Glycogen Utilization in Leg Muscles of Men during Level and Uphill Running

Abstract Glycogen depletion was followed in the soleus, gastrocnemius, and vastus lateralis muscles of 3 men during 2 h of treadmill running on the level and uphill (+6 o ). One subject also ran downhill (‐4.5 o ). Running speed was adjusted in each condition to require 75% of the subjects' Vo 2 max. Glycogen concentrations were similar in all 3 muscles at rest. From PAS staining glycogen appeared to be evenly distributed between slow and fast twitch fibres. A glycogen depletion of 17, 33, and 44 mmol of glucose units X kg ‐1 wet weight occurred in the vastus lateralis, soleus, and gastrocnemius muscles, respectively, after running on the level. These values were 55, 46, and 60 mmol X kg ‐1 , respectively, after uphill running. Glycogen depletion in the soleus and gastrocnemius muscles after downhill running was similar to that after running on the level, however, in the vastus lateralis it was intermediate to that for uphill and level running. A loss of PAS stain was observed first in the slow twitch fibres in all conditions. The results support the concept of a differential involvement of the leg muscles during running which can be modified by running either uphill or downhill. Thus it is of importance for the representativity of a sample that it is taken from a particular muscle when the local response to exercise or physical training is studied.