Why Strength Endurance and Conditioning Are Crucial for Performance

By on November 25, 2021

Being extremely strong is very useful but, right now, there is a massive trend toward praising strength above all other aspects of fitness. I’ve even heard the claim that if you train max strength, you don’t need to train for strength endurance. I strongly disagree. In fact, I’d go as far as to say that if anything is foundational for performance, it should be strength endurance, moreso.

Strength Endurance Battle Ropes

Strength endurance is simply the ability to continue exerting force for a significant amount of time. Lifting 150kg on the bench press once is a great demonstration of max strength. Lifting 100kg for 10 reps is a good demonstration of strength endurance.

Very rarely in life, or in sports, are we asked to lift something extremely heavy once and then put it back down. Far more often, we are required to lift something very heavy and carry it. Or to perform a simply action against resistance repeatedly. Martial arts, rowing, rock climbing, moving furniture, construction, carrying luggage, carrying children… all these things require strength endurance rather than max strength.

Very rarely are we asked to lift something extremely heavy once and then put it back down.

So, why do some people claim that max strength somehow “trumps” strength endurance?

Max Strength vs Strength Endurance

The argument goes that if you task two people with bench pressing 100kg 10 times, the person with the bigger max bench will perform better. The reason for this, of course, is that the stronger individual is pressing a smaller relative fraction of what they are capable of – thus making that movement less fatiguing.

This argument breaks down, though, as soon as we ask those same two people to perform battle ropes for 10 minutes. Or to hit a punch bag for ten minutes. The latter example is using many of the same muscles, albeit not precisely, but the strength athlete will lose their advantage.

Likewise, if you lower the weight to just the bar and see who can press it for the longest, that strength will lose its usefulness.

Benching

The reason for this, is that strength endurance actually is determined by multiple factors. One reason the bench presser can press more is simply that they have become more efficient at that movement. They are readily able to recruit more motor units and they can perform the exercise without energy leaks. The noob will find their arms wobbling around as they struggle to execute the pattern correctly. Learning to bench press won’t help them to punch harder, for longer.

More Reasons to Train for Strength Endurance

Moreover, there are localized adaptations that improve the endurance of those muscles specifically. For example, you will increase blood supply to the muscles via angiogenesis, alter the types of twitch muscle fibers available.

See also: Rethinking Endurance – Specific Peripheral Adaptations

Bench pressing your max will help you to build more type IIa muscle fibers, which means you’ll have more to work through before they all become fatigued. However, type II fiber is also less energy efficient, which is why this advantage is lost once you lower the weight enough and increase the amount of reps. Because, conversely, a less power-oriented athlete will have a greater pool of slow twitch fibers.

Car Pushing

What’s more, is that you also need the systemic work capacity (central endurance) to match that continuous power output. Training the muscles this way requires a lot of oxygen and so you’ll need a good cardio base to continue past the lactate threshold. And the heavier you are, the better your oxygen turnover and stroke volume need to be.

Training With Light Weights Makes Sense

So, in short, you can’t achieve optimal strength endurance with extremely heavy weights. You also need to lower the weight and add more volume, so as to train the slow twitch fibers, get better at handling a build-up of metabolic waste products, increase glycogen stores, etc.

Training the slow twitch fibers, though, is something that many of us intuitively avoid. We avoid it because slow twitch fiber is smaller and weaker. So why would we want it, right?

See also: The Surprising Benefits of Using Partials (Range of Motion)

Well, as Pavel Tsatsouline points out, slow twitch fibers, though weaker, are actually just as strong per square inch of cross section. In other words, loads of slow twitch fibers are as strong as a few fast-twitch fibers and take up just the same amount of space.

A study Pavel references, by Selouyanov, found that experienced athletes could increase their 1RM on the squat by training with light weights and a slow cadence.

A quote from Selouyanov stated:

“[Although] maximal speed of ST and FT muscle fibers differs by 20-40%, the contraction speed in real athletic actions does not exceed 50% of the maximal contraction speed.  Thus, an increase in strength of the ST fibers increases power and speed practically in all types of athletic activity.  Even in a sprint.”

Selouyanov

We should also note that fast twitch fibers produce the most lactate, which can lead to muscle burn and fatigue.

How to Train Your Slow Twitch Fibers

So, training your slow twitch fibers will increase both muscular endurance and power. And to train this way, you need to lighten the weight and perform very slow repetitions. This, in accordance with Henneman’s Size Principle, will prevent the fast twitch fibers from taking over, and will allow you to continue training past the point where those larger motor units would normally become fatigued. This gives you the chance to properly simulate the slower twitch fibers, as well.

Battle Ropes Jump

You could achieve something similar with isometric training. Isometric training involves holding a position under resistance. In an extreme isometric, you might do this for several minutes until your whole body begins shaking. At this point, you have fatigued your slow twitch muscle fibers and have moved to faster twitch fibers and larger motor units. The shaking is a clue that this is happening: you shake because you’re now contracting larger fibers that cause movement!

The Drop Set

The danger, is that in a bid to utilize all available muscle fibers, you keep rest periods to a minimum. In so doing, you might be able to hit the muscles again before all fibers have fully recovered. In theory, this could result in greater total activation of the muscle. However, this might also mean that you are still suffering from “central fatigue.” If your nervous system hasn’t had time to fully recover, you might find you are not as able to recruit all the necessary muscle fibers, or to train to your fullest ability.

(I do think this is a worthy tradeoff, often. However, it is a concern among those focused on strength and size alone.)

Tired Outside

The solution that I always promote is the drop set. Here, you train by using a heavy load that will work the fastest twitch fibers, and you go to failure. From there, you switch immediately to training the same movement with a lighter load – allowing you to work those smaller twitch fibers. You repeat this process as many times as you wish, potentially fatiguing all available muscle fibers. This also works to a slightly lesser degree with a “mechanical dropset.” Here, you keep the weight the same, but alter the biomechanics so as to make the movement easier. For example, this could mean performing as many push ups as possible, then switching to push ups on your knees

Another option is to end a very heavy set with a long isometric hold to failure, or a “flush set.”

Isometric Squat

Going to Failure, Safely

Note that when training to failure, or training while fatigued, it is advisable to stick with safe movements with low risk of injury. That might mean closed-chain bodyweight movements (like push ups), or it might using resistance machines. You can do some crazy stuff using a chest press with extremely minimal risk of injury.

You can now hit every muscle fiber in a way that provides max strength AND work capacity/strength endurance. At the same time though, you can use sufficient rest periods in order to fully recover before round two – achieving not just volume, but high quality volume.

The Role of Glycogen

For longer rep-ranges, weightlifting will rely on the glycogen-lactic acid energy system. Here, glycogen is broken down into pyruvate, which is then further metabolized into ATP. Should there be enough available oxygen, pyruvate can be completely oxidized via the tricarboxylic acid (TCA) cycle into even larger amounts of ATP.

It’s not entirely clear whether focussing on a more bodybuilding-style form of training will increase glycogen storage significantly over strength-focussed training. Any difference is likely to be negligible.

However, bodybuilders likely enjoy greater work capacity simply because they chose to focus on size.

Side view battle ropes

Specifically, adding five pounds of muscle will let you store 75-100g more glycogen, meaning that you can train at higher intensity for longer, before switching to your aerobic energy system (which necessarily forces you to use slow twitch fiber).

See also: Learning From Legends – Arnold Schwarzenegger

So, it’s not necessarily that “sarcoplasmic” hypertrophy uses a special mechanism to increase glycogen storage. Rather, it’s that bodybuilder-style training focusses on size, and more size naturally equates to more glycogen. And bodybuilders achieve that size through large total training volume, and a focus on metabolic stress and muscle damage.

What is very interesting, is that recent research suggests glycogen availability to act as a potent signal. In short, when glycogen supply is low, mitochondria production gets ramped up. This works by activating AMPK, which will suppress hypertrophy but upregulate mitochondrial biogenesis (reference, study). Though this same process would also downregulate protein synthesis.

What Causes Fatigue?

It is also the process of glycolysis that leads to the creation of metabolic waste products, such as lactate and hydrogen (although there is evidence that all energy systems create lactate). Lactate can actually be used for additional fuel and is not the enemy it was previously thought of as. Lactate is shuttled to areas where more oxygen is available – such as the heart, liver, and brain – and is there oxygenated back into glucose. From here, it can be shipped back to the muscles! When these systems are working correctly, they actually aid with the smart distribution of energy throughout the body – ensuring that the energy is provided where it is most needed.

Others have pointed to hydrogen ions as the waste product we need to worry about. Hydrogen ion build-up is thought to inhibit anaerobic ATP production, which interferes with muscle contraction and increases blood acidity (reference). (By interfering with calcium release from the sarcoplasmic reticulum, among other things.)

With that said, there is also evidence to contradict this theory, and there are many other factors that may be responsible for muscle fatigue (reference). Such as ionic changes to the excitation contraction coupling. Fascinatingly, we don’t really know what causes muscle fatigue! This shows just how under-explored this area of performance really is!

Isometric Squat

Better Circulation

What we do know, is that, in general, the body’s ability to ferry waste products away from the muscles can reduce peripheral fatigue. Circulation to and from the muscle can play a large role in improving work capacity, therefore.

And to train this, we simply need to challenge these systems. That means: reducing the rest between training, and increasing the rep range. This is the SAID Principle: specific adaptations to imposed demands.

Shorter rest periods may mean you lift less and gain strength more slowly. But the reality is that this is going to train you for sports and the real world – where sitting out for 3+ minutes is not always an option!

Alternatively, you can stay active during rest periods in order to keep the aerobic system working and keep blood moving around the body.

Blood Flow Restriction

Note that many of these adaptations are localized. In other words, endurance will improve specifically in the muscles that are being trained that way. Someone who is very good at long distance swimming, therefore, may not naturally be good at long-distance running.

So, a martial artist who wants to improve their work capacity for sparring might do well to train the same muscles in the ways we have discussed. They might do this with very high repetition resistance band punch outs, for example.

Endurance Training

We can also improve overall endurance, and thus work capacity. This will help to reduce central fatigue, and ensure that our energy systems are working optimally to support our effort. This will increase VO2 max, stroke volume, vascularization and more.

If you’re wondering why bodybuilders with big muscles – and thus big stores of glycogen – typically don’t make great endurance athletes… this is why! Muscle is expensive from an energy standpoint (and heavy!). The more muscle you have, the bigger “engine” you need to power it.

Running

Simply adding a couple of cardio sessions per week (or even just one) can make a big difference. Weightlifting is far more metabolically demanding than most people realise, and you should find that this is apparent when you build a bigger engine.

If you’re concerned about running because you think it will harm your gains, know that you’re losing a lot more in the long run! Even if your growth comes a little slower, you’ll ultimately be able to express that strength for longer, in real-world settings. Not only that but, over time, you’ll find that you recover quicker, train harder, and get more high-quality volume. Simply because you have more energy during your workouts!

See also: Why Everyone Should Run (Like Bruce Lee)

Finishers for Muscle Endurance

Alternatively, we can add finishers to the ends of workouts – at the point where they won’t negatively impact the quality of the training. This has the added benefits of targeting more and different muscle fibers in the areas you’ve just worked (if you select appropriate finishers). It also means you get to keep the tension on the muscles longer, thereby encouraging more metabolic stress – and potentially more hypertrophy. And longer training sessions will improve the body’s ability to regulate heat by shunting more blood to the surface. 

If you don’t like the idea of running a couple of times per week, you might find that adding battle ropes or med ball slams to the ends of workouts is more palatable!

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About Adam Sinicki

Adam Sinicki, AKA The Bioneer, is a writer, personal trainer, author, entrepreneur, and web developer. I've been writing about health, psychology, and fitness for the past 10+ years and have a fascination with the limits of human performance. When I'm not running my online businesses or training, I love sandwiches, computer games, comics, and hanging out with my family.

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