the aim of this study was to investigate the changes in the concentrations of plasma ammonia and lactate to an anaerobic exercise response, lasting 90 seconds (s) in duration. the secondary purpose was to plot this relationship versus muscle fibre type. four muscle biopsy sample (7 mg each) were taken from each subject (n = 25). all muscle samples were stained using the myosin atpase ph 10.0> 4.30 and 4.58 technique. this allowed for differentiation of the st, fta and ftb muscle fibres. two weeks post surgery blood was sampled from an indwelling catheter in the antecubital vein before, immediately after, and four minutes after 90s of exercise. plasma blood was assayed for both ammonia and lactate. a one way analysis of variance (anova) with repeated measures was performed for each metabolite followed by a tukey hsd post-hoc test. correlations were calculated for exercise, blood, and muscle variables. muscle fibre profiles percentages were as follows st - 53.48 (±8.82), ft - 46.52 (±8.82), ftb (percentage of ft population) - 8.73 (±4.63). the peak power was 6.54 w/kg (±0.83) and the relative capacity was 687.3 j/kg (±86.3). the capacity score was higher than scores reported previously for the similar protocol. mean plasma ammonia values were 66.65 (±33.45), 130.0 (±37.15), and 251.8 (±61.82) mol/1 at rest, immediately post-exercise and at 4 minutes post-exercise respectively. the increase in ammonia concentration over time was significant (p < 0.01). mean plasma lactate values were 1,45 (±.52), 8.30 (±3.11), and 14.08 (±2.62) mmol/1 at rest, immediately post-exercise and 4 minutes post-exercise respectively. lactate increase over time was significant. there was a significant positive relation between plasma ammonia and lactate over time (r = .77, p < 0.05). regression analysis of percentage ft muscle fibre and ammonia increase demonstrated a correlation of r = .58 (p < 0.05, one tailed) amongst those individuals with a 40 percent or greater ft profile. it appears that in this study plasma ammonia values were higher at 4 min. post exercise than at immediately post exercise. ammonia and lactate rise linearly with exercise and have been demonstrated to be related over time. a relation between ammonia and ft muscle fibre existed in this examination; the greater the percentage ft fibres the higher the ammonia concentration in blood plasma.