New research has revealed almost 20 per cent of people worldwide lack a protein called α-actinin-3 in their muscle fibre.
The skeletal muscle in this group of people is made up of more slow-twitch muscle fibres. These muscles are more durable and energy efficient and provide better tolerance to low temperatures than fast-twitch muscle fibres.
Slow-twitch muscle fibres are more resistant to fatigue, while fast-twitch fibres tire more quickly.
The researchers at Karolinska Institutet in Sweden believe α-actinin-3 is absent due to a mutation in the gene that codes for it. It is believed the gene increased when humans migrated from Africa to colder climates in Europe.
Professor of cellular muscle physiology at the Department of Physiology and Pharmacology at Karolinska Institutet, Håkan Westerblad, says the mutation probably gave an evolutionary advantage during the migration to a colder climate.
“In today’s modern society this energy-saving ability might instead increase the risk of diseases of affluence,” he says.
The study was conducted on 42 men aged 18–40. They sat in cold water until their body temperatures had dropped to 35.5°C, and then the researchers measured muscle electrical activity with electromyography (EMG) and took muscle biopsies to study the protein content and fibre-type composition.
Another interesting aspect of the research showed that people who lack α-actinin-3 have a greater capacity for endurance sports, but often fail at sports requiring strength and explosiveness.
Professor Westerblad says there hasn’t been any direct experimental evidence for this before.
“We can now show that the loss of this protein gives a greater resilience to cold,” he says.
A German study in 2019 found that male and female office co-workers perform more efficiently at different temperatures. Women were found to perform significantly better in warmer temperatures, while the reverse was true for men.
Could a lack of α-actinin-3 also play a part in mental performance?
The Karolinska Institutet notes that one limitation to the study is that “it is harder to study mechanisms in human studies at the same level of detail as in animal and cell experiments”.