Introduction
In the days following unaccustomed or intense training or competition, athletes often experience dull, aching pain, stiffness, and loss of muscle strength that can last for up to 5-7 days. This phenomenon is termed exercise-induced muscle damage (EIMD). Muscle damage is characterized by a sustained reduction in optimal force production, the delayed onset of muscle soreness (DOMS), and an acute inflammatory response. It has been proposed that cold therapies aid recovery following EIMD through a dampening of the inflammatory response, edema reduction, and through an analgesic effect.
A novel form of cold therapy, Whole Body Cryotherapy (WBC) has gained popularity in athletes as an anti-inflammatory treatment. A typical session of WBC involves standing in a chamber that fills with a safe, but extremely cold gas, maintained at temperatures of -110 degrees Celsius to -190 degrees Celsius (-166 to -220 degrees Fahrenheit) for at least two minutes and a maximum of five minutes. The authors in the study, Whole-body Cryotherapy as a Recovery Technique after Exercise: A Review of the Literature, present an overview of the current research on the topic and provide recommendations for its use by athletes.
Discussion
Four key outcome measures for EIMD utilized in this review include pain, muscle function and performance, inflammatory marker levels, and creatine kinase (CK) levels as a marker of muscle damage.
Pain
The visual analog scale was utilized in the five articles that used pain as an outcome measure. Four studies found a significant decrease in pain by at least 18% when compared to a control at 48 hours post WBC treatment. In one study, there was also decreased pain compared to the control group when performing a body weight squat post-WBC treatment, suggesting WBC treatment may reduce pain during subsequent muscle contractions.
Muscle Function and Performance
Patients received an average of 15 WBC treatment exposures across the six studies that measured muscle function. In one study, a group of tennis players were exposed to WBC every day over a five-day training program. In this study, the WBC group reached fatigue significantly later during a progressively more difficult tennis drill than a control group. The WBC group also experienced a 7.3% increase in stroke effectiveness during a tennis skill game that became progressively more difficult where the control group only increased by 2.6%. In another study, synchronized swimmers were exposed to WBC each day during a period of intensified training and found that a 400 m time trial swim speed was only 0.5% slower after WBC compared to a 1.1% time reduction in the group that did not receive WBC treatment.
Inflammation
The authors who focused on inflammatory marker levels used concentrations of interleukins, tumor necrosis factor (TNF), and C-reactive protein (CRP) to show the amount of inflammation present in the muscle. One study looked at the inflammatory response in runners following a 48-minute simulated trail run. Concentrations of the acute inflammatory marker, CRP, were increased by 515% from baseline in the control group and 123% in a WBC group. The increase of inflammatory interleukin cells that naturally occurs after damaging exercise was limited when participants were exposed to WBC compared to the control.
In another study which observed the effects of WBC prior to exercise, the concentration of the pro-inflammatory interleukin increased more than six times in the control group compared to athletes who were treated with WBC. In addition, interleukin concentration dropped by 11%, indicating that treatment blunted the inflammatory response and possibly reduced muscle damage. Yet another study found WBC increased the concentration of an anti-inflammatory cytokine to twice that of baseline compared to no change relative to baseline in the control group. Further, the interleukin concentrations dropped by 80 % in the WBC group compared to a drop of only 50% in the control subjects . The final study found that a five-day training protocol combined with WBC induced a 60% decrease in the inflammatory cell, TNF-α.
Muscle Damage
Muscle damage focused studies used a measure of CK to determine the amount of breakdown in muscles. One study showed a 30% decline in CK after ten exposures to WBC over a five-day period as compared to a control group. A second study reported that CK concentrations were 34% lower with the inclusion of WBC treatment six days into a training protocol compared to a training protocol without WBC treatment. These results were supported by a separate study that reported daily exposure to WBC over a five-day training program with elite rugby players reduced CK by 40%. Another study found WBC treatment significantly reduced CK in tennis players where concentrations of this muscle enzyme in the control group remained virtually the same after five days of training. A final study found no significant changes in CK relative to a control group with protocols using either three or six exposures to WBC. The results from this study suggest that there may be a dose response to WBC when assessing CK concentration, where a reduction in circulating CK is in proportion to the number of exposures to WBC during the recovery process.
Limitations and Future Research
The lack of ability to blind for recovery treatment in the research makes it impossible to eliminate the potential placebo effect. Further investigation into the effects of multiple WBC exposures during extended periods of athletic training is warranted to determine potential effects on recovery, performance and processes of muscle adaptation. Future studies will require larger sample sizes to determine the significance of immunological changes and stringent methodological control to identify the exact influence of WBC on these pathways.
Conclusion
In conclusion, the studies referenced in this article suggest that WBC may be successful in decreasing pain, inflammation, and muscle damage and increasing muscle function. With WBC treatment groups recording pain scores an average of 31% lower than control groups, evidence tends to favor WBC as an analgesic treatment after damaging exercise. Data from inflammatory markers and CK suggest that WBC may dampen the inflammatory cytokine response which means less tissue damage and a faster recovery. Multiple exposures of three or more sessions of three minutes conducted immediately after and in the two to three days post-exercise have presented the most consistent results. There are contraindications to this modality including hypertension, circulatory disorder, and history of a stroke, to name a few. The athlete or patient needs to be properly screened and perform a thorough healthy history prior to treatment.
PT First Implications
As the research on WBC continues to evolve, this treatment could be a good adjunct to skilled physical therapy during an athlete’s training. Localized cryotherapy is a common modality seen in a physical therapy setting to treat pain and inflammation. WBC provides an avenue to treat more widespread muscle pain in multiple area of the body and could be beneficial for athletes during their training season.
Reference:
Rose, C., Edwards, K., Siegler, J., Graham, K., Caillaud, C (2017). Whole-body Cryotherapy as a Recovery Technique after Exercise: A Review of the Literature. International Journal of Sports Medicine. 38: 1049-1060.