Sports Medicine Research: In the Lab & In the Field: Are Current Cryotherapy Protocols Sufficient to Reduce Microvascular Blood Flow? (Sports Med Res)


Monday, November 28, 2011

Are Current Cryotherapy Protocols Sufficient to Reduce Microvascular Blood Flow?

Microvascular Perfusion and Intramuscular Temperature of the Calf During Cooling

Selkow NMDay CLiu ZHart JMHertel JSaliba SA. Med Sci Sports Exerc. 2011 Oct 7. [Epub ahead of print].

Cryotherapy has been proposed to decrease local blood flow through vasoconstriction, decrease metabolic activity, reduce cellular oxygen requirements, and decrease local tissue temperature; however, the optimal physiological responses (e.g. how much should blood flow, cellular metabolism, and tissue temperature be decreased, if at all) are still unknown.  The purpose of this single-blind crossover study was to examine microvascular perfusion changes in the gastrocnemius after a cryotherapy intervention. Nineteen healthy subjects (age = 18 to 30 years) completed 2 sessions (crushed ice bag and sham) in a random order.  The treatment time of cryotherapy or sham was tailored to each patient based on the thickness of adipose tissue overlying the gastrocnemius (treatment time: 10 to 60 minutes).  Outcome variables of microvascular perfusion (blood flow and blood volume) and intramuscular temperature were measured at baseline (pre-treatment) and immediately following crushed ice bag or sham.  All measurements were performed 1 cm in to the muscle.  Contrast enhanced ultrasound, which was used to measure microvascular perfusion, is also used in cardiac patients to determine blood flow to the heart.  The results of this study show that compared to baseline measurements, microvascular blood flow and blood volume were not different immediately after ice bag treatment, but were increased after sham treatment.  Intramuscular temperature decreased significantly during ice bag treatment, but did not change during sham treatment.  Additionally, subcutaneous adipose tissue thickness at the treatment site was significantly correlated with change in intramuscular temperature immediately after cryotherapy treatment.    

This is the first study in humans to suggest that microvascular blood flow and blood volume may not decrease during cryotherapy treatment, even though muscle temperature decreased significantly.  It is commonly thought that lower tissue temperature will result in decreases in blood flow, but this study questions that theory.  The sham group had an increase in microvascular perfusion immediately after treatment that may have been due to micro-trauma from insertion of the small temperature probe into the muscle.  This suggests that ice bag application controlled the microvascular perfusion associated with the micro-trauma of probe insertion, indicating that cryotherapy treatment may have a protective function.  This provides further support for the use of cryotherapy as quickly as possible after injury to control perfusion and potentially limit further injury, though more research needs to be completed to confirm this theory.  This study also confirms a relationship between subcutaneous adipose tissue thickness and amount of time required for cooling, but this relationship implies that the currently recommended treatment times to achieve a meaningful change in tissue temperature based on adipose tissue thickness may not be correct.  Clinicians and researchers should think critically about the timeframe after injury, patient’s body composition, and treatment goals before prescribing a cryotherapy treatment.  We should also begin to consider different mechanisms in which cryotherapy may be acting to create a successful treatment, such as changes in cutaneous sensation, counter-irritation, or noxious inhibition.  Do the results of this study change the way you view cryotherapy treatments after acute injury?  Do you believe that cryotherapy treatments should be tailored to individuals based on their body composition or injury?   

Written by: Kimberly Rupp
Reviewed by: Jeffrey Driban

Related Post:

Selkow NM, Day C, Liu Z, Hart JM, Hertel J, & Saliba SA (2011). Microvascular Perfusion and Intramuscular Temperature of the Calf During Cooling. Medicine and Science in Sports and Exercise PMID: 21988932


Meghan Melinchak, ATC said...

A really important aspect this research study brought up was the imporance of tailoring the treatment to the patient. I know, more often than not, twenty minutes is the run of the mill answer to "how long should I ice for?" regardless of if you're dealing with a 350 lb lineman or itty bitty gymnast. That being said, its not practical to measure the subcutaneous fat and muscle thickness of each and every athelte that we want to ice. Some standard or guidelines need to be set that does this.

Kimberly Rupp said...

Thanks, Meghan. I agree that it isn't usually practical to measure subcutaneous tissue in a clinical setting, but I do think it's safe to get to know your athletes' and patients' body types and estimate the thickness of subcutaneous tissue. Recently, studies have tried to make recommendations on cooling time based on body composition, but this study highlights the fact that those recommendations may be too short to achieve the physiological effects we desire. Hopefully in the near future we will have a new set of recommendations for cryotherapy treatment length in different body types. Thanks for your comment!

Mark Feger said...

I agree with both of your comments and the study has very interesting findings. However, I think when deciding whether or not to continue cryotherapy application on acute conditions other treatment goals and mechanisms of cryotherapy must be considered. What are your thoughts on the ability of cryotherapy to decrease cellular metabolism and thus decreasing the need for oxygen following injury? If volume of blood to the tissue itself does not change but the amount oxygen delivered relative to the demand is increased do you still think the reduction in a hypoxic state is a beneficial outcome of cryotherapy in an acute stage?

Kimberly Rupp said...

Mark - great comment. I think the theme of this article was that ice may still be beneficial after acute injury, even though blood flow did not decrease below baseline levels. The protective effect was mentioned because the sham group had increased blood flow; this suggests that ice exerted some effect on blood flow, it just wasn't as dramatic as we assume. Decreases in cellular metabolism and oxygen demand to counteract hypoxia do occur in certain tissues with ice treatment. Regardless of these outcomes, I think it is still safe to say that cryotherapy in acute injuries is beneficial, but more research needs to be completed to explain the source of the benefits.

Hailey Love said...

I think this article is very interesting as the understanding of cryotherapy continues to evolve. As more and more research in this area is published I find my explanation to athletes evolving as well when they ask why they should put ice on their injuries. As a clinician I think a critical part of our ability to treat is being able to explain to our patients what we are doing, why we are doing it, and how it is going to help them. At this point I do not think we have an adequate or sufficient answer to all of these questions in regards to cryotherapy. This is exactly the type of research we need to answer those questions for ourselves and our patients. Very interesting findings and good article.

Kimberly Rupp said...

Thanks, Hailey. As a clinician, when you apply a cryotherapy treatment, what is the rationale you give to an athlete who asks why you chose ice? I know there are many reasons we can give our athletes, but I'm always interested to hear what others use as an explanation, because as you pointed out, we don't currently have enough information to sufficiently answer these questions. Hopefully in the near future we will be better able to answer this question.

Jenna Cat said...

I believe this article can neither confirm of deny the otherwise theorized effects cryotherapy has on microvascular perfusion post acute injury. Nor can it sway my personal decision to do away with the importance of using cryotherapy post acute injury. If anything this article contributes to a piece of the puzzle that will inevitably aid in the understanding of the true effects cryotherapy has on microvascular perfusion and the role it plays in the inflammatory process post acute injury.

However I am not completely convinced that metabolic and micro-vascular effects and benefits are the main purposes of why we chose ice in the management of acute injury, although that is how we market the modality. I think the effects occurring superficially in regards to decreased cutaneous sensation, counter-irritant, or certain pain control theories need to be addressed in relation to the potential benefits of cryotherapy, such as pain reduction which I believe to play a major role in the management of acute injury.

Jessica Michel said...

This research was completed on healthy subjects, correct? Is it possible that there are different mechanisms that come into play following an acute injury? As we know, following acute injury there is immediate vasoconstriction followed by dilation and increased permeability. Do you think this alteration could be affected more by the said tissue temperature change than normal homeostatic tissue?

Kimberly Rupp said...

Jenna, you bring up a great point. Cryotherapy research, especially concerning recovery after exhaustive exercise and delayed onset muscle soreness, is inconsistent at best. Many authors state that cryotherapy has no beneficial effects on blood flow and inflammation, but is helpful in reducing subjective soreness and pain. This is what we hear most often from athletes and patient - after a cryotherapy treatment, they feel better for a short period of time! I agree that understanding changes in cutaneous sensation, regardless of the mechanism, is an important next step in cryotherapy research. If we can address the effects cryotherapy has on pain through cutaneous sensation, I think we can make better recommendations to clinicians and athletes. This would require a bit of a paradigm shift, and lead to altering the way we describe and market cryotherapy to athletes and patients. Great post!

Kimberly Rupp said...

Thanks, Jessica. You are correct, the subjects in this study were healthy. The authors used a small hypodermic needle to insert a thin thermometer into the muscle, which likely caused a small amount of trauma and a localized inflammatory response. I imagine the response after an acute injury would be more pronounced, but this small amount of trauma may be an analogue to acute injury. There is potential that the lower tissue temperature after cryotherapy treatment affects the immediate tissue response to injury - that is a hypothesis and assumed benefit that I think many health care professionals have been taught and assume to be true. A lot of the evidence in tissue response to injury and cryotherapy comes from examining the skin or the entire limb - muscle itself may respond differently though, as this study shows. It is clear that cryotherapy does something when we apply it, but what isn't yet clear is how the benefits are achieved, whether it's changes in permeability, metabolism, temperature, or skin sensation, as discussed in the previous comment. Thanks for your insight!

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