h z G b T R i j n i , J., L. HERMAXSEK;, E. HULTMAN a n d B. &\LrIN. Diet, mus& ghcogeii a i d p l y i c a l perJi,rmance. Xcta physiol. scand. 1967. 71. 1-10---150. 'l'hc m i i s c l r glycogen content of the quadriccps fcnioris m u s c l e was tlrtcrniincd in 9 I l t d i l i y 5111)jects \\ith the aid of t h r needlr biopsy technique. T h e glycogcn contvnt could br varird in th,.individual subjects by instituting diffcrcrit dicts after rxhatistion of the glycogen stow I>>-hartl cxrrcisc. Thus. the gl>-cogen contcnt aftcr a fat 1 protein ( P ) and a carbohydrate-rich C:J c1iC.t varird maximally from 0.6 g 100 g musclc to 4.7 g . I n all suhjrcts. t h r glycogen content aftcr tlic Cl diet Tvas higher than thr normal range for mriscle glycogen. drtermincd aftcr the mixed ~ 11) dict..iftrr each dirt prrincl. t h r subjects \vorked on a bicycle crgomctcr at a \vork load cirrrspondinq t o 71, pi'r cent of their maximal O L uptake. to complete exhaustion. 'l'he avcragr ivork time \va> -19. 126 and 189 min after diets P, .\I and C:; and a good correlation was noted bct\vren \\t,rk tinit. and rhr initial musclc glycogen content. T h e total carbohydrate utiliation during thr n~~r k prriotls 798 g : was well correlated to the decrease in glycogen contrnt. I t is thrrefbrr coricltidcd that thr g1)cogt:n content of the \\orking musclc is a determinant for thr capacity to prrforni Icinq-[crm heavy cxercisc. hlorru\-rr. it has Iwrn shoivn that thr glycogen content and, conseqrirntl long-trrni w o r k capacity can be appreciably varied by inskitlttinS diEcrrnt diets aftrr $1) dcijl c,tio 11. i 4

HERMANSEN, I-., E. HULTMAN and B. SALTIN. Muscle glycogen during prolonged severe exercise. Acta physiol. scand. 1967. 71. 129-139. 10 well trained and 10 untrained subjects worked to complete exhaustion on a bicycle ergometer with work loads averaging 77 (76-87) per cent of their individual maximal aerobic power. Determinations of glycogen used by working muscles (biopsy of lateral portion of the quadriceps femoris muscles) and of combusted carbohydrate (Vos and R Q ) were performed at certain intervals from the start of work to exhaustion. At a combustion rate of about 3 g carbohydrate per minute ( R Q around 0.9 or higher) and at average values for glycogen in resting muscle of 1.6 (1.1-2.5)g/lOO wet muscle, the effective work time was around 85 min for the untrained and 90 min for the trained subjects At the end of the exhaustive exercise the glycogen content averaged 0.06 g in the untrained and 0.12 g/100 g wet muscle in the trained subjects. A close relationship between utilized glycogen and combusted carbohydrate was found, and it seems highly probable that at high relative workloads primarily the glycogen stores in the exercising muscles will limit the capacity for prolor ged strenuous work. 673003. Acia plysiol. scand. VoE. 71: 2-3 1-

Intramuscular fluid pressures were recorded in the vastus medialis of seven healthy male volunteers. Pressures were measured simultaneously at three different sites in the muscle by a catheter-tip transducer with extremely low volume-displacement characteristics and by two extracorporeal transducers connected to slit catheters. All three recording systems gave qualitatively similar results provided the catheters had inner diameters exceeding 0.53 mm and allowed measurement of pressures lasting as short as 1 s. Wick catheters yielded slower responses than slit catheters. At any position intramuscular fluid pressure increased linearly with force up to maximal voluntary contraction (MVC). However, slopes of these curves varied greatly mainly because the pressure was also a linear function of the distance from the fascia. The highest recorded pressure was 570 Torr. At prolonged submaximal contractions intramuscular fluid pressure oscillated independent of contraction force. The linearity of both the pressure-force relationship and the pressure-depth relationship is compatible with a simple model based on the law of Laplace because the muscle fibers are curved during contraction in this muscle. It is hypothesized that blood flow is first compromised deep in the muscle where pressure is highest and in general at lower stress or tension in short bulging muscles with great curvature of the fibers compared with long slender ones.

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Muscle fiber diameters and numbers of capillaries per fiber, per square millimeter, and around each fiber were determined in needle biopsies from the lateral part of the quadriceps muscle of 23 young men. Twelve subjects were untrained (UT) and eleven were endurance-trained (ET) athletes. Average values for maximal oxygen uptake were 51.3 (UT) and 72.0 ml/kg-min (ET). Mean fiber diameters were not significantly different in the two groups (48.8 and 49.1 micron). The capillaries per fiber ratios were 1.77+/-0.10 and 2.49+/-0.08 (mean+/-SE) in the UT and ET groups, respectively. The numbers of capillaries around each fiber were 4.43+/-0.19 (UT) and 5.87+/-0.18 (ET). The numbers of capillaries per mm2 were 585+/-40 (UT) and 821+/-28 (ET). Fiber diameters were 28% smaller in ultrathin than in fresh-frozen sections from the same biopsies. After correction for this difference, the numbers of capillaries per mm2 were 305 and 425 in the UT and ET, respectively. The capillaries per fiber ratio increased with increasing fiber diameter, but not sufficiently to maintain the number of capillaries per mm2. Fibers containing many mitochondria are surrounded by more capillaries than fibers with few mitochondria.

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