Recovery kinetics of knee flexor and extensor strength after a football match

© 2015 The Authors. Published by PLOS. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1371/journal.pone.0128072We examined the temporal changes of isokinetic strength performance of knee flexor (KF) and extensor (KE) strength after a football match. Players were randomly assigned to a control (N = 14, participated only in measurements and practices) or an experimental group (N = 20, participated also in a football match). Participants trained daily during the two days after the match. Match and training overload was monitored with GPS devices. Venous blood was sampled and muscle damage was assessed pre-match, post-match and at 12h, 36h and 60h post-match. Isometric strength as well as eccentric and concentric peak torque of knee flexors and extensors in both limbs (dominant and non-dominant) were measured on an isokinetic dynamometer at baseline and at 12h, 36h and 60h after the match. Functional (KFecc/KEcon) and conventional (KFcon/KEcon) ratios were then calculated. Only eccentric peak torque of knee flexors declined at 60h after the match in the control group. In the experimental group: a) isometric strength of knee extensors and knee flexors declined (P<0.05) at 12h (both limbs) and 36h (dominant limb only), b) eccentric and concentric peak torque of knee extensors and flexors declined (P<0.05) in both limbs for 36h at 60°/s and for 60h at 180°/s with eccentric peak torque of knee flexors demonstrating a greater (P<0.05) reduction than concentric peak torque, c) strength deterioration was greater (P<0.05) at 180°/s and in dominant limb, d) the functional ratio was more sensitive to match-induced fatigue demonstrating a more prolonged decline. Discriminant and regression analysis revealed that strength deterioration and recovery may be related to the amount of eccentric actions performed during the match and athletes' football-specific conditioning. Our data suggest that recovery kinetics of knee flexor and extensor strength after a football match demonstrate strength, limb and velocity specificity and may depend on match physical overload and players' physical conditioning level.Published versio

Effective ways of restoring muscular imbalances of the rotator cuff muscle group: a comparative study of various training methods

Background: Many studies have compared different training methods for improving muscular performance, but more investigations need to be directed to the restoration of muscular imbalances. Objective: To determine the most effective training for altering strength ratios in the shoulder rotator cuff. Methods: Forty eight physical education students were randomly assigned to four groups (12 per group): (a) experimental group who carried out multijoint dynamic resistance training for shoulder internal and external rotation movement (pull ups or lat pull downs, overhead press, reverse pull ups, push ups) (MJDR group); (b) experimental group who exercised the same muscle group using dumbbells weighing 2 kg (isolated group); (c) experimental group who followed an isokinetic strengthening programme for the rotator cuff muscle group (isokinetic group); (d) control group who had no strength training. Testing was performed in the supine position with the glenohumeral joint in 90° of abduction in the coronal plane, with a range of motion of 0–90° of external rotation and 0–65° of internal rotation at angular velocities of 60, 120, and 180°/s. The test procedure was performed before and after the exercise period of six weeks. Results: One way analysis of variance found no differences between the groups for the initial tests. Analysis of variance with repeated measures showed that the strength ratios in all the experimental groups had altered after the exercise period, with the isokinetic group showing the most significant improvement. Conclusions: Isokinetic strengthening is the most effective method of altering strength ratios of the rotator cuff muscle