Nicola Gerrett

Reducing muscle temperature drop after warm-up improves sprint cycling performance

PURPOSE This study aimed to determine the effect of passive insulation versus external heating during recovery after a sprint-specific warm-up on thigh muscle temperature and subsequent maximal sprint performance. METHODS On three separate occasions, 11 male cyclists (age = 24.7 ± 4.2 yr, height = 1.82 ± 0.72 m, body mass = 77.9 ± 9.8 kg; mean ± SD) completed a standardized 15-min intermittent warm-up on a cycle ergometer, followed by a 30-min passive recovery period before completing a 30-s maximal sprint test. Muscle temperature was measured in the vastus lateralis at 1, 2, and 3 cm depth before and after the warm-up and immediately before the sprint test. Absolute and relative peak power output was determined and blood lactate concentration was measured immediately after exercise. During the recovery period, participants wore a tracksuit top and (i) standard tracksuit pants (CONT), (ii) insulated athletic pants (INS), or (iii) insulated athletic pants with integrated electric heating elements (HEAT). RESULTS Warm-up increased Tm by approximately 2.5 °C at all depths, with no differences between conditions. During recovery, Tm remained elevated in HEAT compared with INS and CONT at all depths (P < 0.001). Both peak and relative power output were elevated by 9.6% and 9.1%, respectively, in HEAT compared with CONT (both P < 0.05). The increase in blood lactate concentration was greater (P < 0.05) after sprint in HEAT (6.3 ± 1.8 mmol·L(-1)) but not INS (4.0 ± 1.8 mmol·L(-1)) versus CONT (4.1 ± 1.9 mmol·L(-1)). CONCLUSIONS Passive heating of the thighs between warm-up completion and performance execution using pants incorporating electrically heated pads can attenuate the decline in Tm and improve sprint cycling performance.

Female thermal sensitivity to hot and cold during rest and exercise

Regional differences in thermal sensation to a hot or cold stimulus are often limited to male participants, in a rested state and cover minimal locations. Therefore, magnitude sensation to both a hot and cold stimulus were investigated during rest and exercise in 8 females (age: 20.4 ± 1.4 years, mass: 61.7 ± 4.0 kg, height: 166.9 ± 5.4 cm, VO2max: 36.8 ± 4.5 ml·kg(-1)·min(-1)). Using a repeated measures cross over design, participants rested in a stable environment (22.3 ± 0.9°C, 37.7 ± 5.5% RH) whilst a thermal probe (25 cm(2)), set at either 40°C or 20°C, was applied in a balanced order to 29 locations across the body. Participants reported their thermal sensation after 10s of application. Following this, participants cycled at 50% VO2max for 20 min and then 30% VO2max whilst the sensitivity test was repeated. Females experienced significantly stronger magnitude sensations to the cold than the hot stimulus (5.5 ± 1.7 and 4.3 ± 1.3, p<0.05, respectively). A significant effect of location was found during the cold stimulation (p<0.05). Thermal sensation was greatest at the head then the torso and declined towards the extremities. No significant effect of location was found in response to the hot stimulation and the pattern across the body was more homogenous. In comparison to rest, exercise caused a significant overall reduction in thermal sensation (5.2 ± 1.5 and 4.6 ± 1.7, respectively, p<0.05). Body maps were produced for both stimuli during rest and exercise, which highlight sensitive areas across the body.

The effect of ice slurry ingestion on intermittent activity and a run to exhaustion in the heat

Major competitions are often staged in hot environments. However, the bodys ability to dissipate heat is compromised during heat stress resulting in a concomitant rise in core temperature (Tc), ultimately leading to impaired performance. Precooling methods such as ice vests and cold water immersion are employed before competition, to lower Tc and increase heat storage before a critical Tc is reached. However, there are numerous practical limitations meaning pre-existing methods are impractical for use in a field setting. Ice slurry ingestion has been investigated as a more practical precooling method and has enhanced endurance performance [1], however research has yet to determine its effects upon intermittent activity. Therefore the aim of this study was to determine the efficacy of ice slurry ingestion as a precooling method prior to intermittent activity and a run to exhaustion in the heat.

Sweat from gland to skin surface – production, transport and skin absorption

By combining galvanic skin conductance (GSC), stratum corneum hydration (HYD) and regional surface sweat rate (RSR) measurements at the arm, thigh, back and chest, we closely monitored the passage of sweat from gland to skin surface. Through a varied exercise-rest protocol, sweating was increased slowly and decreased in 16 male and female human participants (25.3 ± 4.7 yr, 174.6 ± 10.1 cm, 71.3 ± 12.0 kg, 53.0 ± 6.8 ml·kg-1·min-1). ∆GSC and HYD increased before RSR, indicating pre-secretory sweat gland activity and skin hydration. ∆GSC and HYD typically increased concomitantly during rest in a warm environment (30.1 ± 1.0°C, 30.0 ± 4.7% relative humidity) and only at the arm did ∆GSC increase before an increase in HYD. HYD increased before RSR, before sweat was visible on the skin, but not to full saturation, contradicting earlier hypotheses. Maximal skin hydration did occur, as demonstrated by a plateau in all regions. Post exercise rest resulted in a rapid decrease in HYD and RSR but a delayed decline in ∆GSC. Evidence for reabsorption of surface sweat into the skin following a decline in sweating, as hypothesized in the literature, was not found. This suggests that skin surface sweat, after sweating is decreased, may not diffuse back into the dermis, but is only evaporated. These data, showing distinctly different responses for the three measured variables, provide useful information about the fate of sweat from gland to surface that is relevant across numerous research fields (e.g., thermoregulation, dermatology, ergonomics and material design). NEW & NOTEWORTHY After sweat gland stimulation, sweat travels through the duct, penetrating the epidermis before appearing on the skin surface. We found that only submaximal stratum corneum hydration was required before surface sweating occurred. However, full hydration occurred only once sweat was on the surface. Once sweating reduces, surface sweat evaporation continues, but there is a delayed drying of the skin. This information is relevant across various research fields, including environmental ergonomics, dermatology, thermoregulation, and skin-interface interactions.

Distribution of skin thermal sensitivity

The chapter explores measurement techniques to investigate thermal sensitivity of the skin across numerous locations over the body. Different definitions of thermal sensitivity are provided which will inform the method of stimulation. Techniques of stimulating the skin are proposed (e.g., thermal peltier probe, water-perfused suit, or patches), and temperature, surface area, and duration are discussed. Sensitivity can be assessed immediately (transient) or after a given period of time (steady state), and data can be presented in a variety of forms. The chapter proposed presenting the data as body maps to add clarity for the reader and examples are provided.

Female skin conductance and regional differences in thermal sudomotor activity at rest and during exercise in different environments

Female skin conductance and regional differences in thermal sudomotor activity at rest and during exercise in different environmentsIntroduction: The motor activities contribute to the child’s educational process1 , promote the prevention of many diseases2 and promote the development of self-efficacy perceived 3. In the Apulia region to 39,2% of children of 8 years has excess weight (2010) 4; targeted interventions are needed to counteract the sedentary habits5 ; reduce body weight and increase the self-perception, through a wide repertoire of motor activities. Methods: It has been carried out an intervention of extracurricular physical activities for 6 months. Motor test have been proposed (T0 vs T1)6: standing long jump; 20-m speed; 1 Kg medicine ball throw; the self-report: Perceived Physical Ability Scale for Children (PPAS_C)7 to 28 children divided into overweight and obese according to cutt off of Cole8, attending primary school (F = 12; age: M ± ds = 9.76 ± 0.84; BMI: M ± ds = 24,28 ±2,13; M = 16; age: M ± ds = 9.20 ± 1.54; BMI M±ds 27,60±4.07). Results: Apart from the descriptive statistics, it was carried out the ANOVA 2 analysis of the variance (test: T0 vs T1) x 2 (sex) repeating the measurements for the last factor, in order to highlight the significant differences related to the dependent variables taken into consideration. The significativity index was set to p< 0,05. Some differences emerged with respect to the test-retest within the tests: standing long jump (Female: p = 0,003; Male, p = 0,001); 1 Kg medicine-ball throw (Female: p = 0,02; Male: p =0,003); in the scale of PPAS_C (Female: p = 0,000; Male: p = 0.04). We highlight gender differences in the standing long jump: females have higher performance than males (p = 0,02); in the scale of PPAS_C not show differences. Males and females show a reduction in BMI (T0 vs T1 ): F: M ± ds = 24,28 ±2,13 vs 23,39± 2,03; M: 27,60±4,07 vs 27,38 ± 4,18. Conclusion: The study found positive effects on levels of motor performance and physical self-perception after the program extracurricular. The experiences of success, measured in terms of increased motor abilities of real and perceived, are essential to prevent childhood overweight. Recent studies have shown that physical activity interventions, combined with healthy eating habits, at school and in extracurricular, can reduce children’s BMI9. References 1. Bailey R (2006), JSH,76, 397-401 2. Brambilla P et al. (2010), Int J Obes , 35,16-28 3. Feltz DL et al (2008), Champaign, IL: HK 4. http://www.epicentro.iss.it/territorio/puglia.asp 5. Biddle SJH et al. (2011), Br J Sports Med, 45, 937-942 6. Morrow JR et al. (2005), Champaign, IL: HK 7. Colella D et al. (2008), SBP, 36,841-8 8. Cole TJ et al. (2000), BMJ, 320,1240-3 9. Lavelle HV et al.(2012), J Public Health, 20,1-10 The psychobiosocial state inventory: preliminary evidence of factorial validity