Injuries are a major adverse event during a soccer player’s career, as they require medical treatment and rehabilitation, thus interrupting a player’s activity for a period spanning from few weeks to several months. The most common of soccer injuries are sprains, strains and contusions occurring most frequently at the ankle, knee joints, and in the muscles of the thigh and calf . Between 8% and 33% of all injuries during the competitive phase are classified as overuse injuries .
Soccer matches and training are characterized by high-speed running while dribbling, passing, kicking or throwing the ball, with players required to make quick, precise movements, actions requiring multidirectional deceleration and acceleration . Thus, physical stress during training and/or match play prompts morphological, metabolic, and functional adaptations that consequently enable an increase in performance . On the other hand, the stresses of both training and competition result in temporary decrements in physical performance and not able levels of post-match fatigue which can be associated to increase of the risk of injury.
The magnitude of physical stress on the skeletal muscle system can be measured from the plasma creatine kinase (CK) and thermal images to determine changes in response to physiological processes or pathological reactions related to training and/or matches . Simultaneously, it is very important the use of an excellent recovery strategy that involves implementation of techniques or a combination of techniques in order to accelerate the time to achieve full recovery and potentially reduce the risk of injury.
In terms of recovery techniques, it is known that Intermittent Negative Pressure Therapy (INPT) is a vacuum-sealing technique that promotes negative pressure in the lower limbs, improving circulation and increasing capillarization and venous and lymphatic return. INPT is a completely painless therapy, regardless the type of injury or its stage, and can be used in wound treatment, which increases granulation tissue formation, removes edema, stimulates cell-mediated immune response, stimulates the central nervous system, decreases blood vessel permeability, and stimulates angiogenesis and blood flow to the wound margins .
In this sense, the aim of this study was to investigate the effects of INPT vs. Active Recovery Therapy (ART) in physiological parameters, such as thermal images of the lower limbs and serum CK level, in elite soccer players post-matches.
Subjects and anthropometric measurements
The study included 20 healthy male professional soccer players from a club in the Brazilian first division participating in national and international competitions organized by the Brazilian Soccer Confederation (CBF) and South American Soccer Confederation (CSF). Professional soccer players were randomly divided into two groups: Intermittent Negative Pressure Therapy (INPT; n=10; age: 20.4 ± 3.7 years; height: 178.5 ± 6.2cm; weight: 74.3kg ± 5.2 kg; % body fat: 10.4 ± 4.1 %) and Active Recovery Therapy (ART; n=10; age: 21.7 ± 4.3years; height: 179.5 ± 5.2cm; weight: 73.8kg ± 6.2 kg; % body fat: 10.8 ± 4.6 %). The players’ training frequency was 6.1 ± 0.5 days/week with training programs consisting of jumps, contesting possession, sprints, accelerations, and decelerations. All soccer players included in the study participated in 2 official matches for 87.4 ± 9.3 minutes. All official matches were interspersed by 4 days.
Intermittent Negative Pressure Therapy (INPT)
The subjects were comfortably clothed and seated for 15 minutes before the experiment started and then all subjects of the INPT group were conducted to vacuum chamber with internal padding to allow insertion of both leg which suck air out in the bag and create a hypobaric environment in the bag (Vacusport® ; Weyergans High Care, Dueren, Germany). All measurements occurred in a quiet and temperature-controlled environment (temperature 21ºC, 65% relative humidity) to allow patients to obtain their thermoneutral zone and to reduce sympathetic stress that could create artifact.
Active Recovery Therapy (ART)
Subjects of the ART group realized a protocol of active recovery for 30 minutes 24 hours post-match. ART was divided into three moments: (1) a foam roller (FR) with dimensions of 6.25″ x 6.25″ x 20.25″ (SKLZ, CA, USA) was applied over antero-posterior regions of the thighs and legs. in both lower limbs for 4 sets of 20 s in each regions of interest with 20s of rest between each set. The subjects started at the proximal region of the thighs and legs and rolled down toward to distal region. All subjects were instructed to utilize their body mass over the thighs and legs with the help of the arms to make the movement and speed was controlled by a metronome (2s per pass); (2) all participants were conducted a 10-min mobility and stability exercise regime comprising multiple sets (i.e., 2–3 sets) from static movements to dynamic movements and finally combination of these. Exercise program involved muscular activation of lower limbs and trunk muscles using five exercises for antero-posterior regions (i.e., prone planks; shoulder bridges; single leg dead lift with body weight; side brides; and sidestep with elastic resistance around the thighs in a squatted position) with 10–15 s contraction time (isometric condition) and 8–10 repetitions (dynamic condition); (3) and lastly it was carried out an active recovery using a cycle ergometer (60 rpm, 80 W) for 10 minutes. The ART protocol was supervised by a physical trainer with more than 10 years of experience.
Plasma CK Monitoring Proceedings
Plasma CK monitoring was assessed by reflectance photometry at 37°C using the Reflotron Analyser Plus (Reflotron Plus; Roche, Germany) which was previously calibrated following manufacturer’s instructions. After sterilizing the finger using 70% ethyl alcohol, a lancet with an automatic trigger was used to puncture the tip finger and blood was drained into heparinized capillary strips for analysis. A 32 µl sample of blood was immediately pipetted into a CK test strip and inserted into the analyzer. All measurements were performed 24h post-match, 24h immediately post-recovery therapy (INPT or ART) and 48h post-match between 8:00 and 9:00 A.M . within an acclimatized room (temperature 21ºC, 65% relative humidity). Absolute values of CK were used for analysis.
Acquisition of Thermal Images
With temperature of 21ºC with a relative humidity of 65%. Thermal images sequences of lower limbs (thighs and legs) were acquired in an antero-posterior manner (i.e., frontal and dorsal views) by a digital infrared thermal camera (Flir Systems Inc®, model T-540, POLISCAN Brasil) with a measurement range of 20°C to 1500°C (accuracy of ± 2°C or 2 %; sensitivity of ≤ 0.05°C). Selection of the ROI utilized 5 cm above the upper border of the patella and groin line for the thigh, and for the leg, 5 cm below the lower border of the patella and 10 cm above the malleolus . In relation to knee, thermographic images were taken on one image around the patella.
All data were presented as mean ± SD. Statistical analysis was initially performed using the Shapiro–Wilk normality test and the homoscedasticity test (Bartlett criterion). A Student’s t-test was used to assess differences in the indicators of external load between matches (match #1 vs. match #2). Comparisons between 24h post-match, 24h immediately post-recovery therapy and 48h post-match for INPT vs. ART were performed by factorial ANOVA 3 x 2 with Bonferroni post-hoc tests. The level of significance for all statistical comparisons was set at p<0.05.
Serum CK level revealed significant decrease (p=0.01) in the period of 24h immediately post-recovery therapy (∆= 401.2 U/L-1) and 48h post-match (∆= 296.4 U/L-1) in INPT when compared to ART.
No showed significant difference 24h post-match between INPT vs. ART for maximal and mean skin temperatures values in the thigh and leg in anterior and posterior views with temperature range values about 32.3 – 33.1 ºC and 31.5 – 32.4 ºC, respectively. On the other hand, significant decrease was found between from both anterior and posterior measurements of thighs and legs for maximal and mean thermal images in INPT when compared to ART during period of 24h immediately post-recovery therapy (p=0.001) and 48h post-match (p=0.01). Significant decrease in maximal and mean thermal images values of knee during period of 24h immediately post-recovery therapy and 48h post-match (p=0.01) with INPT. No significance difference (p>0.05) was found between left and right sides from both anterior and posterior measurements of thighs and legs for maximal and mean skin temperature.
It was observed contralateral thermal symmetry in the lower limbs (ROI < 0.2°C). Serum CK level and thermal images of lower limbs shown better recovery up to 48h post-match with the use INPT in elite soccer players. Thus, major benefits embracing INPT and physiological evaluations may be more helpful for athletes, coaches, physicians and physical therapists regarding injury prevention, early detection and recovery strategies. Therefore, coaches should consider these data when planning workouts and trainings after matches and also for closely monitoring athlete´s recovery in order to determine readiness for activity. While data from other sports would be needed to identify similar post-competition trends, it is suspected that active recovery held the day after a game may be counterproductive and impeded the recovery process, which may take more than 48 hours.
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