Capacity of Electrical Activity and CK Isoenzymes (CKMM, CKMB) to Characterize Skeletal Muscle Injury

Abstract

PURPOSE: To determine the effects of fatiguing exercise on the spontaneous electrical activity and creatine kinase (CK) isoenzyme (CKMM, CKMB) levels in muscles during maximal relaxation measured immediately and 24 hours after exercise. METHODS: Ten male, high class competitive basketball players (23.6 ± 3.8 yrs), performed a graded exercise test (GXT) to exhaustion on a cycle ergometer (intensity increased 50W every 3 min). Before, immediately after and 24 h after the exercise bout, spontaneous electrical activity in the maximally relaxed muscles (m. rectus femoris) was measured by an electromyography (EMG) using concentric needle electrodes and 8 channel surface electrodes. EMG sensitivity: 30-100 mkV. At the same time CK activity in the capillary blood was determined using a biochemical analyzer. Statistical analyses were performed using repeated measures ANOVA. RESULTS: Total CK levels before exercise were 147±27 U/l, CKMM 127±47 U/l, and CKMB 22±8 U/l. Total CK and CKMM activity after exercise were higher (P < 0.05) 619±185 U/l, 493 ±133 U/l, respectively, and CKMB did not change significantly 24±17 U/l. Before the exercise bout spontaneous electrical activity in the maximally relaxed muscles was minimal. However, immediately after exercise the potentials were noticed significantly increased (P < 0.05) at 1.9 ± .3 ms length, 76.4±11.4 mkV amplitudes, 9.8±1.4 Hz frequency single-phase, dual-phase (2.6 ± .5 ms, 84.3 ±13.8 mkV, 5.4± .6 Hz), tri-phase (3.9 ± .6 ms, 98.4 ± 16.2 mkV, 3.8 ± 1.2 Hz). Long positive waves were registered in a few instances. After the exercise spontaneous electrical activity was noticed at 24 hours (14.9± 4.6 ms, 86.2 ±15.9 mkV, 2.4 ± .9 Hz). Noteworthy, in most instances this electrical activity was registered from the superficial layer of the muscle. CONCLUSIONS: There is significantly greater (P < 0.05) spontaneous electrical activity expressed immediately after exercise than pre-exercise, especially long positive waves and fasciculation, followed by increased CK isoenzymes activity (especially CKMM) in the fatigued muscles. This suggests muscular tissue damage. The signs of this damage are more expressed in the superficial layer of m. rectus femoris and this shows that fast twitch fibers are less resistant.