Regular cardiovascular training has many benefits - most of which, of course, are health related.
Cardiovascular fitness is also of interest to people who strength train. The better your cardiovascular fitness, the faster the body recovers between sets and the more exercise you can do in a training session.
Weights Over Endurance Training
Lots of people who like working out in a gym are not really fans of endurance training. This leads them to question whether or not they can replace endurance training with strength training if the use more repetitions using less weight and taking short breaks between sets. Another reason endurance training is not always ideal is that it doesn't encourage muscle growth.
The Answer to the Weight Lifting vs Cardio Question
A study addresses this question!
For this study, 16 powerlifters who had been weight training for at least two years were divided into two groups. In addition to strength training, one group spent two weeks weekly doing HIIT sessions on a bike for eight weeks. Their routine went like this:
Warm up for 5 minutes between level 6 of 10
Do seven 30-second sprints between levels 8-9; in between sprints, do 90 seconds at a level of 5-6
Ride 5 minutes at level 4-5
The other group did a HIIT session twice a week in addition to strength training, once with deadlifts and squats. The group did so seven sets with so many repetitions that the subjects could just do one or two repetitions at the end. Between the sets, the participants took a 90 second break. To cool down they did 5 minutes of cool down walking on a treadmill.
The study showed that both groups gained the same amount of strength. In addition, the VO2max increased in both groups, with noticeable differences: in the group that completed HIIT exercises on the bike, noticed a greater VO2max increase. This suggests that as a competitive athlete looking to improve your cardiovascular performance, you'd be better off doing HIIT on a bike.
Additionally, the study noticed that HIIT units with squats or deadlifts reduce the overall maximum weight you can lift as you need to take breaks to let your muscles rest. While cycling, you don't need as much recovery time.
Last but not least, we also have to consider the risk of injury: doing deadlifts and squats in quick succession with a high number of repetitions and many sets is more likely to result in an improper form. This in turn increases the probability of injury. When cycling, you are not as likely to have this problem.