Do heavier boxing gloves make you punch harder, or just slow you down during training sessions?

Bigger boxing gloves, such as 16 ounces, reduce your strikes due of their weight, so they do not increase your hitting strength. Still, they boost strength and endurance, which drives your arms to work more throughout practice. In a real fight, switching to smaller gloves (say 10 ounces) after practicing with heavy ones will help your strikes feel faster and sharper. Thicker gloves are therefore great for fitness and safety during sparring, not for boosting punch power. Not glove weight, but technique and body mechanics define power.