release channel (CRC), causing the channel to open. To further examine the effects of AgNO 3 on the CRC and the Ca 2ϩ -ATPase, Ca 2ϩ release was measured in muscle homogenates prepared from rat hindlimb muscle using indo 1. Cyclopiazonic acid (CPA) and ruthenium red (RR) were used to inhibit the Ca 2ϩ -ATPase and block the CRC, respectively, before inducing Ca 2ϩ release with both AgNO3 and 4-chlorom-cresol (4-CMC), a releasing agent specific for the CRC. With AgNO3 and CPA, the early rapid rate of release (phase 1) was increased (P Ͻ 0.05) by 42% (314 Ϯ 5 vs. 446 Ϯ 39 mol ⅐ g protein Ϫ1 ⅐ min Ϫ1 ), whereas the slower, more prolonged rate of release (phase 2) was decreased (P Ͻ 0.05) by 72% (267 Ϯ 39 vs. 74 Ϯ 7.7 mol ⅐ g protein Ϫ1 ⅐ min Ϫ1 ). RR, in combination with AgNO3, had no effect on phase 1 (P Ͼ 0.05) (314 Ϯ 51 vs. 334 Ϯ 43 mol ⅐ g protein Ϫ1 ⅐ min Ϫ1 ) and decreased phase 2 (P Ͻ 0.05) by 65% (245 Ϯ 34 vs. 105 Ϯ 8.2 mol ⅐ g protein Ϫ1 ⅐ min Ϫ1 ). With 4-CMC, CPA had no effect (P Ͼ 0.05) on either phase 1 or 2. With addition of RR, phase 1 was reduced (P Ͻ 0.05) by 59% (2,468 Ϯ 279 vs.

In order to determine the influence of an extensive history of participation in high intensity activity on muscle fiber type, fiber size, and metabolic profile, elite ice hockey players were selected for investigation from three different leagues. Biopsy samples from the vastus lateralis muscle were obtained from different groups of players prior to and following the season and compared with control subjects. No significant differences were found in the percentage (49.6 vs. 43.8%) or the size of the ST fibers between the elite athletes and the control group, nor was there any significant alteration following the season of play in these variables. For the FT fiber subgroups, a reduction in the FTb (12.2 vs. 3.9%) and an increase in FTa (38.0 to 45.2%) fiber populations occurred over the season. Similarly, increases in fiber area were observed for both FT subgroups pre to post season. Of the enzymes studied only 3-hydroxyacyl CoA dehydrogenase was elevated in the post season measures, while total phosphorylase and phosphofructokinase were significantly lower. The metabolic pattern exhibited does not appear to be substantially different from what would be expected from an untrained group of similar fiber distribution.

It is concluded that in crude homogenates, SR Ca2+-uptake and Ca2+-ATPase activity are elevated in recovery following prolonged running and that the elevation in these properties is more pronounced during passive compared with active recovery.

To examine the hypothesis that foot-strike hemolysis alters vascular volumes and selected hematological properties is trained athletes, we have measured total blood volume (TBV), red cell volume (RCV) and plasma volume (PV) in cyclists (n = 21) and runners (n = 17) and compared them to those of untrained controls (n = 20). TBV (ml x kg(-1)) was calculated as the sum of RCV (ml x kg(-1)) and PV (ml x kg(-1)) obtained using 51Cr and 125I-labelled albumin, respectively. Hematological assessment was carried out using a Coulter counter. Peak aerobic power (VO2peak) was measured during progressive exercise to fatigue using both cycle and treadmill ergometry. RCV was 15% higher (P < 0.05) in male cyclists [35.4 (1.0), mean (SE); n = 12] and runners [35.3 (0.98); n = 9] compared to the controls [30.7 (0.92); n = 12]. Similar differences existed between the female cyclists [28.2 (2.1); n = 9] and runners [28.4 (1.0); n = 8] compared to the untrained controls [24.9 (1.4); n = 8]. For the male athletes, PV was between 19% (cyclists) and 28% (runners) higher (P < 0.05) in the trained athletes compared to the untrained controls. The differences in PV between the female groups were not significant. Although the males had a higher (P < 0.05) TBV, RCV and PV than the females, no differences between cyclists and runners were found for either gender. Mean cell volume was not different between the athletic groups. VO2peak (ml x kg(-1) x min(-1)) was higher (P < 0.05) in both male [68.4 (1.5)] and female [54.8 (2.1)] runners when compared to the untrained males [47.1 (1.0)] and females [40.5 (2.1)]. Although differences existed between the genders in VO2peak for both cyclists and runners, no differences were found between the athletic groups within a gender. Since the vascular volumes were not different between cyclists and runners for either the males or females, foot-strike hemolysis would not appear to have an effect on that parameter. The significant correlations (P < 0.05) found between VO2peak and RCV (r = 0.64 and 0.64) and TBV (r = 0.82 and 0.63) for the males and females, respectively, suggests a role for the vascular system in realizing a high aerobic power.

SUMMARY1. The effects of prolonged exercise on energy metabolism in type I and type II muscle fibres in the vastus lateralis muscle were investigated in six male subjects (20-0 + 0.5 years, mean + S.E.M.) who performed one-legged cycling at 61 % of maximum 02 consumption (V02 max; determined with one leg) until fatigue or for a maximnum of 2 h.2. Analysis of pools of freeze-dried fibres obtained by needle biopsy and separated into specific types by the myofibrillar ATPase histochemical procedure indicated higher (P < 0 05) lactate concentrations in type II fibres compared to type I fibres at 15 min (43 9+9 7 and 512 +9 8 mmol (kg dry wt)-') and at 60 min (18-2+4-7 and 25-9 + 65 mmol (kg dry wt)-1). No differences existed in lactate concentration between fibre types for pre-exercise (10-0+ 1-6 and 13-3+2 8 mmol (kg dry wt)-') or post-exercise.3. Glycogen degradation was most pronounced in type I fibres. By the end of exercise, glycogen concentration was 82 4+45 mmol glucosyl units (kg dry wt)-' in type I fibres and 175 + 62 mmol glucosyl units (kg dry wt)-1 in type II fibres.4. No significant changes in ATP and creatine phosphate (CrP) were found in either fibre type with exercise.5. It is concluded that, at least for lactate and glycogen, fibre-specific differences are evident in prolonged submaximal exercise. The cause of the difference probably relates both to the unique energy metabolic characteristics of each fibre type and to the manner in which they are utilized during the exercise.