Fiber type specific glycogen utilization in rat diaphragm during treadmill exercise

Abstract

To examine the significance of endogenous stores of glycogen in specific fiber types (I, IIa, IIb) of the costal region of the diaphragm, adult male Wistar rats performed continuous running (25 m/min, 8 degrees grade) exercise for either 30 min or until fatigue. At 30 min of exercise, glycogen loss, as measured microphotometrically using the periodic acid-Schiff technique averaged between 73 and 80% (P less than 0.05) in the different fiber types. When exercise was performed to exhaustion, representing an additional 94 min, no further reduction in glycogen was observed in any fiber type. Biochemical determinations of glycogen from the diaphragm confirmed the extensive reduction in glycogen concentration with exercise. Large reductions (P less than 0.05) in glycogen were also noted in the soleus, plantaris, and vastus lateralis red. Although significant depletion (P less than 0.05) occurred in the vastus lateralis white, it was not as pronounced as in these other muscles. Repletion to preexercise glycogen concentration was complete by 4 h of recovery in all muscles except the vastus lateralis white. It is concluded that endogenous glycogen is a significant substrate in all muscles sampled regardless of fiber composition. In the case of the costal region of the diaphragm, the increased work of breathing resulting from heavy exercise leads to the recruitment of all fiber types, and each fiber type depends on glycogen as a substrate at least early in the exercise.

How Important Is the Differentiation between Apnea and Hypopnea?

“…After application of an exhaustive load on the RP, acute deple tion of glycogen has been demonstrated [98][99][100]. During the recovery period, restoration of the glycogen reservoir takes about 4 h in the rat diaphragm [100]. These data are consistent with our hypothesis that during the unloading time of the RP by mechanical ventilation, sleep and for LTOj, the glycogen reservoirs in the respiratory muscles are refilled.…”

“…The associated chronic hypoxemia results in an expression of glucose transport proteins in the diaphragm [97], If more power is necessary (e.g. during physical activity or increased load due to an asthma attack) the muscle cell can consume its own glycogen stores [98][99][100], Glycogen enables a greater performance of work of breathing for several hours. After application of an exhaustive load on the RP, acute deple tion of glycogen has been demonstrated [98][99][100].…”

Impact of endurance concentric contraction training on acute force deficit following in vitro lengthening contractions

“…This evidence comes from studies reporting significant increases in oxidative enzyme activity following training (Gosselin et al 1992;Powers et al 1992Powers et al , 1994, increased oxygen consumption by the respiratory muscles (Aaron et al 1992), increased diaphragm blood flow (Laughlin and Armstrong 1982), increased diaphragm muscle oxygen extraction, increased glycogen utilization (Green et al 1987), as well as changes in myosin heavy chain isoform composition . However, the diaphragm is not thought to undergo any lengthening phase during normal exercise ventilation (Easton et al 1989(Easton et al , 1999Wakai et al 1994;Reid and MacGowan 1998), making it ideal for examining the effect of concentric-only muscle contraction endurance training on muscle injury protection following lengthening contractions.…”

Missverständliche Empfehlung

“…Die intermittierenden Perioden der kompletten Entlastung der Atemmuskulatur bewirken eine Regeneration der zellulären Glykogenspeicher und wirken somit einer chronischen Ermüdung der Muskulatur entgegen, die aus der vermehrten Atemarbeit bei dauerhafter -auch unterstützter -Spontanatmung resultieren kann [3]. Tierexperimentelle Daten konnten zeigen, dass die energetische Regeneration des Zwerchfells etwa 3-4 h benötigt [4,5].…”