Environmental heat stress, hyperammonemia and nucleotide metabolism during intermittent exercise

Abstract

This study investigated the influence of environmental heat stress on ammonia (NH3) accumulation in relation to nucleotide metabolism and fatigue during intermittent exercise. Eight males performed 40 min of intermittent exercise (15 s at 306+/-22 W alternating with 15 s of unloaded cycling) followed by five 15 s all-out sprints. Control trials were conducted in a 20 degrees C environment while heat stress trials were performed at an ambient temperature of 40 degrees C. Muscle biopsies and venous blood samples were obtained at rest, after 40 min of exercise and following the maximal sprints. Following exercise with heat stress, the core and muscle temperatures peaked at 39.5+/-0.2 and 40.2+/-0.2 degrees C to be approximately 1 degrees C higher (P<0.05) than the corresponding control values. Mean power output during the five maximal sprints was reduced from 618+/-12 W in control to 558+/-14 W during the heat stress trial (P<0.05). During the hot trial, plasma NH3 increased from 31+/-2 microM at rest to 93+/-6 at 40 min and 151+/-15 microM after the maximal sprints to be 34% higher than control (P<0.05). In contrast, plasma K+ and muscle H+ accumulation were lower (P<0.05) following the maximal sprints with heat stress compared to control, while muscle glycogen, CP, ATP and IMP levels were similar across trials. In conclusion, altered levels of "classical peripheral fatiguing agents" does apparently not explain the reduced capacity for performing repeated sprints following intermittent exercise in the heat, whereas the augmented systemic NH3 response may be a factor influencing fatigue during exercise with superimposed heat stress.

Salbutamol effects on systemic potassium dynamics during and following intense continuous and intermittent exercise

“…This is the first report of arterial [K + ] during HI int , comprising brief sprints repeated in bursts to simulate intense activity undertaken in many team sports (Bishop et al 2011 (Krustrup et al 2006;Wylie et al 2013;Mohr et al 2011;Mohr et al 2007;Duffield and Marino 2007;Mohr et al 2006;Struthers et al 1988). …”

“…The antecubital venous [K + ] reported during intense intermittent exercise varies, reaching 4.3 mM during squash (Struthers et al 1988), 5.1 mM during soccer (Krustrup et al 2006), and 5.5-6 mM during repeated intermittent sprint testing (Wylie et al 2013;Mohr et al 2011;Mohr et al 2007;Duffield and Marino 2007;Mohr et al 2006 O 2 peak for use on the same cycle ergometer in the subsequent experimental trials. All respiratory measurements were as previously described (Atanasovska et al 2014) .…”

Thermoregulation in elite athletes

“…Other neurotransmitters such as glutamate and g-aminobutyric acid may be affected as a consequence of the increased ammonia concentrations associated with heat stress [21 ]. These changes may be compounded by alterations in permeability of the blood-brain barrier also associated with hyperthermia [22].…”

Fatigue and Recovery in Soccer: Evidence and Challenges

“…During a soccer game, the average core temperature ranges between 39.0 and 39.5ºC [18,41] whereas muscle temperature has previously been shown to be 0.5-1ºC lower [42]. The hyperthermic state may accelerate the degradation of purine nucleotides and/or catabolism of amino acids with concomitant hyperammonemia, which has been linked to central fatigue [43,44].…”