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Patient-identified phenomenon confirmed in GSD5.

Four posters on McArdle’s were presented at the World Muscle Society Congress in Copenhagen early in October. One in particular stood out for us, as the study behind it arose out of experiences on the AGSD-UK “Walking with McArdle’s” courses.

Shared experiences on walking courses

Over 9 years, many of the course participants have shared their feeling that they were much better later in the day than they were shortly after getting into “Second Wind”. A few of the course participants reported that this change seemed to happen after about 40 minutes of walking, but most could not pin it down to a particular timescale.

Whatever the timing of it starting, all agreed that they definitely felt really good at the end of a day’s walking. Some reported that when they walked with non-McArdle friends, at the end of the day their friends would be tired and wanting to relax, whereas they would be feeling ready for more.

Could there be a Third Wind?

We started to term this the “Third Wind”. Of course, there were suspicions that perhaps the phenomenon might be psychological in nature, so we hoped that it could be fully investigated. There was no hint of evidence of such an effect in the medical literature, and indeed several leading McArdle experts around the world assured us that there was no such effect.

Walking on to the treadmill at the Brunel University exercise lab.

A study is planned

However, in discussing the reports from course participants with Dr Richard Godfrey, senior lecturer at Brunel University and the exercise physiologist working with the UK McArdle clinic, it was agreed to undertake a research study to try to identify whether such an effect was real.

A masters student was selected to conduct the research, and AGSD-UK helped to recruit participants for the study and contributed to the costs.

A group of McArdle patients and a control group were asked to walk on a treadmill for 2.5 hours, non-stop at a self-selected pace. Blood tests, heart rate, perceived exertion, and expired gas were analysed. The expired gas revealed the amount of energy being utilised from carbohydrate and fat.

Evidence starts to emerge

You can see from the graphs above that we now have evidence of energy utilisation having a very different pattern in McArdle people to unaffected people (the control group). There are very distinct changes at the 31 minute mark and the 121 minute mark, both being long after the 8 minute mark typical for the start of “Second Wind”.

McArdle people have an initial surge in energy from carbohydrate (glucose released from the liver), but that drops off rapidly and by minute 151 fat is providing about 2/3rds of the total energy. Whereas for unaffected people at minute 11 they have 90% of energy from carbohydrate (mainly muscle glycogen) and that gradually drops off as fat utilisation increases, until at minute 151 energy utilisation is roughly equal from carbohydrate and fat.

This work will now be carefully studied and hopefully will eventually result in this “Third Wind” phenomenon being fully understood, so that it can be explained to patients for them to use to good effect.

Thanks for the support

Many thanks to the six McArdlites who bravely participated in this study, knowing that they faced walking for 2.5 hours absolutely non-stop (not even for a toilet break!), though they were allowed to chat and to watch TV. Thanks also to staff and students from Brunel University and the McArdle Clinic who were so committed to this project.

Download a PDF of the WMS “Third Wind” poster.