Volume equals total reps, sets, and load in a given training session. High-volume multiple-set programs are shown to be superior over single-set routines to increase muscle mass. While the exact mechanism isn’t known, greater hormonal responses (acute testosterone and growth hormone elevation) occur with higher-volume multiple-set protocols compared to lower-volume protocols. For hypertrophy, more does appear to be better, and the higher-volume work more effectively spikes hormone responses. Gradually increase your volume over time in a methodical way. Your plan should also include shorter deloading periods to avoid overtraining.
Both multi-joint and single-joint exercises are useful for building muscle, but multi-joint movements are superior in this regard. Multi-joint exercises are the ones in which more than a single pair of joints are working during a given exercise. For instance, when bench pressing, the shoulder and elbow joints—and the muscles that attach to them—come into play.
There’s no question that multi-joint exercises recruit a greater degree of muscle mass, stimulate a greater hormonal response from training, and stimulate the nervous system to a greater extent than single-joint moves do. Including both types of movements is important to maximally develop the target muscle. Varying exercises allows you to stimulate more muscle fiber recruitment, essentially working the muscle from different positions, planes and angles.