Effect of eccentric exercise with reduced muscle glycogen on plasma interleukin-6 and neuromuscular responses of m. quadriceps femoris.

Abstract

Eccentric exercise can result in muscle damage and interleukin-6 (IL-6) secretion. Glycogen availability is a potent stimulator of IL-6 secretion. We examined effects of eccentric exercise in a low glycogen state on neuromuscular function and plasma IL-6 secretion. Twelve active males (23 ± 4 years, 179 ± 5 cm, 77 ± 10 kg) completed two downhill treadmill runs (gradient, -12%, 5x8 min; speed, 12.1 ± 1.1 km∙h-1) with normal (NG) and reduced muscle glycogen (RG) in randomized order and at least six weeks apart. Muscle glycogen was reduced using an established cycling protocol until exhaustion and dietary manipulation the evening before the morning run. Physiological responses were measured up to 48 h after the downhill runs. During recovery, force deficits of m. quadriceps femoris by maximal isometric contractions were similar. Changes in low-frequency fatigue were larger with RG. Voluntary activation and plasma IL-6 levels were similar in recovery between conditions. It is concluded that unaccustomed, damaging eccentric exercise with low muscle glycogen of the m. quadriceps femoris: i) exacerbated low-frequency fatigue, but ii) had no additional effect on IL-6 secretion. Neuromuscular impairment after eccentric exercise with low muscle glycogen appears to have a greater peripheral component in early recovery.