Just think about it, what will happen if he used a battle skill inside a confined space? Yang Chen didn't want to accidentally break things by practicing attack skills and the room was far too small to practice any movement skill.
So was it impossible for him to practice any battle skill inside the room? That was not true, sensory type battle skills like the [Boundless Nature's Eyes] could still be practised and so were some of the defensive type battle skills.
Among the three battle skills that he got from Lin Mang, He couldn't practice the [Lion's Roar Fist] and the [Extreme Lightning Movement] but it was still possible for him to practice the [Swift Flowing Deflecting Palms].
The [Swift Flowing Deflecting Palms] was a set of gentle palm movements that redirected the force of the enemy's attacks and used it against them.
If you like the novel.. throw some power stones and Golden Tickets towards this way... Much Appreciated.