Glykogentillgänglighetens påverkan på SR Ca2+

[King Grub]

Little is known about the precise mechanism that relates skeletal muscle glycogen to muscle fatigue. The aim of the present study was to examine the effect of glycogen on sarcoplasmic reticulum (SR) function in the arm and leg muscles of elite cross-country skiers (n=10, V O2 max 72±2 ml . kg-1 min-1) before, immediately after, and 4h and 22h after a fatiguing 1h ski race. During the first 4hrs recovery, skiers received either water or carbohydrate (CHO) and thereafter all received CHO enriched food. Immediately after the race, arm glycogen was reduced to 31±4% and SR Ca2+ release rate decreased to 85±2% of initial levels. Glycogen noticeably recovered after 4h recovery with CHO (59±5% initial) and the SR Ca2+ release rate returned to pre-exercise levels. However, in the absence of CHO during the first 4h recovery, glycogen and the SR Ca2+ release rate remained unchanged (29±2% and 77±8%, respectively), with both parameters becoming normal after the remaining 18h recovery with CHO. Leg muscle glycogen decreased to a lesser extent (71±10% initial), with no effects on the SR Ca2+ release rate. Interestingly, transmission electron microscopy (TEM) analysis revealed that the specific pool of intramyofibrillar glycogen, representing 10-15% total glycogen, was highly significantly correlated with the SR Ca2+ release rate. These observations strongly indicate that low glycogen and especially intramyofibrillar glycogen, as suggested by TEM, modulate the SR Ca2+ release rate in highly trained subjects. Thus, low glycogen during exercise may contribute to fatigue by causing a decreased SR Ca2+ release rate.

J Physiol. 2010 Dec 6. Role of glycogen availability on SR Ca2+ kinetics in human skeletal muscle.

[Apos78]

Nu var det här topptränade skidåkare men det skulle vara intressant att se vid vilken intensitet/duration som detta blir av betydelse vid träning på mer normala nivåer. Om ens alls.

[Bozar]

Bekräftar ju tesen som länge funnits att kolhydrat-supplement har betydande effekt på återinlagring av glykogen.

Sen är det som Apos78 skriver frågan om det har betydelse för vanliga motionärer som inte tömmer glykogen-depåerna i samma omfattning, kommer aktiviteten i SR proteinet påverkas i någon betydelsefull omfattning? Jag tycker det är väl tidigt att fatta den slutsatsen men upplägget är ju bra så om de upprepade studien med "vanliga" människor så skulle det ge mer trovärdiga resultat.