When I look for best ways to train and gain I always come across the same words which are continuous, interval, fartlek, circuits, plyometric and strength training.
I find these exercises can really work you hard cardiovascularly if you know what your doing or get the right trainer. Cardiovascular has multiple benefits in muscle, tendon and bone healing. Don't forget when you put bone structures under heavy loads it can cause micro fractures which won't impact the integrity of the bones matrix and stability but is the reason why you can ache for long periods after heavy training sessions. This inevitably makes the bone stronger and able to tolerate greater forces. It also helps with life expectancy (lol), recovery, HR, BP, metabolism, and hormones.
When I started I forgot about cardiovascular exercise as it had a massive impact on my strength training as I only did it in short burst on and off and never gave myself a chance to accommodate to the different exercise. But if you want your body to utilise your diet the most efficiently you need CV in your training. Also exercise in general will increase your bodies ability to increase your endorphin level which is based In your pituitary gland and spread through your nervous system. When released Endorphins can reduce pain, stress, release sexual hormones and the best effect of all the feeling of euphoria. Which is why you can feel good after training. Both pain and stress can impact you diet and strength gains by suppressing your need to eat. Importantly any form of exercise releases endorphins so it doesn't matter which type you do.
So continuous is gives the best benefit from cardiovascular fitness and it is as simple as carrying out an exercise for long periods of time with no rest. This primarily will work your slow twitch muscle fibres which rely on oxygen to reboots the energy stores/ATP in the muscle cell. To get benefits from this you need to carry out continuous exercise for a minimum of 20 minutes at about 60% of your max HR, 3-4 times a week. Although continuous training has its benefits this isn't particularly helpful in strongman as we tend to carry out events in bursts of 1-2 minutes.
Interval, circuits and fartlek are the same in the way, as they are alternate burst based exercise either from station to station or post to post. Interval training is bursts of hard exercise followed by periods of rest. E.G. 400m sprints followed by walking 400m and then repeat or swimming under water the length of a pool and then rest and repeat. You have to set a pace and stick to the pace each time which is what I find difficult to keep.
Circuits is where you go around 6-10 different stations where you focus on a particular muscle group/s for periods of 1-2 minutes. I remember at university we were trained by a navy fitness instructor who use to leave a bucket in the middle of the room and guard entered we would all use it! He was right we all did. Very effective on boosting your CV in the gym environment but equally this isn't going to make you strong or big as you'll lack the energy to train your strength effectively.
Fartlek is where you vary your speed at interval bursts. E.G. 10 metre square where you walk 10m, jog 10m, run at 3/4 pace 10 m and sprint 10 m and repeat. This is good for both boosting your anaerobic and aerobic CV fitness.
The rest periods between these are what differs these exercise and changes the use from your slow twitch fibres to your fast twitch. In order for your glycogen stores to restore and your ATP to regenerate from ADP your body needs 45-60seconds. So it's interval yu would rest for a minute between sets but with fartlek it's the time your walking and jogging so your never completely resting which is why it's the hardest of the 3 and circuits you get a rest of 20-30 seconds or as long as it takes to get set up at the next station.
Out of the 3, interval training is probably the best form, where you look at repetitive movement and it has the most carry over for strongman events. Repetitive movements are the best, for not only CV fitness but improving your central and peripheral nervous system by speeding up the rate at which the nerve stimulate the muscle fibres. This type of CV also boost type 2b/fast oxidative muscle fibres which are what you predominantly need when your repeatedly lifting heavy weights.
Strength training is what strongmen do about 90% of the time (everyone is different, so sometimes people respond better to more or less cardio) and this is where you work fast twitch muscle fibres/ type 2a. These muscle fibres are the largest of all 3 and use practically no oxygen when it contracts , so as expected it exhaust faster than the other fibre types. In a workout this is your 5sets of 5 repetitions or your 3 sets of 3 reps. When using the fast twitch you can go up to 8-10 reps but you will get cross over between your fast twitch and fast oxidative.
For powerlifting you would typically stick to strength training with a dominance in the low rep range, long rest, and high amount of sets which is the same as weightlifting. This is because their training is based around power movements which exhaust muscle quicker and require longer rest periods. Rugby players will tend to use strength, fartlek training and circuits because their sport is very fast paced and their rest periods are short between rucks and mauls, but they need the strength for speed and power in the scrums, rucks, tackles, etc. Strongman is a sport where it's a combination of CV, Power, Strength and endurance on 1 day competitions. So its difficult to train all 3 and expect gains so I mostly use interval training with strength training and will use power based movements in the basic lifts like deadlift, squat and press.
How you train will have an impact on your performance so you need to make sure your training right.