Smith machine

This is intended to make it safer for those who lift without a spotter, as one only needs to twist the wrist in order to lock the barbell in place in the event that the weight becomes too great.

[1] Bench pressing while alone is dangerous in general, but even more so in a Smith machine; if one gets trapped under the bar, it cannot be rolled or tipped sideways off one's chest or neck, which has led to at least one fatality.

[2] Use of the Smith machine is frowned upon by many strength training devotees as it forces the user to adopt an unnatural straight-up-and-down "bar path".

[3][4][5] The constrained movement of the bar also reduces the role that stabilizing muscles play versus an exercise using free weights.

[7][8] Many gyms cater to casual trainees and thus may provide Smith machines instead of power racks, which are a piece of equipment critical for safely performing squats and other barbell-based free weight exercises.

[11][12] Research published in December 2009 reported that free weights triggered 43% more activation of the muscles than a Smith machine when performing squats.