Smartphone app keeps eye on Hertha Berlin stars' sleep

Since the beginning of the season Hertha's stars, such as former Chelsea striker Salomon Kalou, have to answer a short questionnaire each morning.

Using their smart phones, players must rate their level of fatigue, sleep quality, muscle soreness, stress levels and mood condition.

The players rate each category from one (worst) to five (best) and the questionnaire takes around 15 seconds to answer.

"It's so we can learn how the boys slept, whether their legs hurt or their muscles are cramped," Hertha coach Pal Dardai told German daily Bild.

The information goes to the club's fitness coach Henrik Kuchno.

"At 8am (0700 GMT), each player gets the five questions on the phone, which he has to answer by 9am.

"It's so we can control the subsequent training sessions perfectly and know the degree of stress of each individual."

Kuchno rejects the notion that the app keeps tabs on a players lifestyle, "it's not about monitoring the players".

Training sessions are then tailor-made to get the best out of the players and provides a 'personal picture' of how each player is.

"We depend on the honest opinion of the players, of course," added Kuchno.

"Naturally, a family man answers the questions differently than a bachelor."