Researchers discovered that even as little as nine days of intense training can cause 'significant and progressive decline in sleep quality'. (Representational Image)
Intensive bouts of exercise may cause significant and progressive decline in sleep quality and worsen your mood and capacity for exercise, a new study in athletes suggests.
Scientists from Loughborough University in the UK studied the effects of two nine day periods of heavy training on 13 highly trained cyclists.
The researchers monitored the athletes' moods, sleep patterns and performance before, during and after exercise.
To determine whether diets could counter the effects of any sleep deprivation, the athletes were also given high or moderate amounts of carbohydrate throughout the study, though none of them knew which.
The researchers discovered that even as little as nine days of intense training can cause 'significant and progressive decline in sleep quality'.
They also noticed that the athletes' moods and capacity for exercise both worsened over the period of observation.
The data collected also indicated that the cyclists spent more time in bed during the intense training - suggesting that they were indeed tired. But the extra time under the covers did not result in any more actual sleep.
"Sleep efficiency was significantly reduced during the intensified training period," the researchers observed, and the number of times the athletes woke throughout the night significantly increased.
In addition, the cyclists reported changes in their moods as the study went on, including higher tension, anger, fatigue, confusion, depression and increased feelings and symptoms of stress.
The researchers found that a high carbohydrate regime reduced some, but not all, of the effects of hard training.
The moderate-carb athletes recorded more sleep time, but this may demonstrate higher levels of fatigue and a greater need for recovery when following that diet.
"The cycle of successful training must involve overload to a state of acute fatigue, followed by a period of rest. If overloaded training is not followed by sufficient rest, overreaching may occur," the researchers said.
The findings were published in the Journal of Sports Sciences.