Hyperthermic fatigue precedes a rapid reduction of serum sodium and cramping in an ironman triathlete

We present two original observations. First, we document the attainment of a critically high internal body temperature in a triathlete performing in an Ironman triathlon that we believe directly influenced his ability to run fast. Second, this athlete experienced an unusually rapid reduction in blood sodium (Na+) that preceded cramping, despite presenting signs of dehydration

Hyperthermic Fatigue Precedes a Rapid Reduction in Serum Sodium in an Ironman Triathlete: A Case Report

Purpose: To monitor the hydration, core temperature, and speed (pace) of a triathlete performing an Ironman triathlon. Methods: A 35-year-old experienced male triathlete participated in the Western Australian Ironman triathlon on December 1, 2006. The participant was monitored for blood Na+ concentration before the race (PRE), at the transitions (T1 and T2), halfway through the run (R21), and after the race (POST; 2hPOST). Core body temperature (Tc; pill telemetry) was recorded continuously, and running speed (s3 stride sensor) was measured during the run. Results: The participant completed the race in 11 h 38 min, in hot conditions (26.6 ± 5.8°C; 42 ± 19% rel. humidity). His Tc increased from 37.0 to 38.6°C during the 57-min swim, and averaged 38.4°C during the 335-min bike (33.5 km·h−1). After running at 12.4 km·h−1 for 50 min in the heat (33.1°C), Tc increased to 39.4°C, before slowing to 10.0 km·h−1 for 20 min. Tc decreased to 38.9°C until he experienced severe leg cramps, after which speed diminished to 6 km·h−1 and Tc fell to 38.0°C. The athlete’s blood Na+ was constant from PRE to T2 (139–140 mEq·L−1, but fell to 131 mEq·L−1 at R21, 133 mEq·L−1 at POST, and 128 mEq·L−1 at 2hPOST. The athlete consumed 9.25 L of fluid from PRE to T2, 6.25 L from T2 to POST, and lost 2% of his body mass, indicating sweat losses greater than 15.5 L. Conclusion: This athlete slowed during the run phase following attainment of a critically high Tc and experienced an unusually rapid reduction in blood Na+ that preceded cramping, despite presenting with signs of dehydration

Implementing, monitoring and measuring a programme of relationship marketing

This single, embedded case study examined the marketing activities of Flensted Catering A/S, a Danish food company. The case is the first one in a series of case studies constituting a larger research project with the overall objective of understanding how to implement relationship marketing, how to monitor the outputs and how to measure the returns. In 1996, the company embarked on a three-phase programme directed at building relations with customers. As a prelude to the implementation, Flensted Catering A/S conducted focus groups and issued questionnaires to determine customer perceptions of how the company could meliorate its performance. Subsequently, the Danish firm established project teams, instituted customer-focused staff training and sought to improve communications with customers. Following the implementation, the monitoring revealed that Flensted Catering A/S was rated as a better supplier by 43 per cent of its customers and that customer retention had risen to 94 per cen

Are we being drowned in hydration advice? Thirsty for more?

Extreme Physiology and Medicine31Jan-1

Performance and physiological responses during a sprint interval training session: relationships with muscle oxygenation and pulmonary oxygen uptake kinetics

The purpose of this study was to examine the cardiorespiratory and muscle oxygenation responses to a sprint interval training (SIT) session, and to assess their relationships with maximal pulmonary O 2 uptake (VO 2pmax), on- and off-VO 2p kinetics and muscle reoxygenation rate (Reoxy rate). Ten male cyclists performed two 6-min moderate-intensity exercises (≈90-95% of lactate threshold power output, Mod), followed 10 min later by a SIT session consisting of 6 × 30-s all out cycling sprints interspersed with 2 min of passive recovery. VO 2p kinetics at Mod onset (VO 2p τon) and cessation (VO 2p τ off) were calculated. Cardiorespiratory variables, blood lactate ([La] b) and muscle oxygenation level of the vastus lateralis (tissue oxygenation index, TOI) were recorded during SIT. Percentage of the decline in power output (%Dec), time spent above 90% of VO 2p max (t > 90% VO 2p max) and Reoxy rate after each sprint were also recorded. Despite a low mean VO 2p (48.0 ± 4.1% of VO 2p max), SIT performance was associated with high peak VO 2p (90.4 ± 2.8% of VO 2p max), muscle deoxygenation (sprint ΔTOI = -27%) and [La] b (15.3 ± 0.7 mmol l -1) levels. Muscle deoxygenation and Reoxy rate increased throughout sprint repetitions (P 90% VO 2p max versus VO 2p τ off [r = 0.68 (90% CL, 0.20; 0.90); P = 0.03], there were no significant correlations between any index of aerobic function and either SIT performance or physiological responses [e.g., %Dec vs. VO 2p τ off: r = -0.41 (-0.78; 0.18); P = 0.24]. Present results show that SIT elicits a greater muscle O 2 extraction with successive sprint repetitions, despite the decrease in external power production (%Dec = 21%). Further, our findings obtained in a small and homogenous group indicate that performance and physiological responses to SIT are only slightly influenced by aerobic fitness level in this population

Effect of cold water immersion on repeated 1-km cycling performance in the heat

This study examined the effect of a short cold water immersion (CWI) intervention on rectal and muscle temperature, isokinetic strength and 1-km cycling time trial performance in the heat. Ten male cyclists performed a 1-km time trial at 35.0 ± 0.3 °C and 40.0 ± 3.0% relative humidity, followed by 20 min recovery sitting in either cold water (14 °C) for 5 min or in 35 °C air (control); a second 1-km time trial immediately followed. Peak and mean cycling power output were recorded for both time trials. Rectal and muscle temperature, and maximal isokinetic concentric torque of the knee extensors were measured before and immediately after the first and second time trials. Rectal temperature was not different between cold water immersion and control conditions at any time points. After the second time trial, however, muscle temperature was significantly lower (-1.3 ± 0.7 °C) in cold water immersion compared with the control trial. While peak and mean power decreased from the first to second time trial in both conditions (-86 ± 54 W and -24 ± 16 W, respectively), maximal isokinetic concentric torque was similar between conditions at all time points. The 5 min cold water immersion intervention lowered muscle temperature but did not affect isokinetic strength or 1-km cycling performance

Effect of a 5-min cold-water immersion recovery on exercise performance in the heat

Background: This study examined the effect of a 5-min cold-water immersion (14°C) recovery intervention on repeated cycling performance in the heat. Methods: 10 male cyclists performed two bouts of a 25-min constant-paced (254 (22) W) cycling session followed by a 4-km time trial in hot conditions (35°C, 40% relative humidity). The two bouts were separated by either 15 min of seated recovery in the heat (control) or the same condition with 5-min cold-water immersion (5th—10th minute), using a counterbalanced cross-over design (CP1TT1 → CWI or CON → CP2TT2). Rectal temperature was measured immediately before and after both the constant-paced sessions and 4-km timed trials. Cycling economy and Vo2 were measured during the constant-paced sessions, and the average power output and completion times were recorded for each time trial. Results: Compared with control, rectal temperature was significantly lower (0.5 (0.4)°C) in cold-water immersion before CP2 until the end of the second 4-km timed trial. However, the increase in rectal temperature (0.5 (0.2)°C) during CP2 was not significantly different between conditions. During the second 4-km timed trial, power output was significantly greater in cold-water immersion (327.9 (55.7) W) compared with control (288.0 (58.8) W), leading to a faster completion time in cold-water immersion (6.1 (0.3) min) compared with control (6.4 (0.5) min). Economy and Vo2 were not influenced by the cold-water immersion recovery intervention. Conclusion: 5-min cold-water immersion recovery significantly lowered rectal temperature and maintained endurance performance during subsequent high-intensity exercise. These data indicate that repeated exercise performance in heat may be improved when a short period of cold-water immersion is applied during the recovery period

Impairment of cycling capacity in the heat in well-trained endurance athletes after high-intensity short-term heat acclimation

10.1123/ijspp.2018-0537International Journal of Sports Physiology and Performance1481058 - 106

Effect of cold water immersion after exercise in the heat on muscle function, body temperatures, and vessel diameter

Cold water immersion and active recovery are common post-exercise recovery treatments. A key assumption about the benefits of cold water immersion is that it reduces inflammation in skeletal muscle. However, no data are available from humans to support this notion. We compared the effects of cold water immersion and active recovery on inflammatory and cellular stress responses in skeletal muscle from exercise-trained men 2, 24 and 48\ua0h during recovery after acute resistance exercise. Exercise led to the infiltration of inflammatory cells, with increased mRNA expression of pro-inflammatory cytokines and neurotrophins, and the subcellular translocation of heat shock proteins in muscle. These responses did not differ significantly between cold water immersion and active recovery. Our results suggest that cold water immersion is no more effective than active recovery for minimizing the inflammatory and stress responses in muscle after resistance exercise