Air speed and direction affect metabolic and thermoregulatory responses during walking and running in a temperate environment.

Revisiting classical experiments on the impact of air resistance on metabolic rate, we aimed to overcome limitations of previous research, notably: low participant numbers ( = 1-3), highly turbulent wind, and confounding effects of rising body temperature. In a custom-built wind tunnel with reduced turbulence, 14 participants (8 males, 6 females) walked (5 km·h) and ran on a treadmill (70%V̇o) at 0, 2, 4, and 6 m·s headwind or tailwind in a counterbalanced design, with rest breaks between each exposure to avoid rises in body core temperature. Oxygen consumption (V̇o) exhibited strong linear relationships versus wind direction, dynamic pressure, and air speed squared (V), lower in magnitude for headwind than tailwind.

Comparing the efficacy of different climate indices for prediction of labor loss, body temperatures, and thermal perception in a wide variety of warm and hot climates.

The purpose of this study was to investigate which climate/heat indices perform best in predicting heat-induced loss of physical work capacity (PWC). Integrating data from earlier studies, data from 982 exposures (75 conditions) exercising at a fixed cardiovascular load of 130 beats·min, in varying temperatures (15-50°C), humidities (20-80%), solar radiation (0-800 W·m), wind (0.2-3.

A thermoregulation model based on the physical and physiological characteristics of Chinese elderly.

Given the increasing aging population and rising living standards in China, developing an accurate and straightforward thermoregulation model for the elderly has become increasingly essential. To address this need, an existing one-segment four-node thermoregulation model for the young was selected as the base model. This study developed the base model considering age-related physical and physiological changes to predict mean skin temperatures of the elderly.

Quantifying the impact of heat on human physical work capacity; part IV: interactions between work duration and heat stress severity.

High workplace temperatures negatively impact physical work capacity (PWC). Although PWC loss models with heat based on 1-h exposures are available, it is unclear if further adjustments are required to accommodate repeated work/rest cycles over the course of a full work shift. Therefore, we examined the impact of heat stress exposure on human PWC during a simulated work shift consisting of six 1-h work-rest cycles.

Age comparison of changes in local warm and cold sensitivity due to whole body cooling.

Purpose: This study investigated the influence of whole body cooling on local thermal sensitivity to warm (40°C) and cold (20°C) stimuli in 10 young (age: 24 ± 2 yrs) and 10 older males (age: 69 ± 4 yrs).

Methods: Local warm and cold sensitivity was assessed at eight body regions using a 25 cm pressure controlled thermal probe after 40 min of whole body exposure to a thermoneutral (NEUT: 25°C/40% RH) and a cold (COLD: 12°C/50% RH) environment. Gastrointestinal temperature (T), mean and local skin temperature, heart rate, whole body thermal sensation and comfort, and skin blood flow were also measured.

Self-Selected Motivational Music Enhances Physical Performance in Normoxia and Hypoxia in Young Healthy Males.

Humans exposed to hypoxia are susceptible to physiological and psychological impairment. Music has ergogenic effects through enhancing psychological factors such as mood, emotion, and cognition. This study aimed to investigate music as a tool for mitigating the performance decrements observed in hypoxia.

Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices.

Increasing air movement can alleviate or exacerbate occupational heat strain, but the impact is not well defined across a wide range of hot environments, with different clothing levels. Therefore, we combined a large empirical study with a physical model of human heat transfer to determine the climates where increased air movement (with electric fans) provides effective body cooling. The model allowed us to generate practical advice using a high-resolution matrix of temperature and humidity.

Quantifying the impact of heat on human physical work capacity; part III: the impact of solar radiation varies with air temperature, humidity, and clothing coverage.

Heat stress decreases human physical work capacity (PWC), but the extent to which solar radiation (SOLAR) compounds this response is not well understood. This study empirically quantified how SOLAR impacts PWC in the heat, considering wide, but controlled, variations in air temperature, humidity, and clothing coverage. We also provide correction equations so PWC can be quantified outdoors using heat stress indices that do not ordinarily account for SOLAR (including the Heat Stress Index, Humidex, and Wet-Bulb Temperature).

The use of infrared thermography for the dynamic measurement of skin temperature of moving athletes during competition; methodological issues.

. To investigate the use of infrared thermography (IRT) for skin temperature measurement of moving athletes during competition and its sensitivity to factors that are traditionally standardised..

Aerobic fitness as a parameter of importance for labour loss in the heat.

Objectives: To derive an empirical model for the impact of aerobic fitness (maximal oxygen consumption; V̇O in mL∙kg∙min) on physical work capacity (PWC) in the heat.

Design: Prospective, repeated measures.

Methods: Total work completed during 1 h of treadmill walking at a fixed heart rate of 130 b∙min was assessed in 19 young adult males across a variety of warm and hot climate types, characterised by wet-bulb globe temperatures (WBGT) ranging from 12 to 40 °C.

Mental fatigue independent of boredom and sleepiness does not impact self-paced physical or cognitive performance in normoxia or hypoxia.

This study investigated the individual and combined effects of mental fatigue (MF) and hypoxia (HYP) on physical and cognitive performance. Fifteen males (24 ± 3 years) completed one familiarization session and six experimental trials, including: 1) normoxia (0.209 FiO) and no MF; 2) normoxia (0.

An advanced empirical model for quantifying the impact of heat and climate change on human physical work capacity.

Occupational heat stress directly hampers physical work capacity (PWC), with large economic consequences for industries and regions vulnerable to global warming. Accurately quantifying PWC is essential for forecasting impacts of different climate change scenarios, but the current state of knowledge is limited, leading to potential underestimations in mild heat, and overestimations in extreme heat. We therefore developed advanced empirical equations for PWC based on 338 work sessions in climatic chambers (low air movement, no solar radiation) spanning mild to extreme heat stress.

Independent and combined impact of hypoxia and acute inorganic nitrate ingestion on thermoregulatory responses to the cold.

Purpose: This study assessed the impact of normobaric hypoxia and acute nitrate ingestion on shivering thermogenesis, cutaneous vascular control, and thermometrics in response to cold stress.

Method: Eleven male volunteers underwent passive cooling at 10 °C air temperature across four conditions: (1) normoxia with placebo ingestion, (2) hypoxia (0.130 FO) with placebo ingestion, (3) normoxia with 13 mmol nitrate ingestion, and (4) hypoxia with nitrate ingestion.

Individual Responses to Heat Stress: Implications for Hyperthermia and Physical Work Capacity.

Background: Extreme heat events are increasing in frequency, severity, and duration. It is well known that heat stress can have a negative impact on occupational health and productivity, particularly during physical work. However, there are no up-to-date reviews on how vulnerability to heat changes as a function of individual characteristics in relation to the risk of hyperthermia and work capacity loss.

Body mapping of regional sweat distribution in young and older males.

Purpose: Given the pressing impact of global warming and its detrimental effect on the health of older populations, understanding age-related changes in thermoregulatory function is essential. Age differences in regional sweat distribution have been observed previously, but given the typically small measurement areas assessed, the development of whole body sweat maps for older individuals is required. Therefore, this study investigated age-related differences in regional sweat distribution in a hot environment (32 °C/50%RH) in young and older adults, using a body mapping approach.

Occupational Heat Stress and Practical Cooling Solutions for Healthcare and Industry Workers During the COVID-19 Pandemic.

Treatment and management of severe acute respiratory syndrome coronavirus-2, which causes coronavirus disease (COVID-19), requires increased adoption of personal protective equipment (PPE) to be worn by workers in healthcare and industry. In warm occupational settings, the added burden of PPE threatens worker health and productivity, a major lesson learned during the West-African Ebola outbreak which ultimately constrained disease control. In this paper, we comment on the link between COVID-19 PPE and occupational heat strain, cooling solutions available to mitigate occupational heat stress, and practical considerations surrounding their effectiveness and feasibility.

Reliability and validity of methods in the assessment of cold-induced shivering thermogenesis.

Purpose: To compare two analytical methods for the estimation of the shivering onset inflection point, segmental regression and visual inspection of data, and to assess the test-retest reliability and validity of four metrics of shivering measurement; oxygen uptake (V̇O), electromyography (EMG), mechanomyography (MMG) and bedside shivering assessment scale (BSAS).

Methods: Ten volunteers attended three identical experimental sessions involving passive deep-body cooling via cold water immersion at 10 °C. V̇O, EMG, and MMG were continuously assessed, while the time elapsed at each BSAS stage was recorded.

A comparison of methods used for inducing mental fatigue in performance research: individualised, dual-task and short duration cognitive tests are most effective.

Despite research indicating the negative impact that mental fatigue has on physical and cognitive performance, whether this is a result of mental fatigue or a state of under-arousal remains unclear. The current research aimed to explore the effectiveness of the methods being used to induce mental fatigue. Twelve participants attended six sessions in which two cognitive tests, the AX-continuous performance test (AX-CPT) and the TloadDback test, were compared for their effectiveness in inducing mental fatigue.

Sweat distribution and perceived wetness across the human foot: the effect of shoes and exercise intensity.

This study investigates foot sweat distribution with and without shoes and the relationship between foot sweat distribution and perceived wetness to enhance guidance for footwear design. Fourteen females performed low-intensity running with nude feet and low- and high-intensity running with shoes (55%VO and 75%VO, respectively) on separate occasions. Right foot sweat rates were measured at 14 regions using absorbent material applied during the last 5 min of each work intensity.

The use of infrared thermal imaging to measure spatial and temporal sweat retention in clothing.

In our previous laboratory study a 'destructive' gravimetric method was developed to quantify local garment sweat absorption. While this currently is the only methodology that permits direct and analytical measurements of garment regional sweat absorption, the latter approach is time-consuming and expensive, therefore, of limited applicability. As such, in this study, we wanted to assess whether infrared thermography could be used as an indirect method to estimate garment regional sweat absorption, right after exercise, in a 'non-destructive' fashion.

The Threshold Ambient Temperature for the Use of Precooling to Improve Cycling Time-Trial Performance.

Purpose: Cycling time-trial performance can be compromised by moderate to high ambient temperatures. It has become commonplace to implement precooling prior to competition to alleviate this performance decline. However, little is known about the ambient temperature threshold above which precooling becomes an effective strategy for enhancing endurance performance.

Clothing comfort during physical exercise - Determining the critical factors.

Clothing comfort is determined by multiple material and design factors. Wetness at the skin-clothing interface mainly impacts wear comfort. The current study investigated the combined effect of fabric contact area, fabric absolute sweat content and fabric moisture saturation percentage on wetness and stickiness sensations, during exercise.

Anchoring biases affect repeated scores of thermal, moisture, tactile and comfort sensations in transient conditions.

In this study, we addressed potential biases which can occur when sensorial scores of temperature, wetness and discomfort are repeatedly reported, in transient exercise conditions. We pointed out that, when repeatedly reported, previous sensorial scores can be set by the participants as reference values and the subsequent score may be given based on the previous point of reference, the latter phenomenon leading to a bias which we defined as 'anchoring bias'. Indeed, the findings shown that subsequent sensorial scores are prone to anchoring biases and that the bias consisted in a systematically higher magnitude of sensation as compared to when reported a single time only.

Spatial and temporal migration of sweat: from skin to clothing.

Purpose: Moisture accumulation in clothing affects human performance and productivity through its impact on thermal balance and various aspects of discomfort. Building on our laboratory's work on mapping sweat production across the body, this study aimed to obtain detailed spatial and temporal maps showing how this sweat migrates into a single clothing layer (T-shirt) during physical exercise.

Method: Eight male participants performed running exercise in a warm environment.

Safer anaesthetic rooms: Human factors/ergonomics analysis of work practices.

The aim of this study was to analyse the design of anaesthetic rooms using human factors and ergonomics (HFE) methods. The methods used were hierarchical task analysis, link analysis and anthropometry. The study found several latent design errors which negatively affected drug and patient preparation tasks.