Which of the following strengthening exercises requires a spotter?

The bench press with dumbbells requires a spotter because it involves lifting weights overhead while lying on a bench, which can pose a risk if the lifter loses control of the weights. The spotter's role is to assist the lifter in case they struggle or fail to lift the weights, providing safety and preventing injury from a dropped weight. This exercise, in particular, involves significant weights that can fall toward the lifter's face or chest, making it crucial to have someone present to help.

The other exercises listed do not typically require a spotter for safety. The overhead triceps extension can usually be performed safely with lighter weights without assistance, while the seated leg press is a machine-based exercise that provides support and safety features, eliminating the need for a spotter. Similarly, the standing calf raise, often done with a relatively manageable weight, typically does not require the assistance of a spotter. Thus, the bench press with dumbbells stands out as the exercise that necessitates a spotter for safety during execution.