Previously it was thought a muscle almost certainly couldn’t be worked differently along the direction its fibers run. However, a recent study by Bret Contreras and Brad Schoenfeld from the Journal of Strength and Conditioning Research cast more light on this often misunderstood aspect of training.

Study Design

There were ten participants, all well trained in resistance exercise. They had about 4.5 years of experience on average, and their average stiff-legged deadlift (SLDL) was about 300lbs, which is pretty decent. For the study, they each performed both an SLDL and a lying leg curl. Half of the subjects performed one exercise first and the other half did the other first. They used their eight-rep-max for the test and performed as many reps as they could with a fixed cadence.

During the tests, the participants were hooked up to electrodes to take EMG readings and measure muscle activity. Four regions of the hamstrings were selected, two on the upper hamstrings, near the glutes, and two on the lower hamstrings, closer to the knee. On both the upper and lower portions, one electrode was on the inside part of the leg and the other was on the outside at the same level.

Results

The results may come as a surprise. In general, the leg curl yielded the strongest response in the hamstrings. The SLDL was stronger only in the upper-inside EMG results and only by an insignificant margin.

Of particular interest was that the upper and lower parts of the hamstrings had substantially different responses to each exercise. Specifically, the researchers found it was possible to emphasize an upper or lower part of the hamstring depending on the exercise.

Now that may be blasphemy for some coaches, but it’s not as crazy as it sounds. While the results are useful for muscle building, and particularly for the superficial muscles, they aren’t absolute, stand-alone evidence that muscle fibers can be preferentially recruited along their length. This is because the EMG readings were for portions of muscle and included readings from several muscle heads simultaneously in some cases.

For example, part of the reason for the elevated response shown in the leg curl was because of the activity in the short head of the biceps femoris. This muscle only activates significantly during knee flexion.

Still, this doesn’t fully explain why the medial electrodes picked up stronger signals near the origin of the muscle compared to near the knee. It could be because each of the heads of the hamstring has an attachment on the medial side of the back leg, and thus the EMG data reflected the work of a larger portion of the hamstring.

Conclusions

We can say two important things based on this data. First, for people working to build muscle for aesthetic reasons, regions of the leg can be preferentially selected, even from top to bottom. The results suggest regional muscle development does seem to be possible.

Second, and more important, working biarticular muscles like the hamstrings in a variety of ways is important. If a muscle crosses multiple joints (e.g. the biceps, triceps, hamstrings, quads, and calves), spend time working all the functions of the muscle for complete strength development.

References:

1. Brad Schoenfeld, et. al., “Regional Differences in Muscle Activation During Hamstrings Exercise,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.00000000000005

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I want to shed some light about different body types, why some people can lift more weight than others, and how some people are more inclined to endurance work then others. Everyone is keen to a body type, but it’s important to program and work with your genetic musculature to make strength gains. Hopefully, reading about overall body type will help you see what your particular body type is, and help you reach your full potential.

Slow Twitch Muscle Fibers

(AKA: Slow Oxidative or Type I Muscle Fibers)

Athletes with this type of muscle tissue will usually be much leaner. Their muscles look visibly longer, and they usually have little body fat. There is a reason why their bodies look this way. Type I muscle fibers contain large amounts of mitochondria. Going back to cell biology, mitochondria are the powerhouses of the cells. Increased mitochondria means more ATP production (energy).

The full name for ATP is adenosine triphosphate, and it is a molecule involved in energy transfer and production. ATP is vital to all cells in the body, but in skeletal tissue it is an important aspect of the sliding filament theory, or simply put, how our muscles contract.

Type I muscle fibers are surrounded by more capillaries, which means muscles get more blood flow and transfer, and contain higher concentrations of myoglobin (pictured right). You may be wondering, what the hell is myoglobin? Myoglobin binds to oxygen and acts as a muscle reservoir for oxygen when the blood does not supply an adequate amount, so you can think of it as a storage center for oxygen. All of these factors summed up together make type I muscle fibers extremely resistant to fatigue, and capable for sustained aerobic metabolism.

Something that is important to mention here is that type I muscle fibers contract more slowly. These muscles create a lower force output and are more efficient during long duration workouts than their fast twitch counterparts. You may have recognized the oxidation part in the name of slow twitch muscle fibers. These muscle fibers perform under aerobic conditions, so oxidation means that oxygen is required for aerobic respiration to generate ATP. This has a lot to do with heart rate, the range at which aerobic respiration is taking place, and when anaerobic respiration is taking place. So, people with this muscle type usually can’t lift as much weight, but they do well during long durations and muscular endurance.

People in this group type can still lift heavy, but how they train is key. It is important for people in this group to have an efficient warm up to get to an aerobic state to generate the max amount of force for muscle contraction, thus lifting a heavier load. Also, type I muscle works best when workouts are over three minutes long, so higher reps usually do better for building strength for the type I group. So instead of doing a lot of 1 rep maxes, try doing 7, 5, and 3 reps (heavy) for so many sets and shorter rest, and save your 1 rep maxes for personal record attempt days.

Lastly, time under tension is important for this group to make strength gains. Moving slower in movements will help make improvements in lifts over time so you can lift more than the athlete next to you.

Fast Twitch Muscle Fibers

This group has two subtypes. Understand that all fast twitch muscle fibers bear certain traits. All fast twitch muscles have high concentrations of glycogen (from which glucose is derived), and something all of you may find interesting, is that most fast twitch muscle fibers appear white. Most people who fit into this category will have a bigger skeletal and muscular structure and the appearance of larger muscles.

Fast Twitch Muscle Fibers: Type IIx

This subtype classification is relatively new in that it was categorized in 1980. This subtype of fast twitch muscle fibers contains small amounts of mitochondria, which means these muscles do not do as well during long duration workouts. These muscles have a small capacity for aerobic metabolism, and fatigue more easily than their slow twitch counterparts. These fibers can’t sustain their effort for more than a few seconds.

It may sound like these type of muscles are just awful, but here are the benefits of this type of muscle tissue. These muscles posses a higher number of glycolytic enzymes. What does this mean? It means these muscles perform anaerobically; so they do not need oxygen to produce ATP. With these characteristics, these muscles have the ability to produce a lot of force (lifting), but in short durations. Ultimately, these muscles are tailor-made for lifting in that they do well with short, explosive movements. But when it comes to metabolic conditioning or a long duration CrossFit WOD like “Eva,” people in this category work much harder to sustain and keep their muscles from fatigue. Endurance is something people in this category need to work on.

Fast Twitch Muscle Fibers: Type IIa

AKA: “Intermediate” or Fast-Oxidative Glycolytic Fibers (Whew!)

This subtype has the same characteristics as mentioned above with a few differences. These muscles possess properties of speed, fatigue, and force production somewhere between type I and IIx fibers, therefore they can work up to three minutes in elite athletes. People in this category are highly adaptable. They are able to increase their oxidative capacity to levels similar to that of the slow twitch group, but at a cost. When people in this subtype go into the oxidative capacity, they tend to lose more muscle mass, therefore, losing some of the strength portion of their overall fitness.

In the human body, the composition is typically equal number type I fibers and fast twitch fibers, though some muscle groups are made up of primarily of type I, or predominantly fast twitch in the skeletal muscle (for example, looking at the legs it can be very obvious what type of muscle tissue you have). This can be attributed to genetics, hormones, and activity of the individual.

Remember, this is only one variable that determines success in the CrossFit realm of lifting and overall physical performance. For the type I group of athletes, you may have to adjust how you do your lifting days in comparison to the fast twitch group to make strength gains, but you can lift as much as the CrossFitter next to you if you train correctly.

Photos courtesy of Shutterstock.

The post The CrossFit Dilemma: Why Can’t I Lift More Than THAT Person? appeared first on Breaking Muscle.

Broscience is everywhere in the training world. Broscience, as defined in the urban dictionary, is “the predominant brand of reasoning in bodybuilding circles where the anecdotal reports of jacked dudes are considered more credible than scientific research.”

Scientists are more concerned with how things really are. They carefully design and painstakingly execute studies to find out what is really going on in our bodies when we train. They argue over the meaning of the results. They review each other’s work, and, when enough of them agree, the findings are published. That is how the Henneman size principle came to be. The Henneman size principle states that motor units are recruited in an orderly manner from smallest to largest, and that recruitment is dependent on the effort of the activity.

Unfortunately, how that information is used cannot be controlled. The widespread misapplication of the Henneman size principle, leading to the popular but unsupported belief that heavier-is-better for strength training, is an excellent example of broscience picking up where the research left off.

An important premise in strength training is that a motor unit (what muscles consist of) can only strengthen and grow when used. Hearing this, your bro, who knows all about the Henneman size principle, tells you that if you want to get stronger, you should pick up really heavy things. This faulty inference has led to claims that the Henneman size principle supports the 3-5 repetition maximum training intensity for greatest strength gain.

Some definitions:

• Force – a weight or pressure. Examples are: a barbell and pushing against the barbell
• Effort – how hard you are trying to develop force with your muscle
• Intensity – expressed a maximum number of repetitions or a percentage of the one-rep max, how difficult a given force is to resist
• Motor Unit – a group of muscle fiber bundles all attached to the same neuron

A simple way to illustrate how force and effort differ is with a single dumbbell. Let’s say it’s a 40lb dumbbell, and I ask you to perform an isometric hold at the halfway point in a dumbbell curl. It doesn’t matter how long you hold it, it will continue to weigh 40 lbs. The force you are producing is a steady 40lbs (for a while, anyway.)

The effort you are putting into holding it there, however, will clearly increase over time. I can tell by the look on your face. At some point, the external force (which hasn’t changed) will overcome your effort, and you will lower the dumbbell. All the muscle fibers involved in flexing your elbow have failed. Would this experiment look any different if I handed you a 20lb or an 80lb dumbbell? No, with the likely exception of how long you could hold it. Otherwise, it would play out the same way.

Effort results from electrical stimulation of motor units (i.e. a decision to apply effort and generate force) and not the externally applied force. Interpolated Twitch Technique (ITT) is a way to measure muscle activation by applying an electrical current to a muscle already under Maximal Voluntary Contraction (MVC.) If any additional force is detected upon applying the supramaximal electrical stimulus, then it is concluded that the MVC was not a true maximal contraction. In other words, the muscle still had some strength left to give that the owner could not voluntarily elicit.

Scientists asked groups of old and young men to exercise at specific intensities and with specific time-under-tension. When they compared muscle activation and force development using ITT, what they discovered confirmed that the intensity of effort, not the external load, determines force output. No matter the intensity (5RM, 10RM, or 20RM) and time under tension (35, 70, and 140 seconds, respectively), no significant differences in motor unit activation occurred. Greater resistance did not have any effect on muscular activation. Their conclusion, verbatim: “the commonly repeated suggestion that maximal strength methods [resistance heavier than 6RM] produce greater neural adaptations or increases in neural drive was not substantiated in this study.”

The take-home message is this: motor unit recruitment depends on stimulus from the brain, not application of weight. It is absurd to cite the Henneman size principle when making repetition range prescriptions for strength or hypertrophy goals. So why is it done?

The strange truth is that, for all we know, 3-5 reps @85% of 1RM might be the prescription for fastest and/or greatest strength gain, but it might not be. The experiments done regarding the Henneman size principle have been widely misinterpreted, and the bulk of textbooks on the subject use this erroneous interpretation. Assuming that our original premise, that a motor unit grows and strengthens when used, is true, and that motor units fire from smallest to biggest as effort, not external force, increases, any weight that can elicit momentary failure should be effective for increasing strength.

At first blush, this seems like madness. Then again, consider the common term “farmer strong.” Hand-loading 600 bales of hay makes a person strong, but if each bale is only 70lbs and the farmer can deadlift 400lbs (intensity=17.5% 1RM), how is that possible? Consider the highly effective Wendler 5/3/1 strength training system. The first two work sets of the day are essentially heavy warmup sets followed by one work set to failure (fire every motor unit, use the entire muscle). Consider gymnasts and others using bodyweight as their only resistance. These people become extremely strong, often without any regard, or even knowledge, of the relative intensity of each repetition.

Knowing what you know now, go back and read the books that you taught you what you “know” about strength programming. New questions come up.

References:

1. Ralph N. Carpinelli, “The Size Principle and a Critical Analysis of the Unsubstantiated Heavier-Is-Better Recommendation for Resistance Training,” Journal of Exercise Science & Fitness 2008, 6:2.

Photos courtesy of Shutterstock.

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