A new study shows that muscles recover fastest after heavy exercise when carbohydrates are ingested and a warm bath is taken.
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Cooling or warming after exercise?
In an article about cryotherapy, I discussed the popular habit of some (top) athletes to cool down in an ice bath or in special ‘cryotherapy pods’ after a game or training session. Based on the studies discussed, I concluded that there is actually no scientific basis for this habit. Performance would not be improved, and muscle soreness would not be reduced. Recent research confirms this conclusion regarding athletic performance. In fact, according to this research, a hot bath would yield more benefits [1].
“Great!” I think. In the article about cryotherapy, I already mentioned being a bit of a wimp when it comes to cold.
New research on whether to cool or warm up
Researchers from the Karolinska Institute in Sweden and other universities decided to compare the effect of cooling down after training with warming up. They looked at the effect of this when immediate performance was required afterwards. For this, they invited five fit, young men and women to a human performance lab and had them train with a device where you “cycle with your arms”. Participants had to perform a series of short but exhausting intervals followed by 20 minutes of continuous moderate-paced training. Heart rate and generated power were measured during this.
This protocol was followed to exhaust the arms as much as possible.
Part of muscle exhaustion can be easily explained by the depletion of glycogen in the muscles (stored glucose). When this fuel runs out, the body has to switch to energy that is delivered more slowly, such as fatty acids. Therefore, participants were asked to ingest large amounts of carbohydrates in the two hours after training. After this, the interval part of the training was repeated to see the difference in generated power.
Participants were asked to come back two more times. However, this time, in the two hours after the first training, besides consuming carbohydrates, they were also cooled or warmed. This cooling or warming was done using a type of sleeves that were cooled to 15 degrees or warmed to 38 degrees using a liquid.
Ultimately, the researchers compared which intervention (carbohydrates alone or combined with cooling or warming) resulted in the least loss of power. Warming the arms came out as the winner. Cooling, on the other hand, led to the greatest loss of power.
Improved carbohydrate uptake after warming up
Next, the researchers went a step further. They wanted to know why warming up yielded the best results. To investigate one hypothesis, they then moved on to muscle fibers obtained from the leg muscles of mice.
These fibers were attached to a mechanism that can measure the strength of contractions. These contractions were stimulated by electrical stimulation so that they continuously contracted and relaxed. When the speed of contractions decreased, this was seen as exhaustion. After this exhaustion, some of the fibers were supplied with glycogen. All fibers were then either warmed or cooled. Finally, all fibers were put back to work by electrical stimulation.
Two differences with the human study:
- They also looked at the effect of cooling and warming without administering carbohydrates/glycogen
- They could measure how much glycogen was absorbed by the muscles after the intervention
The researchers observed that once again, warming up led to the least loss of power. However, this was only the case when the muscles were supplied with glycogen. The researchers therefore concluded that warming the fibers resulted in better absorption of the administered glycogen by the muscle fibers.
Limitations of the study
There are a number of caveats to be made about this research. For example, the first part with the athletes was conducted with a very small number of participants. It would also have been useful if there was a protocol where no carbohydrates were ingested after the training.
We can’t compare that scenario now.
Possibly more importantly: For the study, they looked at the effect when you have to perform again after 2 hours. This may be useful for some sports where you have to perform multiple times on the same day. However, for the vast majority of athletes in general, it will only be necessary to use the same muscles again at most the next day. I can imagine that by doing this on the same day, the differences are clearer. The difference in strength will then be greater than if you had a day to recover.
However, in practice, this could lead to a different result. After all, we are not only talking about cooling down and warming up after the first training session, but we also have to take into account the effect of this on the second training session. Normally, you wouldn’t want to cool down immediately before training, that’s why we use a warm-up. So, I can imagine that an effect on recovery is now exaggerated by the direct effect of cooling down and warming up on the second training session. Normally, you take an ice bath after training and you don’t start action until the next day when you have long since returned to your normal body temperature.
References
- Cheng AJ, Willis SJ, Zinner C, Chaillou T, Ivarsson N, Ørtenblad N, Lanner JT,Holmberg HC, Westerblad H. Post-exercise recovery of contractile function and endurance in humans and mice is accelerated by heating and slowed by cooling skeletal muscle.
- J Physiol. 2017 Oct 4. doi: 10.1113/JP274870. [Epub ahead of print] PubMed PMID: 28980321.
