public function toString()
    {
        if ($this->getTime() !== null) {
            $time = $this->getTime()->setTimezone(new \DateTimeZone('UTC'))->format('Y-m-d H:i:s \U\T\C');
        } else {
            $time = '';
        }
        return $time . ';' .
            $this->getInstruction() . ';' .
            $this->getLatitude() . ';' .
            $this->getLongitude() . ';' .
            $this->getDistance() . ';' .
            $this->getSpeed() . ';' .
            $this->getAltitude() . ';' .
            $this->getHeartRate() . ';' .
            $this->getCadence() . ';' .
            "\n";
    }