Glucose Infusion Attenuates Muscle Fatigue in Rat Plantaris Muscle During Prolonged Indirect Stimulation in Situ

Abstract

showed that ingestion of a glucose polymer (1.8 g min _1 ) increased exercise time from 192 to 252 min during cycling at 70 % of the maximum rate of oxygen uptake (◊J ,max ). In the study by McConell et al. (1999) exercise time at 69 % ◊J ,max increased from 152 to 199 min with ingestion of 287 g CHO. This phenomenon has also been described in animals (Dill et al. 1932; Bagby et al. 1978; Slentz et al. 1990). For instance, in the study by Slentz et al. (1990) running time to exhaustion, at 8 % gradient and 30 m min _1 , increased from 180 to 276 min in rats following administration of 1.44 g CHO. In addition, the ability to perform resistance exercise could also increase when CHO is ingested (Lambert et al. 1991;Haff et al. 2001). In the study by Haff et al. (2001), ingestion of 240 g CHO before and during intermittent isokinetic leg exercise significantly increased the total amount of work performed from 38.1 to 41.1 kJ.The effect of CHO ingestion on exercise time to exhaustion during prolonged exercise and on the ability to perform resistance exercise could be due to several factors including (1) an increased contribution of plasma glucose oxidation to the energy yield (Coyle et al. 1986), (2) muscle glycogen sparing (Tsintzas et al. 1996), (3) maintenance of blood glucose concentration, which could delay central fatigue (Davis et al. 1992) and has been shown to improve cognitive performance (Collardeau et al. 2001), (4) an increase in the exercise-induced activation of muscle pyruvate dehydrogenase (Tsintzas et al. 2000), (5) an attenuation of muscle and plasma ammonia accumulation (Snow et al. 2000) and (6) an improved muscle energy balance (McConnell et al. 1999). However, the mechanism(s), which could mediate improvements in exercise performance, associated with CHO administration : plasma glucose 11 ± 1.1, vs. 4.9 ± 0.2 mM with infusion of saline) (8 rats per group). Glucose infusion attenuated the reduction in submaximal peak dynamic force (55 % decrease vs. 70 % decrease in rats infused with saline alone, P < 0.05). In a third group of rats (n = 8), infusion of glucose 30 min after the start of stimulation partially restored submaximal peak dynamic force (P < 0.05). Maximum dynamic and isometric forces at the end of the period of stimulation were also higher (P < 0.05) in rats infused with glucose (4.0 ± 0.2 and 4.3 ± 0.2 N, respectively) than saline alone (3.0 ± 0.2 and 3.5 ± 0.2 N, respectively). The beneficial effect of glucose infusion on peripheral muscle force during prolonged stimulation was not associated with a reduction in muscle glycogen utilisation, nor with a reduction of fatigue at the neuromuscular junction, as assessed through maximal direct muscle stimulation (200 Hz for 200 ms; 150 V; pulse width, 0.05 ms). However, changes in M-wave peak-to-peak amplitude, duration and total area suggest that glucose infusion, and/or the associated increase in plasma insulin concentration, may prevent the deterioration of electrical properties of the muscle fibre membrane. Experimental Physiology (2...

Glucose infusion attenuates fatigue without sparing glycogen in rat soleus muscle during prolonged electrical stimulation in situ

“…We have shown that glucose infusion attenuated muscle fatigue in the rat plantaris muscle stimulated indirectly for 60 min in situ (Karelis et al 2002). This was not associated with any reduction in muscle glycogen utilization, which is consistent with data from Tsintzas et al (1995Tsintzas et al ( , 1996Tsintzas et al ( , 2001 since the plantaris muscle is predominantly composed of type II fibres (Delp and Duan 1996).…”

“…The beneficial effect of glucose infusion on dynamic force during prolonged indirect stimulation, however, was not associated with any improvement in twitch force. Karelis et al (2002) also reported a beneficial effect of glucose infusion on dynamic force in the rat plantaris muscle indirectly stimulated in situ. However, when saline was infused the reduction in dynamic force was larger (70%) than that seen in the current experiment (45%).…”

Reduced Muscle Glycogen Differentially Affects Exercise Performance and Muscle Fatigue

“…It also raises the possibility that the hypoglycemia experienced by the LG animals during exercise may have induced some degree of peripheral fatigue during treadmill exercise. However, in the Karelis et al [24] study, plasma glucose levels were very high during infusion, nearly twice the initial and control levels and, in the control condition, there was no decline in blood glucose. Further, the slight hypoglycemia experience by the LG animals during stimulation (present study) was not associated with alterations in force or fatigue.…”

“…It should be pointed out that Karelis et al [24] showed that glucose infusion during in situ stimulation attenuated the extent of fatigue and partially restored force in fatigued muscle, possibly by maintaining Na/K pump function. is suggests that blood glucose may have a direct effect on muscle function during fatiguing exercise.…”

Efecto de los nucleótidos CMP y UMP en la fatiga en ratas

“…In these experiments we observed that, before exercise, rats treated with CMP/UMP had significantly higher muscle glucose concentrations compared to nontreated rats. A possible explanation is that rats treated with CMP/UMP undergoes an adaptation state, which allows them to store higher levels of glucose in muscle, and can, therefore, endure more exercise (21,28). One way of favoring the entry of glucose in the cells is up regulating the glucose transporters present in the cell membrane such as the GLUT family (22).…”