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The Effect of Post-Exercise Cryotherapy on Recovery Characteristics: A Systematic Review and Meta-Analysis.
PLoS One. 2015 Sep
The aim of this review and meta-analysis was to critically determine the possible effects of different cooling applications, compared to non-cooling, passive post-exercise strategies, on recovery characteristics after various, exhaustive exercise protocols up to 96 hours (hrs).
A total of n = 36 articles were processed in this study. To establish the research question, the PICO-model, according to the PRISMA guidelines was used. The Cochrane’s risk of bias tool, demonstrated a high risk of performance bias and detection bias.
Research Question and Search Algorithm
The research question was defined by the PICO-model (PRISMA): Population: healthy, non-injured, female and male study participants, participants could be of any training status; Intervention: external applications, only post-exercise cryotherapy accepted; Comparator: passive control interventions without cooling, passive sham / placebo applications; Outcomes: DOMS and RPE, levels of venous or capillary blood plasma markers (CK-lev- els and blood/muscle lactate-levels respectively lactate dehydrogenase [LDH]-levels) and/or blood plasma cytokines (IL-6, CRP), measured 24 hrs, 48 hrs, 72 hrs and/or 96 hrs after exhaustive exercise. DOMS and RPE were defined as subjective recovery characteristics in this study. The subjective perception of DOMS was rated on various scaling systems, such as visual analogue scales (VAS), BORG scales or Likert-scales. RPE was rated by various scaling systems, such as BORG scales or VAS. CK-levels, lactate-levels, CRP and IL-6 were defined as objective recovery characteristics in this study. The rationale for inclusion of these outcome variables was comparability.
Literature Search Strategies and Data Sources
A systematic search was accomplished between Oct 2013 and Aug 2014 according to the PRISMA. The following key words and their combinations were used without using any automatic filters: “Exercise AND Cold OR Cooling OR Cryotherapy AND Recovery OR Recov- ery Strategy OR Recovery Modality”. Seven additional articles were included after having read the reference list of the eligible studies (n = 49).
Study Selection Criteria
Inclusion criteria for the articles were:
- (1) the study design was randomized or quasi randomized into an intervention group and a non-cooling, passive control group;
- (2) the cold therapy had to be an external application form without combinations, focused on the mentioned outcome variables after the exercise bouts;
- (3) the cold interventions had to be compared to at least one control condition;
- (4) the outcome variables had to be measured immediately (0–24 hrs), and / or 24 hrs, and / or 48 hrs, and / or 72 hrs and/or 96 hrs post-exercise;
- (5) the data of the outcome variables had to be processed in the articles;
- (6) the human volunteers had to be healthy without any physical infirmity;
- (7) the human volunteers could be of any athletic training status;
- (8) there were no sex-defined inclusion or exclusion criteria;
- (9) at least one of the subjective or objective recovery characteristics had to be evaluated in the articles;
- (10) the cold therapy had to be applied within one hour after the end of the exercise protocol;
- (11) all exhaustive exercise types or muscle damaging protocols were accepted;
- (12) English and German language restrictions.
Articles, which did not meet these criteria were excluded from this study according to the flowchart.
Study and Population Characteristics
A total of n = 36 articles met the inclusion criteria. The total study population of all selected articles comprised 574 healthy volunteers (412 male and 72 female).
Characteristics of the Cooling Applications
The most common cold therapy application (28 studies) was CWI of the legs. The water temperature in the leg immersing studies was 5°C to 10°C in 15 articles and 11°C to 15°C in 13 articles. The participant where often immersed until the iliac crest or umbilicus.
Characteristics of the Passive Control Interventions
The predominant passive control condition, used in 30 studies, was sitting, standing or resting supine in a room with comfortable temperatures, ranging from 15°C to 24°C.
From the current results, one can conclude, that cooling is superior compared to passive recovery strategies after various exhaustive or muscle damaging exercise protocols.
These results relate to the subjective effects of different cooling applications. Cooling showed significant effects in reducing the symptoms of DOMS (up to 96 hrs) and RPE (up to 24 hrs) compared to passive control interventions. CWI achieved the best effect with respect to the other cooling applications.
To sum up the results of the individual studies: the mean temperature of the studies, showing a significant result favouring cooling compared to the passive recovery interven tion, was 10°C (range: 5°C to 13°C). The reported and suggested cooling time for alleviating the subjective symptoms is 13 min (range: 10 min to 24 min). Cooling did not significantly affect the objective recovery outcomes compared to passive control interventions.