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Treating Muscle Soreness: Heat or Cold?
Len Kravitz, Ph.D.

Study Reviewed
Petrofsky, J.S., Kowailed, I.A., Lee, H. et al. (2015). Cold vs. Heat after exercise--Is there a clear winner for muscle soreness. Journal of Strength and Conditioning Research, 29(11), 3245-3252.

Muscle soreness, referred to as delayed onset muscle soreness (DOMS), results after intense or unaccustomed exercise that is beyond what is usually completed. Petrofsky et al. (2015) highlight that DOMS starts about one day following the exercise and peaks on the third day post-exercise (See Table 1 for DOMS characteristics). For over a thousand years, heat and cold have been two interventions to treat muscle soreness (Petrofsky et al), yet to this day, there is no clear understanding which is the best intervention to minimize DOMS. Petrofsky and colleagues decided to re-visit this question with a well-designed experimental study reviewed in this research column.

Table1. Characteristics of Muscle Soreness
Increased release of intra-muscle constituents (such as myoglobin) into blood
Decreased muscle strength
Physical discomfort and/or pain
Muscle cell inflammation
Reduced range of motion
Source: Petrofsky et al., 2015

Brief Overview on Cold and Hot Treatments for Reducing Muscle Soreness
Petrofsky et al. (2015) summarize that cold is traditionally applied via ice massage, cold packs or cold-water hydrotherapy. However, scientists are still trying to determine the optimal amount and duration of the cold therapy intervention. The major purpose for using cold therapy for muscle soreness is to minimize the swelling and any pain.
Heat interventions for the treatment of muscle soreness include hot packs, diathermy (a high-frequency electric current used to generate deep heat), ultrasound (sound waves used to generate deep heat) and warm water hydrotherapy. Petrofsky and colleagues summarize that heat therapy for the treatment of muscle soreness is supported because the increase of heat enhances muscle tissue metabolism, leading to a faster recovery. As well, heat therapy also lessens the pain associated with muscle soreness.

The Heat vs. Cold After Exercise Study Methods
Participants in this study included 100 healthy, non-smoking men and women (age 20-29 yrs; BMI <40 kg/m2) who were randomly assigned to either a (1) control, (2) cold packs immediately after exercise, (3) cold packs applied 24hrs after exercise, (4) heat wraps immediately after exercise and (5) heat wraps applied 24hrs after exercise. The cold therapy was applied on each leg, with the cold packs centered over the belly of the quadriceps muscle for 20min of cold. The heat therapy was also applied to each leg, with low-heating wraps centered over the quadriceps muscle and held in place for 8hrs. The authors note these are standard clinical practice therapy intervention guidelines.
All participants were not involved in any sports-like activities and had no previous training on squats. None of the subjects was taking any type of non-steroid anti-inflammatory, pain or similar medication that would interfere with muscle soreness assessment.

How the DOMS was Induced and Measured in the Participants
To produce the DOMS, all participants did three supervised bouts of squats. Each bout lasted 5 minutes with one squat being performed every 3 seconds. All soreness assessments were made pre-exercise and 1, 2 and 3 days post-exercise. One of the outcome assessments was to determine the effect the DOMS intervention had on maximal extension and flexion muscle strength of the knee (measured in a seated position) over a range of 90 to 125 degrees of motion. As well, each participant subjectively evaluated their personal pain with a 'soreness/pain' scale progressively increasing from 0 to 10 (0 indicating 'pain free' continuing to a 10 indicating 'very, very sore'). This type of scale is called a visual analog scale, which is a measurement instrument for subjective assessment of a factor (i.e., muscle soreness) that cannot be directly measured. The researchers also measured blood myoglobin, which is considered an objective biomarker for muscle soreness.

Study Results
The control group, which received no therapy after the squats, showed a 23.8% drop in muscular strength. The immediate heat and cold groups showed a small 4.5% drop in strength. Thus, both the immediate heat and cold groups significantly minimized the loss of strength due to the DOMS. The immediate heat group had slightly better results than the immediate cold group. When cold and heat were applied at 24hrs, the cold was slightly better than the heat therapy.

With the visual analog scale, as one might project, the control group experienced the greatest amount of pain, showing that no intervention is the least favorable (from a subjective observation). The least amount of pain was similarly observed in the heat and cold immediate therapy groups (although slightly better in the cold group). There was no significant difference in the heat and cold groups 24hrs after exercise.

The heat and cold immediately after exercise had the best effect for minimizing the loss of muscle myoglobin. The immediate heat group had the most positive effect on the myoglobin.

Take Home Message
Overall this research suggests that both immediate and 24hr cold and heat help to prevent muscle soreness. However, the cold therapy immediately applied after exercise or 24hrs later was better then the heat in reducing pain (as measured by the visual analog scale). For personal trainers, this may be the most telling message. A client's perceived soreness is most likely reduced best with the immediate application of 20min of cold packs to the target area. Plus, it is a relatively easy application for clients to implement.

Sidebar: Alternating Hot and Cold Water Immersion for Injury Recovery
With acute injuries, the use of whirlpools, ice packs, heat packs, infrared limps, ice massage, cryotherapy (cold treatments) and thermotherapy (heat treatments) have been utilized (Cochrane, 2004). Immediately after an acute injury the application of 20min of cold therapy is recommended because it stimulates the skin receptors to activate the sympathetic nervous system fibers to vasoconstrict, thus decreasing the swelling and inflammation. The superficial tissues will remain cold for up to 4 hours from cold-water immersion or ice packs (Cochrane). The cooling effect also helps to minimize any muscle spasms and pain.

In contrast, thermotherapy treatments increase tissue temperature, which elicit increases in muscle blood flow, muscle elasticity, local vasodilation (thus increasing blood circulation in muscle) and reduced muscle spasm. This increased circulatory response helps to clear metabolic waste products (i.e., hydrogen ions and carbon dioxide).

Presently, there is vast hearsay evidence that alternating hot/cold water contrast baths for injury treatment. The current evidence suggests that hot/cold water immersion helps to reduce injury in the acute stages. This treatment produces a vasodilation followed by vasoconstriction of the injury area, thus stimulating blood flow while also reducing swelling. Although more research is needed, several proposed recuperative and physiological mechanisms are activated that enhance the recovery (Cochrane, 2004). The most commonly practiced ratio of warm to cold bath duration for injury treatment is a 3:1 or 4:1 (3-4 minutes hot, 30-60 seconds cold). Cochrane continues that the hot bath temperatures range from 98.6 - 109.4 degrees Fahrenheit (37 - 47 degrees Celsius). The cold bath temperature range from 53.6 - 59 degrees Fahrenheit (12 to 15 degrees Celsius). The duration of the treatment is 20-30 minutes, repeated twice daily (Cochrane). Importantly, Cochrane states that a hot/cold treatment should finish with the cold treatment to encourage the vasoconstriction for the injured person. Confidently, due to increases in exercise intensities (i.e., HIIT programs) and the competitive nature of sports, future research will likely elucidate the optimal contrast ratio and water temperatures that most effectively enhance the recuperative and recovery processes.

@bio:Len Kravitz, PhD, CSCS is the program coordinator of exercise science and a researcher at the University of New Mexico, Albuquerque, where he won the Outstanding Teacher of the Year award. He has received the prestigious Can-Fit-Pro Lifetime Achievement Award and American Council on Exercise Fitness Educator of the Year.

Additional Reference:
Cochrane, D.J. (2004). Alternating hot and cold water immersion for athlete recovery: a review. (2004). Physical Therapy in Sport, 5, 26-32.