ABSTRACT (in the language of the thesis)
Purpose: To investigate the impact of concentric exercise-induced fatigue on proprioception, motor control,and performance of the upper-limb in handball athletes and non-athletes (healthy young adults). The second aim was to evaluate the impact of eccentric exercise-induced fatigue on proprioception, motor control, and upper-limb performance in handball athletes and compare its effects with concentric fatigue.
Μethods: Forty-six and thirty-three handball players were included to study the effects of concentric and eccentric exercise-induced fatigue respectively, on the outcome measures. In addition, twenty healthy active males were recruited as non-athlete control subjects. Proprioception was evaluated using joint reposition sense
(JRS), the threshold to detection of passive movement (TTDPM), motor control using the Y balance test upper quarter (YBT-UQ), and performance using the Athletic Shoulder test (ASH) before and immediately after fatigue intervention. Muscle onset latency (MOL) was assessed only after concentric exercise –induced fatigue. Fatigue protocol consisted of concentric or eccentric, maximal effort, and isokinetic contractions at 90˚/sec with sets of 30 repetitions (concentric) or 15 repetitions (eccentric) of the shoulder external and internal rotator muscles in the right arm. Fatigue was determined by a 60% 40% decline in the peak torque over three consecutive contractions despite reinforcing feedback and encouragement.
3 Results: After concentrically induced fatigue in handball players, a notable increase in absolute angular error (AAE) during joint repositioning, was found in all target angles in both external rotation (ER) and internal rotation (IR) directions (p < 0.01). In addition, a similar increase in TTDPM was found in internal rotation (p=0.020). Variable changes were found in YBT-UQ and ASH tests. Specifically, statistically significant differences were found in anteromedial (AM) (p=0.041), superolateral (SL) reach directions (p=0.005),composite score (p=0.009) in the right exercised hand and inferolateral (IL) reach direction in the left nonexercised hand (p=0.020) in the YBT-UQ. In addition, there was a significant reduction in isometric strength (ASH test) in the I position of the right hand (p=0.010) and all positions of the left hand (p<0.05). Furthermore, there was an increase of 47.37% in MOL scores after fatigue, but the increase was not significant (p > 0.05).Concentric fatigue in healthy non-handball players, induced a significant impairment in AAE at all target angles (p < 0.05). Moreover, there were no significant differences in kinesthesia (TTDPM), motor control
(YBT-UQ), and performance (ASH test) before and after fatigue intervention (p > 0.05). After eccentric fatigue in handball players, a notable rise (p < 0.05) in AAE was detected in five of the six target angles (ER15˚, ER30˚, ER45˚, IR15˚, and IR30˚). No statistically significant change in the target angle of IR45˚ (p= 0.967). Furthermore, there was a significant increase in TTDPM (p = 0.011). The YBT-UQ test revealed
statistically significant differences in all reach directions of the right hand. No statistically significant differences were found in the left hand (p > 0.05). The composite score (CS) shows a statistically significant difference only for the right hand (p < 0.001). Furthermore, after the eccentric fatigue, there was a decrease in the isometric strength in the ASH test for all hand positions on the right side and for two out of three test positions on the left side (p < 0.05). No significant change (p = 0.063) was found in the "T" Left-hand position.
Conclusions: Concentric exercise-induced fatigue of the rotator cuff muscles induces notable deficits in joint position awareness, kinesthesia, and motor control of the upper extremity in elite, male, handball players.
Although fatigue reduces reflex reaction time, the effect is only marginal. In addition, concentric exerciseinduced fatigue impaired proprioception but not motor control or performance in healthy non-athlete males.
Furthermore, eccentric exercise-induced fatigue of the rotator cuff muscles can cause significant impairments in joint position awareness, kinesthesia, and motor control of the upper extremities in elite male handball players.