The timing of different segments of a workout can have a strong effect on your performance and the results. When training for boxing, the question of whether to hit the weights before or after your practice session is a matter of your goals for that day.
Effects of Weight Training
When you train with weights, it affects your muscles and your overall energy level. Resistance training actually tears your muscles with each lift. Your muscle fibers grow thicker and stronger by repairing these tears. While you're lifting, your body also floods the area with blood. This draws oxygen from other systems, causing your heart and breathing rate to increase in order to keep up with the increased demand. The combination of these two effects pushes your body to fatigue.
Fatigue is the state your body enters as it reaches the limits of its endurance. Effective weight training intentionally pushes your body to this state. According to the European Road Safety Observatory, fatigue reduces alertness, increases reaction time, limits attention span and interferes with processing and storing information. In other words, anything you do after becoming fatigued, you're going to do less effectively and derive less benefit from.
Lifting After Training
Since fatigue limits your ability to perform many of the tasks important to success in a session of boxing training, it's better to do your weight training afterwards. Martial arts coach David Coffman says this is especially true if your training session will involve learning or reinforcing new combinations or any kind of strategy planning. Your senses and your comprehension need to stay sharp while you're learning something new.
Lifting Before Training
According to Coffman, there is one reason to do your weight lifting prior to training: building endurance. To maintain good form and throw solid punches when you're fatigued, you have to practice your punches and form while fatigued. By lifting weights or doing other vigorous exercises prior to your training session, you put yourself in a state in which you practice while fatigued. This mimics the condition you'll be in during the later rounds of a fight, an experience that's invaluable to newer fighters.
Coffman recommends lifting weights before training on some days, and afterwards on others. This allows you to be fresh for some sessions, while still benefiting from beginning some sessions fatigued. Coffman further advises that you should come fresh to sessions that require higher-order thinking skills, such as practices where you learn new combinations. Come fatigued to sessions that emphasize the physical, such as conditioning and sparring.