Body temperature manipulation and exercise performance in athletically trained males

Exercise or activity in high ambient temperatures offers a particular challenge to the thermoregulatory system. It is likely that mechanisms such as sweat evaporation alone are not sufficient for maintaining body temperature within a safe limit (~36.5-38.5˚C) and below 40˚C, which may result in impaired physiological function and performance. Exogenous cooling may be of benefit prior to, during and after events that place increased thermal strain due to increased metabolic heat production and elevated environmental temperatures upon the thermoregulatory system. Conversely, in situations where it is not possible to maintain body temperature via either continued physical activity or elevated ambient temperatures, exogenous heating may be required in order to allow optimal physiological performance. Few studies have directly aligned cooling devices with data detailing effective target regions for cooling to allow a pre-cooling garment to be of minimal weight but maximal cooling efficiency. Conversely, no study has considered the effect of muscle temperature maintenance during rest periods on subsequent power-based activities. The aim of this thesis was to determine ways in which body temperature manipulation is capable of improving exercise performance in both power and endurance-based events. It was hypothesised that the manipulation of body temperature will result in subsequent changes in body temperature that would improve performance. Specifically, the use of pre-cooling would result in a reduction of body temperature and improve endurance exercise performance. Conversely, maintaining Tm following warm up completion would have a beneficial effect on sprint and power related performance. Study one set out to determine differences in regional body heat loss in 12 individual anatomical zones using a water perfused suit. Data obtained from this initial study allowed for the specific targeting of regions that were identified as having high rates of heat loss in subsequent studies that focused on pre-cooling and performance. The anatomical regions identified as having high potential affinity for heat exchange with the surrounding environment and cooling devices were the hands, forearms, upper and lower back and torso. Subsequent studies demonstrated that cooling of these areas was capable of lowering thermal sensation and improving thermal comfort prior to and during exercise in moderate environmental conditions (24˚C, 50% RH). In these moderate conditions, there was no statistically significant improvement in treadmill based self-paced 5000m running performance. However, in hot conditions (35˚C 50% RH), the use of a cooling vest and sleeves did yield a significant improvement in cycling time trial performance, which equated to 4.8%. This leads to the suggestion that there may be a threshold ambient temperature, above which pre-cooling becomes an important tool in maximizing performance potential. A parallel area of investigation, on the other side of the temperature spectrum, was the effect of muscle temperature manipulation on power-based exercise performance. The relationship between increased muscle temperature and power output is well established, however little is known about the effect of enforced rest or recovery between two bouts of exercise. Therefore, two studies were conducted to establish what affect a delay between warm up completion and exercise has on muscle temperature and subsequent sprint cycling performance. It was shown that with 30-minutes of rest between exercise bouts wearing tracksuit trousers, muscle temperature declined significantly (~1-1.5˚C). This decline was attenuated with the use of external passive electrical heating during the recovery compared to recovery completed in tracksuit trousers alone. The attenuated decline in muscle temperature following the use of the heated trousers resulted in an improvement in sprint cycling performance (~9%), with the use of insulated trousers having no effect on any variables measured, all relative to wearing tracksuit trousers in the rest period. In a follow-up study, the effect of implementing the heated trousers during the warm up and in addition to the rest period had on muscle temperature increase and sprint performance. A secondary area of investigation in this study was to determine the linearity of muscle temperature decline following warm up cessation. This study demonstrated that there was no additional benefit of combining passive heating with an active warm up on either muscle temperature elevations or subsequent sprint performance compared to the active warm up alone. It was shown that when the no heating was used at any stage, muscle temperature declined exponentially. However, when the heated trousers were used during recovery and/or during warm up, muscle temperature levelled off at a higher value towards the end of the recovery period. This study was also able to show significant improvements in absolute, relative and mean power output following the use of the heated trousers in the warm up and recovery, or the recovery alone. This thesis has identified ways in which body temperature may be manipulated in order to benefit both sprint and endurance exercise performance, using both pre-cooling and active heating. A novel concept for minimizing muscle temperature decline during periods of inactivity between different rounds of competition was shown to maximize sprint performance yielding significant improvements in peak and mean power outputs

A multi-level examination of school programs, policies and resources associated with physical activity among elementary school youth in the PLAY-ON study

<p>Abstract</p> <p>Background</p> <p>Given the decline in physical activity (PA) levels among youth populations it is vital to understand the factors that are associated with PA in order to inform the development of new prevention programs. Many studies have examined individual characteristics associated with PA among youth yet few have studied the relationship between the school environment and PA despite knowing that there is variability in student PA levels across schools.</p> <p>Methods</p> <p>Using multi-level logistic regression analyses we explored the school- and student-level characteristics associated with PA using data from 2,379 grade 5 to 8 students attending 30 elementary schools in Ontario, Canada as part of the PLAY-Ontario study.</p> <p>Results</p> <p>Findings indicate that there was significant between-school random variation for being moderately and highly active; school-level differences accounted for 4.8% of the variability in the odds of being moderately active and 7.3% of the variability in the odds of being highly active. Students were more likely to be moderately active if they attended a school that used PA as a reward and not as discipline, and students were more likely to be highly active if they attended a school with established community partnerships. Important student characteristics included screen time sedentary behaviour, participating in team sports, and having active friends.</p> <p>Conclusion</p> <p>Future research should evaluate if the optimal population level impact for school-based PA promotion programming might be achieved most economically if intervention selectively targeted the schools that are putting students at the greatest risk for inactivity.</p

The effect of passive heating on heat shock protein 70 and interleukin-6: a possible treatment tool for metabolic diseases?

Increasing physical activity remains the most widely publicized way of improving health and wellbeing. However, in populations that benefit most from exercise (EX), adherence is often poor and alternatives to EX are important to bring about health improvements. Recent work suggests a role for passive heating (PH) and heat shock proteins (HSP) in improving cardio-metabolic health. The aim of this study was to investigate the expression of HSP70 and interleukin-6 in response to either EX or PH and the subsequent effect on glucose control. Fourteen males volunteered and were categorized lean (BMI 23.5 ± 2.2 kg·m−2) or overweight (29.2 ± 2.7 kg·m−2) and completed 60 minutes of either moderate cycling at a fixed rate of metabolic heat production (EX) or warm water immersion in 40°C water (PH). Extracellular HSP70 increased from baseline in both conditions with no differences between PH (0.98 ± 1.1 ng·mL−1) or EX (0.84 ± 1.0 ng·mL−1, p = 0.814). IL-6 increased following both conditions with a two-fold increase after PH and four-fold after EX. Energy expenditure increased by 61.0 ± 14.4 kcal·h−1 (79%) after PH. Peak glucose concentration after a meal immediately following PH was reduced when compared with EX (6.3 ± 1.4 mmol·L−1 versus 6.8 ± 1.2 mmol·L−1; p < 0.05). There was no difference in 24-hour glucose area under the curve (AUC) between conditions. These data indicate the potential for thermal therapy as an alternative treatment and management strategy for those at risk of developing metabolic disease where adherence, or ability to EX, may be compromised

External muscle heating during warm-up does not provide added performance benefit above external heating in the recovery period alone

Having previously shown the use of passive external heating between warm-up completion and sprint cycling to have had a positive effect on muscle temperature (T m) and maximal sprint performance, we sought to determine whether adding passive heating during active warm up was of further benefit

A comparison of APD and SPAD based receivers for visible light communications

Visible light communications (VLC) is an alternative method of indoor wireless communications that requires sensitive receivers. Ideally, single photon avalanche detectors (SPADs) could be used to create more sensitive receivers. However, the dead-time, finite output pulse width and photon detection efficiency of existing SPAD arrays limits their sensitivity and bandwidth. In this paper an accurate equation for the impact of dead-time on the sensitivity of a SPAD array is presented. In addition the impact of the width of the output pulses on the on-off keying (OOK) data rate is investigated. Finally, a comparison between receivers containing an APD and a large array of SPADs shows that although the receiver containing the SPAD is more sensitive in the dark the APD-based receiver is more sensitive in normal operating condition. However, the models that predict the performance of both receivers suggest that newer SPAD arrays will enable significant improvements in receiver sensitivity

Light Modulates the Biosynthesis and Organization of Cyanobacterial Carbon Fixation Machinery through Photosynthetic Electron Flow

Cyanobacteria have evolved effective adaptive mechanisms to improve photosynthesis and CO2 fixation. The central CO2-fixing machinery is the carboxysome, which is composed of an icosahedral proteinaceous shell encapsulating the key carbon fixation enzyme, Rubisco, in the interior. Controlled biosynthesis and ordered organization of carboxysomes are vital to the CO2-fixing activity of cyanobacterial cells. However, little is known about how carboxysome biosynthesis and spatial positioning are physiologically regulated to adjust to dynamic changes in the environment. Here, we used fluorescence tagging and live-cell confocal fluorescence imaging to explore the biosynthesis and subcellular localization of β-carboxysomes within a model cyanobacterium, Synechococcus elongatus PCC7942, in response to light variation. We demonstrated that β-carboxysome biosynthesis is accelerated in response to increasing light intensity, thereby enhancing the carbon fixation activity of the cell. Inhibition of photosynthetic electron flow impairs the accumulation of carboxysomes, indicating a close coordination between β-carboxysome biogenesis and photosynthetic electron transport. Likewise, the spatial organization of carboxysomes in the cell correlates with the redox state of photosynthetic electron transport chain. This study provides essential knowledge for us to modulate the β-carboxysome biosynthesis and function in cyanobacteria. In translational terms, the knowledge is instrumental for design and synthetic engineering of functional carboxysomes into higher plants to improve photosynthesis performance and CO2 fixation. Compartmentalization of metabolic pathways in cells provides the fundamental basis for enhancing and modulating the cellular metabolism. Many prokaryotes have evolved specialized metabolic organelles, known as bacterial microcompartments, to sequester key metabolic pathways and thereby improve the efficiency of metabolic activities (for reviews, see Kerfeld et al., 2010; Bobik et al., 2015). Unlike eukaryotic organelles, bacterial microcompartments are assembled entirely by proteins. These organelles consist of interior enzymes that catalyze sequential metabolic reactions (Yeates et al., 2010), surrounded by a single-layer proteinaceous shell (Kerfeld et al., 2005; Tsai et al., 2007; Tanaka et al., 2008; Sutter et al., 2016). The shell facets are composed of hexameric and pentameric proteins, resulting in an overall shell architecture resembling an icosahedral viral capsid (Kinney et al., 2011; Hantke et al., 2014; Kerfeld and Erbilgin, 2015). Interactions between shell proteins are important for the self-assembly of the shell (Sutter et al., 2016). The selectively permeable shell serves to concentrate enzymes and substrates, mediate flux of metabolites, modulate the redox state, and prevent toxic intermediates from diffusing into the cytoplasm (Havemann et al., 2002; Yeates et al., 2008). Carboxysomes were the first bacterial microcompartments to be discovered and are widely distributed among cyanobacteria and some chemoautotrophs as the central machinery for the fixation of CO2 (Shively et al., 1973). Two different types of carboxysomes have been identified (α- and β-carboxysomes), according to the types of the CO2-fixing enzyme, Rubisco (form 1A and form 1B), possessed in cyanobacteria. In most β-cyanobacteria, Rubisco is sequestered in the β-carboxysome lumen by a shell that is composed of shell and shell-associated proteins encoded by a ccmKLMNO operon (Omata et al., 2001; Long et al., 2010; Rae et al., 2012). The carboxysomal carbonic anhydrase is colocalized with Rubisco in the β-carboxysome, serving to create a CO2-rich microenvironment to favor the Rubisco activity. Some cyanobacterial species do not have the carboxysomal β-carbonic anhydrase (CcaA) homologs; instead, the N-terminal domain of CcmM functions as an active γ-carbonic anhydrase (Peña et al., 2010). The shell facets act as a selective barrier that allows the diffusion of HCO3− and retains CO2 in the interior (Dou et al., 2008). Through these mechanisms, carboxysomes elevate the CO2 concentration in the vicinity of Rubisco and thereby enhance the efficiency of carbon fixation. Supported by this nanoscale CO2-fixing machinery, cyanobacteria contribute more than 25% of global carbon fixation (Field et al., 1998; Liu et al., 1999). The efficiency of carboxysomes in enhancing carbon fixation has attracted tremendous interest in engineering the CO2-fixing organelle in other organisms. For example, introducing β-carboxysomes into higher plants that use the ancestral C3 pathway of photosynthesis could potentially enhance photosynthetic carbon fixation and crop production (Lin et al., 2014a, 2014b). However, engineering of functional carboxysomes requires extensive understanding about the principles underlying the formation of β-carboxysomes and the physiological integration of β-carboxysomes into the cellular metabolism. Indeed, cyanobacterial cells have evolved comprehensive systems to regulate the biosynthesis and spatial organization of carboxysomes, allowing them to modulate the capacity for photosynthetic carbon fixation. Recent studies elucidated that the β-carboxysome assembly is initiated from the packing of Rubisco enzymes, followed by the encapsulation of peripheral shell proteins (Cameron et al., 2013; Chen et al., 2013). In the model rod-shaped cyanobacterium Synechococcus elongatus PCC7942 (hereafter Synechococcus), three to four β-carboxysomes were observed to be evenly spaced along the centerline of the longitudinal axis of cells, ensuring the equal segregation of the machinery between daughter cells (Savage et al., 2010). Such specific organization of carboxysomes within cyanobacterial cells is likely to be determined by the interaction between carboxysomes and the cytoskeleton (Savage et al., 2010). Advanced understanding of the functions and assembly of β-carboxysome proteins has recently led to the construction of a chimeric protein that can functionally replace four native proteins (CcmM58, CcmM35, CcaA, and CcmN) required for carboxysome formation (Gonzalez-Esquer et al., 2015). These findings outlined the self-assembly nature and integration of carboxysomes in the cell. However, how β-carboxysome biosynthesis and organization are physiologically regulated in cyanobacteria in response to environmental changes remains poorly understood. Here, using a combination of live-cell confocal fluorescence microscopy and biochemical and physiological approaches, we investigated the formation and spatial positioning of β-carboxysomes in Synechococcus under varying light intensities. Our study provides new insights into the regulation of β-carboxysome biosynthesis by light and the roles of photosynthetic electron flow in the carboxysome assembly. Knowledge obtained from this work is fundamental to the bioengineering and modulation of functional carboxysomes to boost photosynthetic carbon fixation in dynamic and diverse environments

Effect of combinations of passive and active warming on muscle temperature and sprint performance

Muscle temperature (Tm) has a significant effect on muscle function, force and power production [1], hence the adoption of warm up procedures before power based events. In the majority of sprint or power based events there are periods of maximal activity interspersed with periods of low or no activity, during which Tm may decline, adversely affecting subsequent performance. We have previously shown that Tm will decline during 30 minutes of inactivity following the completion of a warm up, and that the use of passive external heating between warm up completion and sprint cycling performance reduces Tm decline and improves peak power output [2]. The aim of the present study was to follow on from our first Tm study and determine whether, apart from using the electrical heating between warm up and event, there is an additional benefit of using the electrical heating during warm up completion on muscle temperature and subsequent measures of sprint cycling performance. The secondary goal was to look at the efficacy of a redesigned heating system covering a larger area of muscle than in [2]

Acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults

Regular exercise-induced acute inflammatory responses are suggested to improve the inflammatory profile and insulin sensitivity. As body temperature elevations partly mediate this response, passive heating might be a viable tool to improve the inflammatory profile. This study investigated the acute, and chronic effects of hot water immersion on inflammatory and metabolic markers. Ten sedentary, overweight males (BMI: 31.0±4.2 kg/m2) were immersed in water set at 39°C for 1 h (HWI) or rested for 1 h at ambient temperature (AMB). Venous blood was obtained prior to, immediately post and 2 h post-session for assessment of monocyte intracellular heat shock protein 72 (iHsp72) and plasma concentrations of extracelullar heat shock protein 72 (eHsp72), interleukin-6 (IL-6), fasting glucose, insulin and nitrite. Thereafter, participants underwent a 2-week intervention period, consisting of 10 hot water immersion sessions (INT). Eight BMI-matched participants (BMI: 30.0±2.5 kg/m2) were included as control (CON). Plasma IL-6 and nitrite concentrations were higher immediately following HWI compared to AMB (IL-6 p<0.001, HWI: 1.37±0.94 to 2.51±1.49 pg/ml; nitrite p=0.04, HWI: 271±52 to 391±72 nM), while iHsp72 expression was unchanged (p=0.57). In contrast to resting iHsp72 expression (p=0.59), fasting glucose (p=0.04, INT: 4.44±0.93 to 3.98±0.98 mmol/l), insulin (p=0.04, INT: 68.1±44.6 to 55.0±29.9 pmol/l) and eHsp72 (p=0.03, INT: 17±41% reduction) concentrations were lowered after INT compared to CON. HWI induced an acute inflammatory response and increased nitric oxide bioavailability. The reductions in fasting glucose and insulin concentrations following the chronic intervention suggest that hot water immersion may serve as a tool to improve glucose metabolism

Do overweight and obese individuals demonstrate impaired thermoregulatory adaptation to six weeks of studio cycling training: a pilot study

High intensity interval training (HIIT) is effective at improving health markers in groups at risk of cardiovascular and metabolic disease. Studio cycling may offer a platform for HIIT in the community, however little is know about how increased adiposity influences thermal control during HIIT and the effect this may have on overweight patients who are new to exercise. The purpose of this pilot study was to investigate the thermal adaptation in response to studio based group HIIT in sedentary overweight adults