Daily singing workout keeps songbird males attractive

Every year in the Christmas season it becomes clear again that some people are amazingly skilled singers, like Mariah Carey and George Michael. Their singing can stir strong emotions.

Singing involves probably the most complex, and mostly hidden, movements humans and animal can make. To become a good singer, you need to learn how to coordinate the movements of hundreds of muscles in your body with extreme precision. Therefore, you need a lot of talent, and practice.

We all know that athletes invest a lot of time exercising their limb and body muscles, but how about training the muscles in your voice box?

- Surprisingly we know very little about effects of exercise on these muscles and if they even react to training in humans. No singer will let you come even near their precious voice box, says Professor Coen Elemans, an expert on sound production.

Together with assistant professor Iris Adam, he has led a study of song production. The study is published in Nature Communications. Co-authors are from Leiden University, University of Umeå and University of Vermont.

The study reports that male songbirds need to sing daily to exercise their vocal muscles and produce pretty songs. And the females notice if they don’t.

A male zebra finch sings for a female at Dept of Biology, SDU. Film: Susan Grønbech Kongpetsak/SDU.

Weaker within days

- Singing is crucial for songbirds. They sing to impress future partners, to defend their territories and to maintain social bonds, says Dr. Iris Adam, lead author of the study.

- It has long been known that songbird singing is controlled by fast vocal muscles, but until now we only had very little knowledge if and how these muscles might respond to exercise, like our leg muscles do, says Iris Adam.

In their study, the researchers show that if songbirds don’t use their vocal muscles at all, they get much slower and weaker already within days. But even when the birds only skip singing, after 7 days the vocal muscles already lost 50% of their strength.

Use it or lose it

- This was very surprising, says Dr. Adam. -First that these muscles reacted so strongly, but also how incredibly fast they lost performance. Indeed, it’s use it or lose it!

When analyzing the songs sung, the team found that the birds sang differently before and after exercise.

- You and I could barely hear a difference between the songs, but we saw clear effects when we analyzed our song recordings, says Dr. Adam.

What did the females think?

As the ultimate test if this difference was important to the birds, the team next played songs to female zebra finches to ask them if they could hear a difference between before or after exercise, and which song they liked more.

- The female zebra finches in the playback experiment could directly hear the difference and 75 percent preferred the songs from the well exercised male, says associate professor Katharina Riebel of Leiden University, co-author on the study and an expert in animal behavior.

When studying the zebra finch vocal muscles, the team made another very important discovery.

The same may be true for humans and other animals

- When we humans go to the gym to exercise leg and arm muscles, they typically get slower with exercise, says professor of anatomy at University of Umeå, Per Stål, co-author on the study and an expert in muscle exercise physiology in humans.

However, in songbirds vocal muscles don’t get stronger and slower with exercise, like limb muscles, but weaker and faster. This is opposite from normal limb and body muscles.

- This reversed training may be a unique feature for vocal muscles, that we think might be true for all vertebrates, including humans, because all vocal muscles are developmentally related, says Iris Adam.

Implications for speech therapy

- Therefore, these findings can have major consequences for speech therapy and vocal training in humans, says Coen Elemans.

Because it’s so challenging to study the physiology of human larynx muscles, therapeutic intervention is based on what we know from exercise physiology of leg muscles.

- However, training vocal muscle may thus work very differently, says Elemans, adding that:
- Songbirds may be our best allies to study the physiology of vocal muscle to further improve voice training and rehabilitation in humans.