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

Time of sampling is crucial for measurement of cell-free plasma DNA following acute aseptic inflammation induced by exercise

Objectives: To determine the time-course changes of cell-free plasma DNA (cfDNA) following heavy exercise. Methods: cfDNA concentration, C-reactive protein levels (hs-CRP), uric acid concentration (UA), creatine kinase activity (CK) were measured before and post-exercise (immediately post, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 8 h, 10 h, 24 h). Results: cfDNA increased (15-fold) 30-min post-exercise and normalized thereafter. hs-CRP increased (56%, p&lt;0.001) 1 h post-exercise, remained elevated throughout recovery (52-142%, p&lt;0.0001), and peaked (200% rise, p&lt;0.0001) at 24 h post-exercise. UA and CK increased (p&lt;0.05), immediately post-exercise, remained elevated throughout recovery (p&lt;0.0001), and peaked (p&lt;0.0001) at 24 h of post-exercise recovery. Conclusions: cfDNA sampling timing is crucial and a potential source of error following aseptic inflammation. (C) 2010 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved

The contents and duration of daily training sessions performed during the post-match period.

<p>The contents and duration of daily training sessions performed during the post-match period.</p

Changes of functional ratio in response to a football match.

<p>KF_ecc/KE_con, functional ratio; h, hours; ¹Significant difference with baseline; ²significant difference between groups; ³significant difference between dominant and non-dominant limb at corresponding time; ⁴greater decline in functional ration compared to conventional ratio at corresponding time;⁵greater decline at 180°/s compared to that at 60°/s at corresponding time.</p

Participants’ characteristics.

<p>BMI, body mass index; VO_2max, maximal oxygen consumption; HR, heart rate; HRmax, maximal heart rate; Yo-Yo IR2, Yo-Yo intermittent recovery test-level 2; ¹recorded during the graded exercise test used for the assessment of VO_2max.</p><p>Participants’ characteristics.</p

Changes of soreness (A-B), CK activity (C) and leukocyte counts (D) following a football match.

<p>MS, muscle soreness; CK, creatine kinase activity; h, hours; C, control group; EG, experimental group; KE-C, knee extensors of control group; KE-EG, knee extensors of experimental group; KF-C, knee flexors of control group; KF-EG, knee flexors of experimental group; ¹Significant difference with baseline; ²significant difference between groups; ³significant difference between dominant and non-dominant limb at corresponding time; ⁴greater decline in functional ration compared to conventional ratio at corresponding time;⁵greater decline at 180°/s compared to that at 60°/s at corresponding time.</p

Discrimination of players of the experimental group into a high- and low-performer subgroup based on physical activity variables indicative of match's external load as derived from cluster and discriminant analysis.

<p>¹ Within-groups correlations between discriminating variables and standardized canonical discriminant functions.</p><p>Discrimination of players of the experimental group into a high- and low-performer subgroup based on physical activity variables indicative of match's external load as derived from cluster and discriminant analysis.</p

The physiological profile of the football match.

<p>¹Significant difference with baseline</p><p>²significant difference between groups</p><p>N/A, not applicable.</p><p>The physiological profile of the football match.</p