Which method is NOT a good way to increase training intensity?

Lowering training volume while increasing session length is not an effective method for increasing training intensity, as it can lead to a decrease in the overall workload and effort exerted during training. Training intensity generally refers to the amount of weight lifted or the level of effort exerted relative to one's maximum capability.

By decreasing the volume, such as fewer sets or repetitions, while extending the length of the sessions, you may inadvertently lower the challenge posed during each workout. This can diminish the stimulus necessary for muscle growth and strength gains, ultimately reducing the effectiveness of the training.

In contrast, the other methods listed, such as adding weights, performing exercises with shorter rest periods, and improving exercise technique, are effective strategies to increase intensity. Adding weights directly raises the load and challenge, shorter rest periods increase metabolic stress and maintain a higher heart rate, and improving exercise technique allows for more efficient and effective movement patterns that can engage the muscles more thoroughly.