EMPLOYEE WAS ON A LADDER APPROX 3' ABOVE GROUND. MAINTENANCE WORK WAS BEING PERFORMED ON A GRAVEL CHUTE. THE EMPLOYEE REACHED OUT AND THE LADDER SHIFTED. IN THE PROCESS OF STABALIZING THE LADD ER AND HIMSELF THE EMPLOYEE STRAINED HIS LOWER BACK. THE EMPLOYEE COMPLETED HIS SHIFT AND THE BACK STIFFENED UP OVERNIGHT!