Scientists in Florida have found that, to get the greatest benefits from exercise, people need to up the intensity

Over the last few years, there’s been much focus on the benefits of short bursts of intense exercise – namely high intensity interval training (HIIT). Indeed some workouts such as Tabata claim to deliver results in just four minutes.

This might all sound too good to be true, but an interesting new study from the Florida campus of The Scripps Research Institute (TSRI) in the US shows that intense exercise has an impact on the muscles and the body at a molecular level that doesn’t occur in milder forms of physical activity. Although the study was based on changes in mice, the findings add to a growing body of evidence which suggests that, if people want fitness results, they must push themselves beyond their comfort zone.

CRTC2 release
The study, published in molecular biology title The EMBO Journal*, is one of the first to look at the effect of high-intensity exercise at a cellular level.

Scientists have known for some time that the body’s sympathetic nervous system – or the ‘fight or flight’ response – is turned on during exercise, specifically during intense workouts. The general consensus was that there were no other benefits besides a short-term kick-start, but the team at TSRI thought differently and focused on a protein called CRTC2 to prove otherwise.

CRTC2 – which is released during intense exercise – integrates signals from the adrenalin and calcium pathways and has a direct impact on the muscles that are being used. For the study, the scientists bred mice with genes that would produce much more CRTC2 when faced with a two-week strenuous physical activity programme.

The genetically modified animals saw a 15 per cent increase in their muscles. Metabolic parameters, indicating the amount of fuel available to muscles, also improved substantially – triglycerides went up 48 per cent, while glycogen supplies rose by a startling 102 per cent.

In addition, the endurance in the genetically modified mice soared. It went up by 103 per cent in the exercise stress test, compared to only an 8.5 per cent improvement in the mice who did not have the enhanced CRTC2 protein.

Exercise enhancements
The findings open the door to potential exercise enhancements, says Michael Conkright, a TSRI assistant professor and the study’s lead author. “The sympathetic nervous system gets turned on during intense exercise, but many had believed this wasn’t specific enough to drive adaptations in exercised muscle.

“Our findings show that not only does it target specific muscles, but it improves them – the long-term benefits correlate with the workout intensity.”

The study highlights the importance of ongoing workout programme assessments in health clubs. Conkright told the New York Times that, once someone reaches a fitness plateau, the sympathetic nervous system is not stimulated, adrenalin is held back so the CRTC2 protein is not activated, and changes in the body will not be so great.

What he does say, however, is that “intensity is a completely relative concept” – a brisk walk might be enough of a push for someone who’s not fit, but it wouldn’t cut it for a regular gym-goer.

Staff scientist Nelson E Bruno, who worked on the study at the Conkright laboratory, adds: “Nothing can supplement exercise. However, just by activating one protein, we clearly improved performance in animal models.

“We’re now searching for molecular therapeutics that will activate the CRTC2 protein, so that even an average exercise routine could potentially be enhanced and made more beneficial.”