When it comes to exercise, an approach that's able to achieve the same results with less effort sounds too good to be true – but that's what researchers have discovered in an analysis of exercise techniques and subsequent changes in muscle strength and size.

The new study looked at three different types of dumbbell curl exercise: eccentric (lowering weights, lengthening the muscle), concentric (lifting weights, shortening the muscle), and both concentric and eccentric together (alternately lifting and then lowering weights in the same exercise).

While all these exercises improved concentric (lifting) strength, only the eccentric and concentric-eccentric exercises also improved eccentric (lowering) and isometric (static) strength.

What's more, the improvements in the group doing lifting-and-lowering exercises were about the same as those in the group doing lowering exercises only – or half as many reps.

"This latest study shows we can be far more efficient in the time we spend exercising and still see significant results by focusing on eccentric muscle contractions," says exercise and sports scientist Ken Nosaka from Edith Cowan University in Australia.

"In the case of a dumbbell curl, many people may believe the lifting action provides the most benefit, or at least some benefit, but we found concentric muscle contractions contributed little to the training effects."

In other words, the eccentric muscle actions achieve the same results as the concentric-eccentric exercises, even though the technique takes half the time. The eccentric-only exercises also scored highest in terms of muscle thickening.

The results were based on four groups of people: 14 people doing concentric exercises, 14 people doing eccentric exercises, 14 people doing concentric-eccentric exercises, and a control group of 11 people not doing any exercises. The exercise routines were carried out twice a week for five weeks, with 3 sets of 10 repetitions each time.

Based on the results, the researchers suggest using two hands to lift weights up into position before switching to one hand for eccentric (lowering) actions in exercises such as bicep curls and overhead extensions. The study authors say the same principles should also extend to leg exercises.

"We already know only one eccentric muscle contraction a day can increase muscle strength if it is performed five days a week – even if it's only 3 seconds a day – but concentric or isometric muscle contraction does not provide such an effect," says Nosaka.

Simple eccentric exercises without dumbbells should also prove effective, Nosaka says. They can include slowly lowering yourself onto a chair or putting your hands on a wall in front of you and slowly leaning into it as your arms bend. There are some more examples of these exercises here.

According to the researchers, it's possible that eccentric exercises provide more stimulus to the muscle fibers in return for the same or even less effort, which would explain the results here, but more research is required to know for sure.

Only adults with minimal weight training experience were involved in the study, so future studies could look at whether the same benefits apply to other, older age groups and already-active individuals, as well as different muscle groups.

The overall message is that exercise can make a difference even if it's limited in terms of repetitions, technique, and time; you don't have to spend hours at the gym each week to strengthen muscles and improve fitness.

"Understanding the benefits of eccentric-focused training can allow people to spend their time exercising more efficiently," says Nosaka.

"With the small amount of daily exercise needed to see results, people don't necessarily even have to go to the gym – they can incorporate eccentric exercise into their everyday routine."

Because, as past research shows, frequent exercise is likely key to finding the optimal exercise routine. So whatever exercise you do, do it often.

The research has been published in the European Journal of Applied Physiology.