Meb Keflezighi (right, winning the 2009 NYC marathon) credits much of his success to icing.
About a year ago I met Meb Keflezighi, one of the greatest American marathon runners of all-time, while training at Mammoth Mountain in California. Since then the 37 year-old stud has had a very successful season culminating in a fourth place finish at the 2012 London Olympics. During our meeting he stressed the importance of icing on his success. Therefore, I was not too surprised that Meb emphasized his devotion to icing during media interviews after winning the 2012 American Olympic marathon trials. Meb is unquestioably one of the world's most elite marathon runners. However, the question reains: What part has icing played on Meb's running career?
Although studies looking at the effects of icing, or cryotherapy, have had somewhat conflicting results, most studies have found icing following exercise-induced muscle damage to be beneficial. The extent of muscle damage peaks between 24 and 72 hours following strenuous exercise. Exercise-induced muscle damage includes sarcolemma disruption, fragmentation of the sarcoplasmic reticulum, lesions of the plasma membrane cytoskeletal damage and swollen mitochondria. Outside the muscle fiber there may be swelling due to an increase in blood flow and capillary permeability.
One study looked at the multi-day effects of icing on exercise-induced muscle damage (Effects of cold water immersion on the symptoms of exercise-induced muscle damage, 1999, Roger Eston and Daniel Peters). The study used 15 female subjects and endurance exercised their biceps. The cryotherapy group submerged their exercised arm into a tub of 15 degrees Celsius water for 15 minutes. This treatment was administered immediately after the bout of exercise and every 12 hours thereafter for 3 days.
The study results show that creatine kinase activity, a predictor of muscle damage, was lower in the cryotherapy treated group two and three days after the bout of exercise. The graph below shows these results.
Eston and Peters also showed that the arm circumference and tenderness were not significantly affected. However, arm strength returned to baseline much faster in the cryotherapy group. This is of particular interest to athletes who often are expected to complete consecutive workouts in a 72 hour timeframe. The difference was significant: after 72 hours the control group had a mean isometric strength that was 86% of baseline while the cryotherapy group had a mean isometric strength that was 111% of baseline.
A more recent study on the subject of icing measured blood flow, temperature and muscle endurance in cryotherapy treated and control groups (Changes in Blood Flow, Temperature and Muscle Endurance in Association with Cryotherapy, 2009, Masahiro Utsunomiya, et al.). In this Japanese study three groups were established: resting group (10 minute rest), 2-minute cooling group (2 minute icing and 8 minutes of rest) and 10-minute cooling group (10 minutes of icing). Endurance was significantly boosted by icing. After ten minutes of rest the resting group performed at 59.2% of the initial test, the 2-minute cooling group 73.1% of initial test and the 10-minute cooling group 80.7% of the initial test. This suggests that the effects of icing are immediate. Decreases in deep part temperature and tissue circulating volume were also observed as duration of icing increased.
The authors suggested that the cooling decreased oxygen consumption and cellular metabolism. This would potentially increase muscle endurance. However, an EMG signal processed with Fast Fourier Transformation saw no significant differences between the groups during the second bout of training. The authors hypothesized that the lack of significance means differences in endurance could have been the result of lowering myogenic pain instead of an increase in physiological fatigue.