an important factor in the accuracy of the final test result. OBJECTIVE: Compare the variability and accuracy of ADP tests using predicted and measured LV over a protracted period of time. METHODS: Twenty-four adults (18-30 years) participated in the study. Each subject underwent three ADP tests over a period of 3 weeks, with 1 week between tests. At each testing session, subjects were tested using a predicted LV protocol and a measured LV protocol in random order. LV, body volume (BV) and per cent body fat (% BF) were compared between testing modes and between assessment times. RESULTS: A two-way ANOVA examined the effect of the mode of LV assessment (measured or predicted) and trial (week) for LV and BV and the effect of the LV mode assessment (measured or predicted) and trial (week) on % BF results. LV and BV did not differ significantly (P>0.05) between the two modes of assessment (measured or predicted). Time (day of assessment) also was not significantly different between trials (P>0.05). Neither mode nor trial was significant (P>0.05), therefore neither had an effect on the % BF results. CONCLUSION: In this investigation, the method used to determine LV during ADP testing did not significantly affect the final % BF result. Also, tests performed over an extended period of time was not affected by LV measurement method.

The rate of absorption and relative bioavailability of caffeine administered in chewing gum versus capsules to normal healthy volunteers.

OBJECTIVE: The purpose of this study was to evaluate the rate of absorption and relative bioavailability of caffeine from a Stay Alert chewing gum and capsule formulation. METHODS: This was a double blind, parallel, randomized, seven treatment study. The treatment groups were: 50, 100, and 200 mg gum, 50, 100, and 200 mg capsule, and a placebo. Subjects consisted of 84 (n=12 per group); healthy, non-smoking, males who had abstained from caffeine ingestion for at least 20 h prior to dosing and were randomly assigned to the treatment groups. Blood samples were collected pre-dose and at 5, 15, 25, 35, 45, 55, 65, 90 min and 2, 3, 4, 6, 8, 12, 16 and 29 h post administration. Plasma caffeine levels were analyzed by a validated UV-HPLC method. RESULTS: Mean Tmax for the gum groups ranged from 44.2 to 80.4 min as compared with 84.0-120.0 min for the capsule groups. The Tmax, for the pooled data was significantly lower (P<0.05) for the gum groups as compared with the capsule groups. Differences in Tmax were significant for the 200 mg capsule versus 200 mg gum (P<0.05). The mean ka values for the gum group ranged from 3.21 to 3.96 h-1 and for the capsule groups ranged from 1.29 to 2.36 h-1. Relative bioavailability of the gum formulation after the 50, 100 and 200 mg dose was 64, 74 and 77%, respectively. When normalized to the total drug released from the gum (85%), the relative bioavailability of the 50, 100 and 200 mg dose were 75, 87, and 90%, respectively. No statistical differences were found for Cmax and AUCinf for comparisons of the gum and capsule formulations at each dose. Within each dose level, there were no significant formulation related differences in Cmax. No significant differences were observed in the elimination of caffeine after the gum or capsule. CONCLUSIONS: The results suggest that the rate of drug absorption from the gum formulation was significantly faster and may indicate absorption via the buccal mucosa. In addition, for the 100 and 200 mg groups, the gum and capsule formulations provide near comparable amounts of caffeine to the systemic circulation. These findings suggest that there may be an earlier onset of pharmacological effects of caffeine delivered as the gum formulation, which is advantageous in situations where the rapid reversal of alertness and performance deficits resulting from sleep loss is desirable.

Age effects on thermal, metabolic, and perceptual responses to acute cold exposure.

INTRODUCTION: Thermoregulatory accidents rank as the sixth leading cause of death among older adults. Therefore, there is an urgency to clarify the influence of age on thermoregulation. This investigation sought to evaluate the influence of age on the thermal, metabolic, and perceptual responses of healthy, physically active, old (OLD) and young (YNG) men during exposure to 12, 18, and 27 degrees C for 120 min. METHODS: There were four old (67.7 +/- 4.6 yr) and four young (26.7 +/- 3.4 yr) adult men who participated. Following a baseline period (30 min), the subjects, wearing only cotton shorts, were moved into an environmental chamber where they remained seated for 120 min or until rectal temperature (Tre) was < or = 35 degrees C. Data were collected for Tre, mean skin temperature (Tsk), oxygen consumption (Vo2), tissue insulation (I), thermal sensation (TS), and heat production (HP). RESULTS: Analysis of variance demonstrated a significant (p < 0.05) time x group interaction for Tre, HP, and I, whereby Tre, HP and I were higher in the YNG vs. OLD. Also, Tsk differed between YNG and OLD with the OLD exhibiting a higher Tsk. TS did not differ, although subjects reported feeling colder with each trial. DISCUSSION: These data suggest that there may be a differential thermoregulatory response between OLD and YNG individuals. The higher Tsk in the OLD suggests a deficit in the peripheral response leading to an increased heat loss over a protracted period of time. This heat loss may contribute to the reduction in core temperature and to the development of hypothermia in the older adult.

Agreement between ultrasound and dual-energy X-ray absorptiometry in assessing percentage body fat in college-aged adults.

BACKGROUND: The BodyMetrix(®) BX-2000 Ultrasound device (ULTRA) shows prowess in being an effective alternative to the expense and technicality of dual-energy X-ray absorptiometry (DXA). However, this technique has not been investigated using a seven-site methodology. SUBJECT/OBJECTIVE: To employ a cross-over design to investigate the agreement between ULTRA using a seven-site methodology and DXA in assessing body fat (%BF) in a normal-weight sample of college-age men and women. METHODS: Subjects (n = 84, BMI = 23.6 ± 3.6 kg m(-²), age = 23.0 ± 4.7 years) participated in this study with %BF measurements following the manufacturer's specifications. RESULTS: Significant differences were observed between methods with ULTRA less than DXA (difference = 4.4 ± 0.8%, t-statistic = 7.27, P<0.001) with no difference between men and women. CONCLUSION: The current study showed that ULTRA using a seven-site methodology did not agree with DXA in measuring %BF. Thus, this investigational ULTRA methodology might not be appropriate in estimating %BF in this population.

Validity of Borg Ratings of Perceived Exertion During Active Video Game Play.

During physically interactive video game play (e.g., Nintendo Wii), users are exposed to potential distracters (e.g., video, music), which may decrease their ratings of perceived exertion (RPE) throughout game play. The purpose of this investigation was to determine the association between RPE scores and heart rate while playing the Nintendo Wii. Healthy adults (N = 13, 53.5 ± 5.4 years old) participated in two exercise sessions using the Nintendo Wii Fit Plus. During each session participants played a five-minute warm-up game (Basic Run), two separate Wii Fit Plus games (Yoga, Strength Training, Aerobics or Balance Training) for fifteen minutes each, and then a five-minute cool down game (Basic Run). Borg RPE and heart rate were assessed during the final 30 seconds of the warm up and cool down, as well during the final 30 seconds of play for each Wii Fit Plus game. Correlation analysis combining data from both exercise sessions indicated a moderate positive relationship between heart rate and RPE (r = 0.32). Mixed-effects model regression analyses demonstrated that RPE scores were significantly associated with heart rate (p < 0.001). The average percentage of age-predicted heart rate maximum achieved (58 ± 6%) was significantly greater (p = 0.001) than the percentage of maximum RPE indicated (43 ± 11%). Borg RPE scores were positively associated with heart rate in adults during exercise sessions using the Wii Fit Plus. However, this relationship was lower than observed in past research assessing RPE validity during different modes of exercise (e.g. walking, running) without distracters.

The effects of nicotine on the metabolic and hormonal responses during acute cold exposure.

OBJECTIVE: To examine the effects of nicotine on the metabolic and hormonal responses during acute cold exposure. METHODS: Participants in this study included 6 men and 5 women between the ages of 19 and 25 years. Each subject performed 2 cold-air trials (CATs) consisting of a 30-minute baseline (BASE) period and a 120-minute exposure to 10 degree C air. One CAT was performed after a nicotine (NIC) dosing using a 21-mg transdermal patch, whereas the other CAT was performed after a placebo (PL) treatment. Blood samples for metabolic and hormonal measurements were obtained at the end of BASE and immediately after the cold exposure. RESULTS: When examining the sexes separately, there was no difference in norepinephrine between PL and NIC (P = .066). There was also no difference in epinephrine between PL and NIC in either sex (P = .634). From BASE to 120 minutes of the CAT, there was a significant decrease in cortisol (P = .036), but this response was similar between the 2 treatments (P = .077). Glucose and glycerol concentrations were not different between the PL and NIC treatments. At BASE, nonesterified fatty acid (NEFA) concentration was lower during PL compared with NIC (P = .021); however, at 120 minutes of the CAT, NEFA was greater during PL compared with NIC (P = .035). CONCLUSIONS: During 120 minutes of cold exposure, NIC resulted in alterations in the responses in NEFA, whereas the other blood measurements were not significantly different between the 2 groups.

The effect of cold exposure on the hormonal and metabolic responses to sleep deprivation.

OBJECTIVE: The purpose of this study was to determine the effect of 12 degrees C cold exposure for 180-minutes on the hormonal responses of sleep-deprived individuals. METHODS: Participants underwent 2 cold-air trials: 1 after a normal night of sleep (ie, 6-8 hours) and 1 after 33 hours of sleep deprivation (SDEP). A venous blood sample was taken at baseline and then at 90-and 180-minute cold-exposure time points. Repeated-measures analysis of variance was used to determine significance between a normal night of sleep and SDEP for norepinephrine, epinephrine, cortisol, insulin, thyroid hormones triiodothyronine and thyroxine, glucose, and non-esterifled fatty acids. RESULTS: There was no significant main effect for time, trial, or interaction for insulin, thyroid hormones, epinephrine, cortisol, and glucose (P < or = .05). A significant main effect for time for norepinephrine and non-esterified fatty acids was demonstrated (P < .001). DISCUSSION: The lack of significant differences in the hormonal and metabolic responses to cold exposure combined with SDEP may have been because of an ability of the individual to continue to respond despite the environmental stressor or the physiological effect elicited from cold exposure, thereby possibly masking physiological responses of SDEP. CONCLUSIONS: On the basis of these data, SDEP combined with protracted cold exposure apparently was not a great enough stressor to cause a differential response in the hormonal and metabolic parameters.