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Dynamic (Eccentric & Concentric) Exercises and the Muscle Fibres Involved

Updated: Jul 11, 2020

Before reading any further: Please read our Dynamic vs Static Exercises: Which is Best blog post first! As your read in the blog mentioned above: Strength training involves three different actions that cause your muscles to produce force namely Dynamic (eccentric & concentric) exercises and Static (isometric) exercises. Contrary to dynamic exercises, static / isometric exercises create no change in the length of the muscle. Research has shown that isometric training can lead to static strength gains. Ie. for starters being able to hold a plank for 30 sec and gradually working your way up to be able to hold it for a minute or two. According to the ACSM (American College of Sport Medicine) current research, it's recommended that people who wish to include isometric actions as part of their strength training routine - should perform multiple positions of the contraction to ensure full ROM strengthening. If you have any questions regarding static / isometric exercises, pop us a mail or leave a comment below! So back to dynamic exercises! When force is used to overcome an external load - such as lifting a weight - and the muscle is shortened / contracted, the action is referred to as a concentric movement. When force is used when the muscle extends / lengthens, the action is referred to as an eccentric movement. It's actually super easy and logical to remember: Contract = Concentric Extend = Eccentric Let's put it in perspective by using an example: When performing a basic bicep curl - when you bend your elbows and lift the weights towards your chest - your muscles shortens / contracts - thus the concentric phase. When you lower your arms back down to the starting point - your muscles lengthens / extends - thus the eccentric phase. Thus, dynamic exercises have both a concentric as well as a eccentric part. As stated in our previous blog post: dynamic exercises are any exercises that requires or involves joint movement. When we're doing dynamic exercises it is important to work through the full range of motion. And this is where we start to answer the question asked by our #teamfitbest member! By working through the full range of motion, also commonly known as ROM (accepting that you don't have any physical or medical conditions preventing you to do so): the whole length of the muscle is stimulated. This will lead to muscle tears (the good ones remember) in the entire muscle group which you are working and not only in certain parts of it. You will VERY often hear us say - "remember it's not about the speed of the movement, it's about the control of the movement." There are millions more benefits of going a little slower on the reps and ensuring that you work through the entire ROM. Cracking out jumping lunges whilst looking like one of those inflatable advertising mans has little to no health benefits. The only benefit is that it will ref up your heart rate - but from a strength and conditioning perspective...😑 You would have gained more in the same amount of time by doing slow alternating reverse lunges, working through the entire ROM. I am not saying jumping lunges are bad for you. Please no! They are terrible to do, but great for your lower body muscles. However, if you haven't been training for 6 months + I would not recommend incorporating jumping lunges or jump squats into your workout routines. It's important to master the basics first before you take it up a notch! Moving from lunges to jumping lunges or squats to jump squats are simply different variations, working on different types of muscle fibres! Now this is where my geek-biology loving excitement comes in! So back to the question we got: "What are the pro's and cons of dynamic vs static exercises? Dynamic being squat jumps, mountain climbers and static being slow moving resistance band exercises, bench press, squat etc." Our muscles consist of fibres as we have established in the previous blog post. But did you know that your muscles consist of different types of muscle fibres??? Every muscle in your body consists of a combination of Slow Twitch / Type 1 & Fast Twitch / Type 2 muscle fibres. Slow twitch (Type 1) muscle fibres are used for endurance exercises. Slow twitch muscle fibres fatigue slower but are less powerful. Whereas fast twitch (Type 2) muscle fibres are used for short, fast movements such as sprinting or jumping. Fast twitch muscle fibres fatigue faster but are more powerful. Thus the question was rather about the muscle fibres that works to perform these exercises listed above. Exercises such as sprinting, jumping lunges, jump squats or mountain climbers will activate your fast twitch muscle fibres. These exercises usually doesn't last for a long period of time and can feel the physical fatigue of your muscles quite fast. Exercises such as long distance running, slow moving resistance band exercises or bench press, weighted squats, etc will activate your slow twitch muscle fibres. These exercises usually last longer and it will take longer for your muscles to reach fatigue. Now you might ask, so which is best? The answer is: Both! Depending what your fitness goals are will determine which muscle fibres you want to put to work during your workouts. Like we said, when you workout your muscles tear. Depending on the type of workout you're doing will determine which type of muscle fibres will form. Say for instance you are a long distance runner. You would therefore rather go for exercises that includes slow twitch muscles. You would for instance rather opt for walking lunges instead of jumping lunges. You want to work through the full ROM, strengthening your endurance ability of your muscles. You definitely might include jumping lunges or jump squats or box jumps, etc in your training sessions. But most of your workouts would focus on building muscle endurance. There would be little to no benefit for a long distance runner to build type 2 (fast twitch) fibres when training. For the record long distance speed work is still training for type 1 muscles. The opposite would be true for sprinters. Sprinters would focus mainly on activating and strengthening type 2 (fast twitch muscles). Plyometric exercises such as jumping lunges, jump squats, tuck jumps, box jumps, etc as well as agility exercises would be excellent for them. As they would want to build more fast twitch fibres - to provide their muscles with explosive and agile strength to perform for a short period of time. If you want to do weight lifting to build lean muscle and strength - the major muscle fibres you would want to create - are type 1 (slow twitch) fibres. Being able to perform a few reps consecutively with a certain amount of weight. If power lifting is your aim - the type 2 (fast twitch) muscles will be trained more. As you want to get the maximal output / force from your muscles for 1 or 2 reps max. So to summaries: Type 1: Slow Twitch = Optimal Performance for an extended period of time. Type 2: Fast Twitch = Optimal Performance for a short period of time. Both muscle fibres will work when you train. But the type of exercise you perform when training, will determine which type of muscle fibres would form. Selecting the correct exercises is vital in reaching your fitness goals. Ever wondered why men can lift weights but most of the time look like their gonna faint when doing a class with their wives or girlfriends? Now you understand! Most men perform weight training exercises which mostly activates the building of slow twitch muscle fibres. Whereas women (the average women who joins group fitness classes - who does not train sport specific), perform exercises that vary in which type of muscle fibres are required. Women's bodies in general are more balanced between slow and fast twitch muscle fibres. And thus, we get to have a little fun and feel like total bad asses when our husbands and boyfriends train with us and appear to be close to death. Next time, just pass them your sweat towel and tell them to women up a little!

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