In weight training, volume is the term used to describe how much work you do, such as the number of repetitions (reps) you perform of an exercise. Intensity describes the difficulty of an exercise, typically based on the amount of weight you lift or the pace in which you perform an exercise (such as sprints, burpees).
Broadly speaking, increasing your exercise volume improves fitness and endurance. Increasing intensity builds lean muscle mass and strength. Many researches proved that low load, high volume training as your base and intermix it with high load, low volume training to support active rest for your muscles and increase your strength to allow for progression.
In this case of deadlifts, for example, a higher volume forces your heart and lungs to work harder. As you adapt to the changes in volume, your cardiovascular fitness and endurance will improve. On the other hand, if you increase the weight of the lift and keep the reps the same, you will build muscle faster . This combination of volume (measured by duration) and intensity (measured by pace) that can help you achieve muscle growth and cardiovascular health all at the same time.
Any exercise you do will improve your fitness, endurance, muscle mass, and strength to varying degrees. Ultimately, your heart’s response to the intensity and volume of a workout will establish your fitness level.
As a general rule, the intensity of a workout is described as a percentage of your maximum heart rate (MHR). The MHR is the maximum number of heartbeats you experience during one minute of intense effort.
For a more accurate assessment, you can take a treadmill stress test under the supervision of doctor or sports physiologist. The same test can also ascertain your VO2 max (the maximum amount of oxygen your body can utilize during intense exercise). Increases in VO2 max confer to increase in lung capacity and endurance.
To improve your cardiovascular fitness, you should aim for 65% to 75% of your MHR. At this level, you are improving your aerobic fitness (your body’s ability to use oxygen to fuel workouts).
If you are exceptionally fit, you can train to between 80% and 90% of your MHR. This will place you in an anaerobic state in which your body utilizes glycogen stored in your muscles rather than oxygen to fuel exercise. While in an anaerobic state, you not only improve your heart and lung function, but you also stimulate muscle growth better than aerobic exercise alone.
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References:
https://www.t-nation.com/training/high-intensity-versus-high-volume