Limitations associated with thermoregulation and cardiovascular research assessing laborers performing work in the heat.

PURPOSE: To quantify the current literature and limitations associated with research examining thermoregulatory and cardiovascular strain in laborers working in the heat. METHODS: PubMed, SCOPUS, and SPORTDiscus were searched for terms related to the cardiovascular system, heat stress, and physical work. Qualifying studies included adult participants (18-65 years old), a labor-intensive environment or exercise protocol simulating a labor environment, a minimum duration of 120 min of physical work, and environmental heat stress (ambient temperature ≥26.0°C and ≥30% relative humidity). Studies included at least one of the following outcomes: pre- and peak physical work, core temperature, heart rate (HR), systolic blood pressure, diastolic blood pressure, HR variability, and rate pressure product. RESULTS: Twenty-one out of 1559 potential studies qualified from our search. There was a total of 598 participants (mean = 28 ± 50 participants per study, range = 4-238 participants per study), which included 51 females (8.5%) and 547 males (91.5%). Of the participants, 3.8% had cardiovascular risk factors (diabetes: n = 10; hypertension: n = 13) and 96.2% were characterized as "healthy". Fifty-seven percent of the included studies were performed in a laboratory setting. CONCLUSIONS: Studies were predominantly in men (91.5%), laboratory settings (57%), and "healthy" individuals (96.2%). To advance equity in protection against occupational heat stress and better inform future heat safety recommendations to protect all workers, future studies must focus on addressing these limitations. Employers, supervisors, and other safety stakeholders should consider these limitations while implementing current heat safety recommendations.

The validation of contemporary body composition methods in various races and ethnicities.

Few investigations have evaluated the validity of current body composition technology among racially and ethnically diverse populations. This study assessed the validity of common body composition methods in a multi-ethnic sample stratified by race and ethnicity. One hundred and ten individuals (55 % female, age: 26·5 (sd 6·9) years) identifying as Asian, African American/Black, Caucasian/White, Hispanic, Multi-racial and Native American were enrolled. Seven body composition models (dual-energy X-ray absorptiometry (DXA), air displacement plethysmography (ADP), two bioelectrical impedance devices (BIS, IB) and three multi-compartment models) were evaluated against a four-compartment criterion model by assessing total error (TE) and standard error of the estimate. For the total sample, measures of % fat and fat-free mass (FFM) from multi-compartment models were all excellent to ideal (% fat: TE = 0·94-2·37 %; FFM: TE = 0·72-1·78 kg) compared with the criterion. % fat measures were very good to excellent for DXA, ADP and IB (TE = 2·52-2·89 %) and fairly good for BIS (TE = 4·12 %). For FFM, single device estimates were good (BIS; TE = 3·12 kg) to ideal (DXA, ADP, IB; TE = 1·21-2·15 kg). Results did not vary meaningfully between each race and ethnicity, except BIS was not valid for African American/Black, Caucasian/White and Multi-racial participants for % fat (TE = 4·3-4·9 %). The multi-compartment models evaluated can be utilised in a multi-ethnic sample and in each individual race and ethnicity to obtain highly valid results for % fat and FFM. Estimates from DXA, ADP and IB were also valid. The BIS may demonstrate greater TE for all racial and ethnic cohorts and results should be interpreted cautiously.

Effects of adiposity and body composition on adjusted resting energy expenditure in women.

OBJECTIVES: Fat-free mass (FFM) accounts for ~80% of the variance in resting energy expenditure (REE), and this relationship is complicated by adiposity. The objective was to compare adjusted REE and contributions of skeletal lean mass and fat mass (FM) to adjusted REE in women with varying adiposity levels using a novel approach. METHODS: Women were divided into tertiles by body fat percent (%fat): Tertile 1 (T1): %fat = 18.5%-28.4%; Tertile 2 (T2): %fat = 28.5%-33.8%; Tertile 3 (T3): %fat = 34.0%-61.0%. Outcome measures were measured and adjusted REE, body composition (skeletal lean mass, FM, %fat) from dual-energy X-ray absorptiometry, and percent contribution of skeletal lean mass and FM to adjusted REE. RESULTS: The main effect for tertiles (T1 vs. T2 vs. T3) was significant (p = .001); REE was significantly higher in T3 versus both T1 by 281 kcal/day (p = .001) and T2 by 215 kcal/day (p = .001). Expenditure from skeletal lean mass in T1 was significantly higher than T3 by 3.2% (p = .001). T3 had a significantly higher FM contribution than T1 by 5.1% (p = .001) and T2 by 3.9% (p = .001). CONCLUSIONS: Women with elevated %fat experienced lower skeletal lean mass contribution and higher FM contribution to adjusted REE. FM may explain more of the variance in REE between women of different levels of adiposity.

Abdominal Adiposity in Collegiate Football Linemen: A Study of Race and Position.

American football linemen are at an increased risk for developing obesity-related diseases. This study evaluated the impact of race and position on abdominal fat (visceral adipose tissue and android fat percentage) in football linemen. Thirty-four offensive and defensive linemen (%fat: 27.1±7.2%) completed a total body dual-energy X-ray absorptiometry scan to estimate visceral fat and android fat percentage. Participants were stratified by race [Black: n=23; White: n=11] and position (Offense: n=18; Defense: n=16). Two separate two-way ANOVA tests [race × position] were completed. For visceral adipose tissue, there was no interaction (p=0.056), but there was an effect of race (Black: 0.57±0.34 kg; White: 1.51±0.56 kg; p <0.001) and position (Offense: 1.22±0.60 kg; Defense: 0.49±0.34 kg; p<0.001). For android fat percentage, there was no interaction (p=0.855) or race effect (Black: 31.5±11.3%; White: 40.9±8.6%; p=0.123); there was a position effect (Offense: 42.1±5.6%; Defense: 26.0±9.9%; p<0.001). Offensive linemen, regardless of race, had greater visceral adipose tissue and android fat percent compared to defensive linemen. White linemen had greater visceral adipose tissue, regardless of position. These results suggest football linemen, especially offensive linemen with increased abdominal adiposity, may benefit from tracking metabolic health during their collegiate career to mitigate obesity-related disease risk once retired from sport.

Acute feeding has minimal effect on the validity of body composition and metabolic measures: dual-energy X-ray absorptiometry and a multi-compartment model.

Understanding the effects of acute feeding on body composition and metabolic measures is essential to the translational component and practical application of measurement and clinical use. To investigate the influence of acute feeding on the validity of dual-energy X-ray absorptiometry (DXA), a four-compartment model (4C) and indirect calorimetry metabolic outcomes, thirty-nine healthy young adults (n 19 females; age: 21·8 (sd 3·1) years, weight; 71·5 (sd 10·0) kg) participated in a randomised cross-over study. Subjects were provided one of four randomised meals on separate occasions (high carbohydrate, high protein, ad libitum or fasted baseline) prior to body composition and metabolic assessments. Regardless of macronutrient content, acute feeding increased DXA percent body fat (%fat) for the total sample and females (average constant error (CE):-0·30 %; total error (TE): 2·34 %), although not significant (P = 0·062); the error in males was minimal (CE: 0·11 %; TE: 0·86 %). DXA fat mass (CE: 0·26 kg; TE: 0·75 kg) and lean mass (LM) (CE: 0·83 kg; TE: 1·23 kg) were not altered beyond measurement error for the total sample. 4C %fat was significantly impacted from all acute feedings (avg CE: 0·46 %; TE: 3·7 %). 4C fat mass (CE: 0·71 kg; TE: 3·38 kg) and fat-free mass (CE: 0·55 kg; TE: 3·05 kg) exceeded measurement error for the total sample. RMR was increased for each feeding condition (TE: 1666·9 kJ/d; 398 kcal/d). Standard pre-testing fasting guidelines may be important when evaluating DXA and 4C %fat, whereas additional DXA variables (fat mass and LM) may not be significantly impacted by an acute meal. Measuring body composition via DXA under less stringent pre-testing guidelines may be valid and increase feasibility of testing in clinical settings.

Anthropometric characteristics of children living in food-insecure households in the USA.

OBJECTIVE: This study provides information on food insecurity and child malnutrition in a technologically advanced nation. DESIGN: Population-based study using multistage probability cluster sampling design to collect survey data. Multivariable regression models were used to determine associations between food security status and various malnutrition indices. SETTING: We used a national sample from the US National Health and Nutrition Examination Survey 2011-2014. PARTICIPANTS: The anthropometric and demographic data sets of 4121 children <7 years old were analysed for this study. RESULTS: Food-insecure infants younger than 6 months had shorter upper arm length (-0·4 cm, P = 0·012) and smaller mid-upper arm circumference (-0·5 cm, P = 0·004); likewise those aged 6 months-1 year had shorter upper arm length (-0·4 cm, P = 0·008), body length (-1·7 cm, P = 0·007) and lower body weight (-0·5 kg, P = 0·008). Food-insecure children younger than 2 years were more likely to be underweight (OR: 4·34; 95 % CI 1·99, 9·46) compared with their food-secure counterparts. Contrariwise, food-insecure children older than 5 years were more likely to be obese (OR: 3·12; 95 % CI 1·23, 7·96). CONCLUSIONS: Food insecurity associates with child growth deficits in the USA. Food-insecure infants and young children are generally smaller and shorter, whereas older children are heavier than their food-secure counterparts, implying a double burden of undernutrition-overnutrition associated with child food insecurity. Child food and nutrition programmes to improve food insecurity should focus on infants and children in the transition ages.

Metabolic effects of high-intensity interval training and essential amino acids.

High-intensity interval training (HIIT) promotes positive cardiometabolic and body composition changes. Essential amino acids (EAA) may support changes associated with HIIT, but evaluation of potential synergistic effects is lacking. The purpose of this study was to compare independent and combined effects of HIIT and EAA on total body composition and metabolism in men and women considered overweight/obese; an exploratory aim was to evaluate the modulatory effects of sex. Sixty-six healthy adults (50% female; Age: 36.7 ± 6.0 years; BMI: 32.0 ± 4.2 kg/m2) completed 8 weeks of: (1) HIIT, 2 days/weeks; (2) EAA supplementation, 3.6 g twice daily; (3) HIIT + EAA; or (4) control. Body composition, resting metabolic rate (RMR), substrate metabolism (respiratory exchange ratio; RER), and cardiorespiratory fitness were measured at baseline, 4 weeks, and 8 weeks; cardiometabolic blood markers were measured at baseline and 8 weeks. Differences between groups were assessed by linear mixed models covaried for baseline values, followed by 95% confidence intervals (CI) on adjusted mean change scores. There were no significant changes in body composition (p > 0.05) for any group. Changes in RER, but not RMR, occurred with HIIT (mean change; [95% CI]: - 0.04; [- 0.07, - 0.02]) and EAA (- 0.03; [- 0.06, - 0.01]) after 8 weeks. Cardiorespiratory fitness increased following 8 weeks of HIIT (+ 5.1 ml/kg/min [3.3,6.8]) and HIIT + EAA (+ 4.1 ml/kg/min [1.0,6.4]). Changes with HIIT + EAA were not significantly different from HIIT. There were no changes in cardiometabolic markers (p > 0.05) and no sex interaction (p > 0.05). HIIT is efficacious for promoting positive changes in cardiorespiratory fitness and resting substrate metabolism in adults considered overweight/obese. Addition of EAA did not significantly enhance HIIT-induced adaptations. ClinicalTrials.gov ID#NCT04080102.

Impact of occupational heat stress on worker productivity and economic cost.

Heat stress is a growing concern in the occupational setting as it endangers worker health, safety, and productivity. Heat-related reductions in physical work capacity and missed workdays directly and indirectly cause productivity losses and may substantially affect the economic wellbeing of the organization. This review highlights the physiological, physical, psychological, and financial harms of heat stress on worker productivity and proposes strategies to quantify heat-related productivity losses. Heat stress produces a vicious-cycle feedback loop that result in adverse outcomes on worker health, safety, and productivity. We propose a theoretical model for implementing an occupational heat safety plan that disrupts this loop, preventing heat-related productivity losses while improving worker health and safety.

Appendicular Body Composition Analysis: Validity of Bioelectrical Impedance Analysis Compared With Dual-Energy X-Ray Absorptiometry in Division I College Athletes.

Brewer, GJ, Blue, MNM, Hirsch, KR, Peterjohn, AM, and Smith-Ryan, AE. Appendicular body composition analysis: Validity of bioelectrical impedance analysis compared with dual-energy x-ray absorptiometry in Division I college athletes. J Strength Cond Res 33(11): 2920-2925, 2019-The purpose of this study was to evaluate validity of appendicular body composition measurements measured from a multifrequency bioelectrical impedance analysis (MF-BIA) compared with a dual-energy x-ray absorptiometry (DXA) criterion in Division I athletes. One hundred sixty male (n = 44) and female (n = 116) collegiate athletes were enrolled: Men's Cross Country (n = 15), football linemen (n = 29), Women's Soccer (n = 27), Women's Field Hockey (n = 27), Women's Cross Country (n = 13), Women's Gymnastics (n = 16), and Women's Lacrosse (n = 33). Appendicular fat mass (FM) of the arms (AFM, right AFM, left AFM) and legs (LFM, right LFM, left LFM), appendicular fat-free mass (FFM) of the arms (AFFM, RAFFM, LAFFM) and legs (LFFM, RLFFM, LLFFM), total body FM and FFM, and total body %fat were collected from both devices. MF-BIA significantly underestimated appendicular FFM of the arms (AFFM mean difference [MD]: -0.7 kg; RAFFM: -0.4 kg; LAFFM: -0.4 kg, p < 0.001) and legs (LFFM MD: -3.8 kg; RLFFM: -1.9 kg; LLFFM: -1.9 kg, p < 0.001), and FM of the legs (LFM MD: -2.5 kg; RLFM: -1.3 kg; LLFM: -1.3 kg, p < 0.001). There was no significant difference in appendicular FM measures of the arms (p = 0.174). All measures held true for male subjects and female subjects. Female subjects produced smaller differences compared with male subjects. The lack of validity, from raw and relative error, between the devices for most appendicular measures (FFM of arms and FFM and FM legs) and all total body measures (FM, FFM, and %fat) suggest that this MF-BIA may not be accurate in measuring a lean, athletic, population compared with DXA.

Immunohistochemistry Microarrays.

Immunohistochemistry (IHC) on tissue sections is widely used for quantifying the expression patterns of proteins and is part of the standard of care for cancer diagnosis and prognosis, but is limited to staining a single protein per tissue. Tissue microarray and microfluidics staining methods have emerged as powerful high throughput techniques, but they either only permit the analysis of a single protein per slide or require complex instrumentation and expertise while only staining isolated areas. Here, we introduce IHC microarrays (IHCµA) for multiplexed staining of intact tissues with preserved histological and spatial information. Droplets of a dextran solution containing antibodies were prespotted on a slide and snapped onto a preprocessed formalin-fixed, paraffin-embedded (FFPE) tissue section soaked in a polyethylene glycol solution. The antibodies are confined within the dextran droplets and locally stain the tissue below with a contrast similar to the one obtained by conventional IHC. The microarray of antibody droplets can be prespotted on a slide and stored, thus neither the preparation of the antibody solutions nor a sophisticated microarray spotter is needed. Sampling considerations with IHCµA were evaluated by taking three tissues with varying levels of cancer cells. A multiplex IHCµA with 180 spots targeting 8 cancer proteins was performed on a breast cancer tissue section to illustrate the potential of this method. This work opens the avenue of applying microarray technologies for conducting IHC on intact tissue slices and has great potential to be used in the discovery and validation of tissue biomarkers in human tumors.

Relationship Between Running Biomechanics and Core Temperature Across a Competitive Road Race.

BACKGROUND: Outdoor races introduce environmental stressors to runners, and core temperature changes may influence runners' movement patterns. This study assessed changes and determined relationships between sensor-derived running biomechanics and core temperature among runners across an 11.27-km road race. HYPOTHESIS: Core temperatures would increase significantly across the race, related to changes in spatiotemporal biomechanical measures. STUDY DESIGN: Cross-sectional cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Twenty runners (9 female, 11 male; age, 48 ± 12 years; height, 169.7 ± 9.1 cm; mass, 71.3 ± 13.4 kg) enrolled in the 2022 Falmouth Road Race were recruited. Participants used lightweight technologies (ingestible thermistors and wearable sensors) to monitor core temperature and running biomechanics throughout the race. Timestamps were used to align sensor-derived measures for 7 race segments. Observations were labeled as core temperatures generally within normal limits (<38°C) or at elevated core temperatures (≥38°C). Multivariate repeated measures analyses of variance were used to assess changes in sensor-derived measures across the race, with Bonferroni post hoc comparisons for significant findings. Pearson's r correlations were used to assess the relationship between running biomechanics and core temperature measures. RESULTS: Eighteen participants developed hyperthermic core temperatures (39.0°C ± 0.5°C); core temperatures increased significantly across the race (P < 0.01). Kinetic measures obtained from the accelerometers, including shock, impact, and braking g, all significantly increased across the race (P < 0.01); other sensor-derived biomechanical measures did not change significantly. Core temperatures were weakly associated with biomechanics (|r range|, 0.02-0.16). CONCLUSION: Core temperatures and kinetics increased significantly across a race, yet these outcomes were not strongly correlated. The observed kinetic changes may have been attributed to fatigue-related influences over the race. CLINICAL RELEVANCE: Clinicians may not expect changes in biomechanical movement patterns to signal thermal responses during outdoor running in a singular event.

Analysis of Exertion-Related Injuries and Fatalities in Laborers in the United States.

Laborers are particularly vulnerable to exertional injuries and illnesses, as they often engage in heavy physical work for prolonged hours, yet no studies have examined the top causes of catastrophic exertional injuries and fatalities among this population. The purpose of the investigation was to characterize the top causes of exertional injury and fatality within open access, Occupational Safety and Health Administration (OSHA) reportable data. A secondary analysis of OSHA reported injury and fatality data was performed through open access records from OSHA Severe Injury Reports (2015-2022) and OSHA fatality inspection data (2017-2020), respectively. The research team characterized each reported injury and fatality as "exertion-related" or "non-exertion-related. Injury and fatality rates were reported per 100,000 equivalent full-time worker years and included 95% confidence intervals (95% CI). Of 58,648 cases in the OSHA Severe Injury Report database from 2015-2020, 1682 cases (2.9%) were characterized as exertional (0.20 injuries per 100,000 full-time worker years, 95% CI: 0.19, 0.22). Heat-related injuries encompassed 91.9% of the exertional injuries (n = 1546). From the 2017-2022 OSHA fatality inspection database, 89 (1.9%) of 4598 fatalities were characterized as exertion-related (fatality rate: 0.0160 per 100,000 full-time equivalent workers, 95% CI: 0.009, 0.0134). The exertion-related fatalities primarily consisted of heat-related cases (87.6%). Exertion-related injuries and fatalities were most reported in Southeast states, in the construction and excavation industry, and among nonunionized workers. As heat stress continues to be recognized as an occupational health and safety hazard, this analysis further highlights the need for targeted interventions or further evaluation of the impact of heat stress on construction and excavation workers, nonunionized workers, and workers in Southeastern states.

The effect of heat mitigation strategies on thermoregulation and productivity during simulated occupational work in the heat in physically active young men.

Purpose: To investigate heat stress mitigation strategies on productivity and thermoregulatory responses during simulated occupational work in the heat. Methods: Thirteen physically active men (age, 25 ± 4 years; body mass,77.8 ± 14.7 kg; VO2peak, 44.5 ± 9.2 ml·kg-1·min-1) completed five randomized-controlled trials in a hot environment (40°C, 40% relative humidity). Each trial was 4.5 h in duration to simulate an outdoor occupational shift. Thermoregulatory responses (heart rate, HR; rectal temperature, Trec; mean skin temperature, Tsk), perceptual responses (rating of perceived exertion, RPE; thermal sensation; thermal comfort; fatigue) and productivity outcomes (box lifting repetitions, time to exhaustion) were examined in the following heat mitigation strategy interventions: (1) simulated solar radiation with limited fluid intake [SUN]; (2) simulated solar radiation with no fluid restrictions [SUN + H2O]; (3) shade (no simulated solar radiation during trial) with no fluid restrictions [SHADE + H2O]; (4) shade and cooling towels during rest breaks with no fluid restrictions [COOL + H2O]; and (5) shade with cooling towels, cooling vest during activity with no fluid restrictions [COOL + VEST + H2O]. Results: [COOL + VEST + H2O] had lower Trec compared to [SUN] [p = 0.004, effect size(ES) = 1.48], [SUN + H2O] (p < 0.001, ES = -1.87), and [SHADE + H2O] (p = 0.001, ES = 1.62). Average Tsk was lower during the treadmill and box lifting activities in the [COOL + VEST + H2O] compared to [SUN] (p < 0.001, ES = 7.92), [SUN + H2O] (p < 0.001,7.96), [SHADE + H2O] (p < 0.001), and [COOL + H2O] (p < 0.001, ES = 3.01). There were performance differences during the [COOL + VEST + H2O] (p = 0.033) and [COOL + H2O] (p = 0.023) conditions compared to [SUN] during phases of the experimental trial, however, there were no differences in total box lifting repetitions between trials (p > 0.05). Conclusion: Our results suggest that during a simulated occupational shift in a laboratory setting, additional heat mitigation strategies ([COOL + VEST + H2O] and [COOL + H2O]) reduced physiological strain and improved box lifting performance to a greater degree than [SUN]. These differences may have been attributed to a larger core to skin temperature gradient or reduction in fatigue, thermal sensation, and RPE during [COOL + H2O] and [COOL + VEST + H2O]. These data suggest that body cooling, hydration, and "shade" (removal of simulated radiant heat) as heat stress mitigation strategies should be considered as it reduces physiological strain while producing no additional harm.

The case for cancer-associated fibroblasts: essential elements in cancer drug discovery?

Although cancer-associated fibroblasts (CAFs) have gained increased attention for supporting cancer progression, current CAF-targeted therapeutic options are limited and failing in clinical trials. As the largest component of the tumor microenvironment (TME), CAFs alter the biochemical and physical structure of the TME, modulating cancer progression. Here, we review the role of CAFs in altering drug response, modifying the TME mechanics and the current models for studying CAFs. To provide new perspectives, we highlight key considerations of CAF activity and discuss emerging technologies that can better address CAFs; and therefore, increase the likelihood of therapeutic efficacy. We argue that CAFs are crucial components of the cancer drug discovery pipeline and incorporating these cells will improve drug discovery success rates.

Recent advances in cancer research have improved our understanding of disease progression; however, the number of drugs failing in clinical trials remains high and therefore, present a critical challenge for cancer drug discovery. Although the interactions of the tissue surrounding the tumor, the tumor microenvironment, are now considered key targets for new interventions in cancer, the role of microenvironment is largely absent in drug discovery pipelines. Here we explore the role of the most prominent cell type in the tumor microenvironment, cancer-associated fibroblasts (CAFs), in altering cancer therapy response and ultimately patient outcome. To provide new perspectives for future studies, we draw attention to key complications of CAF biology and highlight emerging technologies that could be used to address this. We believe including CAFs in drug discovery, whether for targeting cancer cells or the microenvironment, will allow for a better understanding of therapeutic efficacy and ultimately improve clinical outcome.

Sex differences and considerations for female specific nutritional strategies: a narrative review.

Although there is a plethora of information available regarding the impact of nutrition on exercise performance, many recommendations are based on male needs due to the dominance of male participation in the nutrition and exercise science literature. Female participation in sport and exercise is prevalent, making it vital for guidelines to address the sex-specific nutritional needs. Female hormonal levels, such as estrogen and progesterone, fluctuate throughout the mensural cycle and lifecycle requiring more attention for effective nutritional considerations. Sex-specific nutritional recommendations and guidelines for the active female and female athlete have been lacking to date and warrant further consideration. This review provides a practical overview of key physiological and nutritional considerations for the active female. Available literature regarding sex-specific nutrition and dietary supplement guidelines for women has been synthesized, offering evidenced-based practical information that can be incorporated into the daily lives of women to improve performance, body composition, and overall health.

Effects of Face Mask Use on Objective and Subjective Measures of Thermoregulation During Exercise in the Heat.

BACKGROUND: While increased face mask use has helped reduce COVID-19 transmission, there have been concerns about its influence on thermoregulation during exercise in the heat, but consistent, evidence-based recommendations are lacking. HYPOTHESIS: No physiological differences would exist during low-to-moderate exercise intensity in the heat between trials with and without face masks, but perceptual sensations could vary. STUDY DESIGN: Crossover study. LEVEL OF EVIDENCE: Level 2. METHODS: Twelve physically active participants (8 male, 4 female; age = 24 ± 3 years) completed 4 face mask trials and 1 control trial (no mask) in the heat (32.3°C ± 0.04°C; 54.4% ± 0.7% relative humidity [RH]). The protocol was 60 minutes of walking and jogging between 35% and 60% of relative VO2max. Rectal temperature (Trec), heart rate (HR), temperature and humidity inside and outside of the face mask (Tmicro_in, Tmicro_out, RHmicro_in, RHmicro_out) and perceptual variables (rating of perceived exertion (RPE), thermal sensation, thirst sensation, fatigue level, and overall breathing discomfort) were monitored throughout all trials. RESULTS: Mean Trec and HR increased at 30- and 60-minute time points compared with 0-minute time points, but no difference existed between face mask trials and control trials (P > 0.05). Mean Tmicro_in, RHmicro_in, and humidity difference inside and outside of the face mask (ΔRHmicro) were significantly different between face mask trials (P < 0.05). There was no significant difference in perceptual variables between face mask trials and control trials (P > 0.05), except overall breathing discomfort (P < 0.01). Higher RHmicro_in, RPE, and thermal sensation significantly predicted higher overall breathing discomfort (r2 = 0.418; P < 0.01). CONCLUSION: Face mask use during 60 minutes of low-to-moderate exercise intensity in the heat did not significantly affect Trec or HR. Although face mask use may affect overall breathing discomfort due to the changes in the face mask microenvironment, face mask use itself did not cause an increase in whole body thermal stress. CLINICAL RELEVANCE: Face mask use is feasible and safe during exercise in the heat, at low-to-moderate exercise intensities, for physically active, healthy individuals.

Impact of Follicular Menstrual Phase on Body Composition Measures and Resting Metabolism.

PURPOSE: This study aimed to identify the effects of early follicular (EF) and midfollicular (MF) menstrual phases on body composition, resting metabolic rate (RMR), and respiratory quotient (RQ) assessment accuracy to identify an optimal testing period. METHODS: Body composition was obtained from a four-compartment (4C) criterion model (fat mass (FM), fat-free mass, body fat percent, and dual-energy x-ray absorptiometry (DXA; FM, lean mass (LM), trunk FM, and trunk LM) in 19 eumenorrheic females (mean ± SD: age, 21.3 ± 3.1 yr, body mass index, 23.6 ± 1.8 kg·m-2). RMR (kcal·d-1) and RQ (a.u.) were measured via indirect calorimetry for 25 min. Body composition, RMR, and RQ were measured during the EF and MF phases. Dependent-samples t-tests were used to compare outcomes between EF and MF. RESULTS: 4C outcomes were similar between phases (P > 0.05). During EF, the following 4C components were significantly greater (P < 0.05): body volume (mean difference (MD) ± SD, 0.70 ± 1.05 L), extracellular fluid (MD ± SD, 0.27 ± 0.51 L), and body mass (MD ± SD, 0.56 ± 0.80 kg). DXA-measured LM, body fat percent, trunk LM, and trunk FM were similar (P > 0.05); however, DXA FM was significantly greater during EF (MD ± SD, 0.29 ± 0.40 kg; P = 0.005), yet within measurement error of the device. Although RMR was not significantly different between phases (MD ± SD, 6.0 ± 190.93 kcal·d-1; P > 0.05), RQ was significantly higher during EF (mean ± SD, 0.03 ± 0.06 a.u.; P = 0.029) compared with MF. CONCLUSIONS: Body composition from 4C and DXA do not seem to be affected beyond measurement error as a result of compartmental changes from the menstrual cycle. During MF, women oxidized more fat as demonstrated by a lower RQ. Researchers should aim to be more inclusive and schedule testing for females within 11-12 d from the onset of menstruation.

Validation of InBody 770 bioelectrical impedance analysis compared to a four-compartment model criterion in young adults.

BACKGROUND: Multi-frequency bioelectrical impedance analysis (MF-BIA) offers enhanced body composition outcomes in a time-efficient manner. The accuracy of stand-up MF-BIA compared against a four-compartment (4C) criterion lacks evidence. OBJECTIVES: To validate a stand-up MF-BIA compared to a 4C criterion for fat mass (FM), fat-free mass (FFM) and body fat percentage (%fat). SUBJECTS/METHODS: Eighty-two healthy (32% men) normal-weight (BMI: 18.5-24.9 kg/m2 ) young adults were measured for body composition determined from a stand-up MF-BIA and 4C model. Validity statistics included total error (TE) and standard error of the estimate (SEE) to examine prediction error between methods. RESULTS: For the total sample, prediction error was the highest for %fat (TE = 4.2%; SEE = 3.9%) followed by FM (TE = 2.4 kg; SEE = 2.2 kg) and FFM (TE = 2.4 kg; SEE = 2.2 kg). In men, %fat (TE = 2.5%; SEE = 2.2%) and FM (TE = 1.9 kg; SEE = 1.6 kg) were ideal; FFM was similar to FM (TE = 1.9 kg; SEE = 1.6 kg). In women, %fat (TE = 4.7%; SEE = 4.4%) ranged from good to fairly good, and FM was very good to excellent (TE = 2.6 kg; SEE = 2.4 kg); FFM was similar to FM (TE = 2.6 kg; SEE = 2.3 kg). CONCLUSIONS: Stand-up MF-BIA may overestimate %fat and FM, and underestimate FFM compared to a 4C model. FM and FFM estimates from MF-BIA demonstrate good agreement to a 4C model and may be a practical measure of body composition in normal-weight adults. The highest error was seen in %fat for both sexes, with greater error in women.

Validity of a 3-dimensional body scanner: comparison against a 4-compartment model and dual energy X-ray absorptiometry.

Three-dimensional (3D) body scanner technology for body composition assessment is expanding. The aim of this study was to assess the validity of a 3D body scanner. One hundred and ninety-four participants (43% male; age: 23.52 ± 5.47 years; body mass index: 23.98 ± 3.24 kg·m-2) were measured using 3D scanner and a 4-compartment (4C) model utilizing dual-energy X-ray absorptiometry (DXA), air displacement plethysmography, and bioelectrical impedance spectroscopy. Dependent t tests, validity statistics including total error (TE), standard error of the estimate, constant error, and Bland-Altman analyses were utilized. Compared with 4C, 3D scanner fat mass (FM) [mean difference (MD; 3D-4C): 2.66 kg ± 3.32 kg] and percent body fat (%BF) (MD: 4.13% ± 5.36%) were significantly (p < 0.001) over-predicted; fat free mass (FFM) was significantly underpredicted (MD: -3.15 kg ± 4.75 kg; p < 0.001). 3D demonstrated poor validity indicated by TE (%BF: 5.61%; FM: 4.50 kg; FFM: 5.69 kg). In contrast, there were no significant differences between 3D and DXA measures; 3D scanner demonstrated acceptable measurement for %BF (TE: 4.25%), FM (TE: 2.92 kg), and lean mass (TE: 3.86 kg). Compared with the 4C criterion, high TE values indicated 3D estimates were not valid. In contrast, 3D estimates produced acceptable measurement agreement when compared with DXA; an average overestimation of %BF by 5.31% (vs. 4C) and 4.20% (vs. DXA) may be expected. Novelty: 3D body composition estimates are not valid compared with the 4-C criterion model. 3D estimates appeared to be more valid in females, compared with males. When compared with DXA, 3D estimates were acceptable.

High-intensity interval training and essential amino acid supplementation: Effects on muscle characteristics and whole-body protein turnover.

The purpose of this study was to compare the independent and combined effects of high-intensity interval training (HIIT) and essential amino acids (EAA) on lean mass, muscle characteristics of the quadriceps, and 24-hr whole-body protein turnover (WBPT) in overweight and obese adults. An exploratory aim was to evaluate potential modulatory effects of sex. Sixty-six adults (50% female; Age: 36.7 ± 6.0 yrs; %BF: 36.0 ± 7.8%) were assigned to 8 wks of: (a) HIIT, 2 days/wk; (b) EAA supplementation, 3.6 g twice daily; (c) HIIT + EAA; or (d) control. At baseline, 4 wks, and 8 wks, total body, thigh LM and muscle characteristics were measured via dual-energy x-ray absorptiometry and B-mode ultrasound, respectively. In a subsample, changes in WBPT was measured using [N15 ]alanine. Differences between groups were assessed using linear mixed models adjusted for baseline values, followed by 95% confidence intervals on adjusted mean change scores (Δ). HIIT and HIIT + EAA improved thigh LM (Δ: +0.17 ± 0.05 kg [0.08, 0.27]; +0.22 ± 0.05 kg [0.12,0.31]) and vastus lateralis cross-sectional area (Δ: +2.73 ± 0.52 cm2 [1.69,3.77]; +2.64 ± 0.53 cm2 [1.58,3.70]), volume (Δ: +54.50 ± 11.69 cm3 [31.07, 77.92]; +62.39 ± 12.05 cm3 [38.26, 86.52]), and quality (Δ: -5.46 ± 2.68a.u. [-10.84, -0.09]; -7.97 ± 2.76a.u.[-13.49, -2.45]). Protein synthesis, breakdown, and flux were greater with HIIT + EAA and EAA compared to HIIT (p < .05). Sex differences were minimal. Compared to women, men tended to respond more to HIIT, with or without EAA. For women, responses were greater with HIIT + EAA than HIIT. In overweight and obese adults, 8 weeks of HIIT, with or without EAA, improved thigh LM size and quality; EAA may enhance muscular adaptation via increases in protein turnover, supporting greater improvements in muscular size and quality.