The amount of force a person can exert depends on many variables, including that person's mass, the acceleration being used to exert the force, and the friction, gravity and other forces involved. According to Live Science, researchers found that boxers' punches can generate up to 5,000 newtons of force.
Five thousand newtons of force is more than the force exerted down upon the Earth's surface by a half-ton. Most people do not generate nearly that much force. According to the Canadian Centre for Occupational Health and Safety, a worker supporting his or her body against a firm structure can develop horizontal pushing or pulling forces of up to 675 newtons,