Lifting weights for just three seconds a day is enough to build muscle.
It has been found that a single repetition of maximum effort, five days a week for a month, increases the strength of the biceps by up to 12%.

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Demonstrate that out-of-state people or the elderly can get stronger without long gymnastics sessions, the researchers say.
Professor Ken Nosaka said: “If we find that the three-second rule applies to other muscles, you may be able to exercise your whole body in less than 30 seconds.
“Also, performing a single maximum contraction a day means it doesn’t hurt.
“Many people think that you have to spend a lot of time moving, but this is not the case. Short, high-quality exercise can still be good for your body. ”
The findings come from tests on 39 unfit students.
They only performed a biceps bend once a day for five days a week for four weeks.
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It meant that they did a total of only 60 seconds of weight lifting in 20 sessions.
Professor Nosaka, from Perth, Australia, added that mini-training could prevent weakness and fragility in old age.
He added: “It can prevent loss of muscle strength due to disease, sedentary lifestyle and space flight.”