What is cryotherapy?

Cold water cooling of the lower extremities is a form of regeneration after athletic exertion. Increasingly, this method is used by elite athletes to minimize muscle pain and accelerate recovery after exercise. Accelerated short-term recovery (hours to days) can improve competitive performance, allow for higher training loads, or enhance the effect of a previous training load. In this context, cryotherapy lives up to its name once the water reaches temperatures below 15 degrees Celsius.

Active or passive regeneration?

Against this background, a pilot study was designed and conducted in collaboration with the Olympic Training Center Freiburg-Schwarzwald to provide an approximation of the correct cooling process and to answer the question of whether there is a difference between cold water cooling by icebein and "active" regeneration. The dependent variables subjective muscle pain, recovery, and athletic performance were examined. Participants randomly assigned to two groups according to inclusion and exclusion criteria are athletically active men aged 19-26 years with no mental or health limitations. The two intervention groups are assigned to an icebein and an "active" recovery group in a cross-over design, so that each participant undergoes each condition and thus could also compare both types of recovery.

Importance of regeneration

Sporting activity is characterized by factors of the type, duration and intensity of the load. Depending on the extent of these factors and the associated recovery time, damage to the muscles, inflammation and fatigue in the nervous system occur, as well as energy substrate depletion. Particularly in competitive sports, close training and competition cycles result in increased physical stress, which has a negative effect on muscle function and sensation and consequently on performance. Therefore, rapid recovery has become all the more significant. According to Bleakley et al. 2012 meta-analysis, cold water cooling is the most commonly used recovery method after athletic activity to delay Delayed Onset Muscle Soreness (DOMS).

Delayed Onset Muscle Soreness (DOMS)

DOMS are microscopic tears in muscle tissue called exercise-induced muscle damage that can lead to delayed onset muscle soreness. DOMS typically peak between 24 and 48 hours-sometimes up to 72 hours-after exercise and are characterized by muscle shortening, increased passive stiffness, swelling, decrease in strength and power, localized muscle soreness, and altered proprioception.

How does cryotherapy work?

The physiological background of cryotherapy is based on the dissipation of body heat by reducing tissue temperature. This is manifested in a reduced muscle pain perception, so that the body feels more "awake" after exercise and causes a lower feeling of fatigue. In addition, due to the cold, the body lowers heart rate and cardiac output, inducing vasoconstriction. Results include smaller vessel diameters, a reduced incidence of edema, and improved oxygen delivery to cells. In addition, to maintain the core temperature of the body, the central metabolism increases, favoring the transport of waste products. All of these effects in composition could reduce exercise-induced inflammation by mitigating hypoxic cell death or damage and minimizing secondary tissue damage by reducing leukocyte and monocyte infiltration.

The first minutes of contact with the cold water cause skin cooling followed by neuromuscular cooling. After approximately 20 minutes of cold water contact, we refer to long-term immersion and deep tissue cooling. However, deep tissue cooling is counterproductive for athletic activity because it contributes to nerve blockage and thus muscle dysfunction and peripheral paralysis. This means that extremes of below 10 degrees water temperature contribute to contraindications and (may) reduce recovery and therefore, conversely, performance.

The pilot study

Some studies have already proven that, provided that cold water cooling is carried out correctly, immersion in cold water is a way to regenerate more quickly. It has already been observed that only after ten minutes in cold water, a change in the blood occurs. Therefore, also in the pilot study in Freiburg, numerous factors such as duration of cooling (at least ten minutes), water temperature, type and intensity of training, as well as the time between training and recovery sessions were taken into account and scientifically investigated. This was done by objective criteria and subjective questionnaires. Against the background that there is no generally valid concept for optimal regeneration, a setting was created with regard to duration, temperature and interval between exercise and regeneration that promised the greatest possible success based on the current state of research. The design called for icebein or alternatively "active" regeneration to be performed immediately after a cycling sprint protocol. According to previous research, it should be performed as soon as possible (0-3 hours) after exercise in order to have an effect on physiological processes.

Participants in the icebein group sat in the cooling legs at a temperature of 10 degrees Celsius for 15 minutes. Since the body produces and expels more heat after exertion, the temperature had to be adjusted downward by two degrees Celsius after a trial run (8 degrees Celsius) to allow constant cooling at ten degrees Celsius throughout the 15 minutes. "Active" regeneration took place following the protocol of Lane and Wenger (2004). Here, body weight was used to determine the resistance to be overcome (in watts), which then required cycling between 65 and 85 revolutions per minute. Participants were able to track and correct their performance on the bike at all times via a monitor.  

All participants had to complete identical cycling programs after a standardized warm-up program and repeat this after 24 hours. The general conditions for the recovery phases icebein (clothing, duration, water temperature) and active regeneration (duration, resistance) were also predetermined. After a one-week "washout phase" (to avoid overhang effects), the cycling program was repeated, but the type of regeneration was changed. With the help of accompanying questionnaires, various data concerning muscle condition, body sensation and sleep were collected.

Conclusion

In this pilot study, the effect of icebein and "active" recovery on musculoskeletal pain, subjective recovery, and total work (in Kj) after a high-intensity bike sprint protocol was investigated. A significant increase in musculoskeletal pain was observed, as early as one hour after the cycling sprint protocol. 

Cold water intervention through icebein application stimulates cold receptors and causes vasoconstriction of peripheral blood vessels, diverting blood to the warmer core. It is believed to reduce muscle blood flow and muscle metabolism, which helps reduce inflammatory responses such as edema or lysosomal activity. The peak of muscle pain is already reached one hour after the cycling sprint protocol and decreases continuously over the following 24, 48 and 72 hours. In contrast, the "active" recovery showed the typical picture of delayed muscle soreness. The peak of muscle soreness is reached only 24 hours after the wheel sprint protocol and remains at similar levels up to 48 hours afterwards. Consequently, the icebein intervention facilitated the recovery process.

In addition, all subjects preferred the icebein cryotherapeutic application to normal active recovery. Likewise, it could be shown that the cold distribution on the pants was evenly distributed everywhere and exactly at the level of the indicated temperature.    

The whole icebein Recovery Family would like to thank the Olympia Stützpunkt Freiburg and especially Mrs. Raphaela Lamprecht for the good cooperation.

Note on completeness:
Due to the small sample size and methodological limitations, this data set cannot yet provide causal or definitive statements about the difference between the two types of regeneration. Rather, this study serves to gain knowledge and determine effect sizes in order to provide the basis for a more extensive research project.