Post-viral fatigue syndrome. A longitudinal assessment in varsity athletes.

Maximal oxygen uptake, anaerobic threshold (AT), isometric strength of the elbow flexor and knee extensor muscles, isometric strength endurance exhaustion time (prolonged contraction at 66% of maximal isometric strength), uphill sprinting exhaustion time were longitudinally studied in eight varsity endurance runners with post-viral fatigue syndrome (PVFS). Prolonged impairment of exercise performance is evident during the course of PVFS. Although maximal oxygen uptake (VO2max) had returned to pre-infection values 13 months after the viral illness (4.160 vs 4.0 L.min-1), AT was still significantly reduced [52 ml.kg-1.min-1, 18.6 km.hr-1, 176 bpm, and 82% of VO2max vs. 49.1 ml.kg-1.min-1 (p < 0.05), 175 bpm (NS), 17.2 km.hr-1 (p < 0.01) and 79% of VO2max (NS)]. Maximal isometric contraction strength of the upper limb remained constant (282 N vs. 274 N), while knee extensor muscles strength decreased significantly (730 N vs. 701 N, p < 0.05). Strength endurance was still significantly reduced by the end of the study (arm average pre-infection: 46.2 sec; end of study: 29.3 sec, p < 0.001; leg average pre-infection: 66.4 sec; end of study: 49.1 sec, p < 0.01). Up hill sprinting time was similarly reduced by the end of the study period (29.3 sec vs. 16.2 sec, p < 0.01). Both aerobic and anaerobic exercise variables are seriously affected by post-viral fatigue syndrome, and one year may not be sufficient to fully recover.