public function getWorkoutBetween(\DateTime $from, \DateTime $to)
    {
        $workouts = $this->getWorkoutsUntil($to, 1);

        /* @var $workout Workout */
        $workout = $workouts['workouts'][0];

        if (!$workout) {
            return null;
        }

        if ($workout->getStart() > $from) {
            return $workout;
        }

        return null;
    }