Motor Learning and Muscle Physiology Concepts with Bas Van Hooren

Bas Van Hooren is an athlete, applied sport scientist, and strength and conditioning specialist from Gronsveld, The Netherlands. He currently lectures at Fontys University of Applied Sports Sciences. As an athlete, Bas has won multiple medals at the national championships, including a gold medal at the national championship 3000m indoor in 2017.

As an applied sport scientist, Bas has written multiple peer-reviewed scientific publications about a variety of sport science topics, and has a special interest in the transfer effects of training on sports performance and injury prevention. Bas has trained individuals ranging from the elite to recreational levels with a special interest in sports that involve running. He has a bachelor’s degree in applied sport sciences from Fontys University and a master’s in Human Movement Sciences from Maastricht University.

Freelap USA: What is your take on the role of variability in training?

Bas Van Hooren: Variability in training is important for several reasons. First, we obviously need to use some variability to avoid monotonous loading of the same tissues, which may lead to injuries when repeated over a longer time period. Further, according to the law of diminishing returns, the effectiveness of training will decrease when we repeat the same stimulus multiple times because our body will adapt and therefore be better prepared for this stimulus. For example, when we introduce a new exercise such as a power clean into our training program, we will initially progress quite fast, but progress will slow down over time. Therefore, we need to apply progressive overload by increasing the load or number of reps and sets, or we can use variations of an exercise.

Variability may also be useful from a motor learning perspective. The traditional idea in motor learning is that there is one ideal movement pattern that is similar for everyone. This ideal pattern must therefore be practiced over and over again to optimally learn this pattern. However, several studies have found that recreational and even elite athletes use slightly varying movement patterns, showing that one ideal movement pattern that is similar for everyone likely does not exist. Other studies have shown that a movement pattern is not even similar within the same individual across different days, during a single day, or even during a training session.

Since each individual is slightly different and because the same individual changes slightly over time (for example, due to fatigue, maturation, or aging), these different movement patterns likely reflect an attempt to perform a stable and efficient movement within the constantly changing body (and changing environment, when applicable). Variability in movement is therefore a must rather than an optional requirement.

Variability in movement is therefore a must rather than an optional requirement, says @BasVanHooren. Share on X

Introducing extra variability in training may assist the body in finding the movement pattern that best matches the individual. Numerous studies have indeed shown that more variability can lead to better learning of motor skills than repeating the same skill over and over. This variability approach to motor learning is known as differential learning. It should be noted, however, that there is an optimum amount of variability. Introducing even more variability and variations beyond this point will not improve performance and may actually negatively impact performance by inducing extra fatigue.

Freelap USA: How should we look at the role of the biarticular muscles and muscular timing in the scope of coordination training?

Bas Van Hooren: Biarticular muscles have an important role in transferring energy during high-intensity movements such as running, jumping, and throwing. For example, in vertical jumping, the biarticular gastrocnemius muscles will transfer energy from knee extension into plantar flexion of the ankle joint. This will, however, only happen when they remain near isometrical and therefore essentially act as a rope at the right time during the movement.

Computer modelling studies have shown that even minor errors during the time when muscles are activated and deactivated can cause major deteriorations in performance because the energy transfer is suboptimal. For example, a decrease of 10 centimeters has been observed with vertical jumping! In humans, this error is smaller (~2 cm) than in computer models, but it can still make the difference between winning or not winning a medal or potentially getting an injury or not getting an injury, especially for elite athletes.

Performance may drop when a muscle’s strength improves without improving intermuscular coordination, says @BasVanHooren. Share on X

Training for intermuscular coordination (training how muscles optimally cooperate with one another) is therefore important to maximize performance, especially after a period of rehabilitation during which some muscles or muscle groups may have been trained in isolation. Indeed, both computer modelling studies and experimental studies in humans have shown that performance may actually decrease when the strength of a muscle (group) is improved without improving the intermuscular coordination. Therefore, in addition to muscle strengthening, optimizing intermuscular coordination is also important.

Freelap USA: With coordination training, how much of training (outside of actual sport practice) should be in a mode where we challenge coordination, versus overloading an athlete via intensity (such as common barbell overload means)? Are there situations where one mode or the other may be preferred?

Bas Van Hooren: Unfortunately, it is impossible to say that, for example, 60% of training should be focused on training intermuscular coordination and 40% on improving intramuscular coordination and other structural adaptations, and thereby muscular strength. The first reason is that it is difficult to classify training as coordination-only or overload-only.

For example, when we perform a heavy back squat, we might improve muscular strength via structural adaptations such as a larger muscle cross-sectional area, a stiffer tendon, and higher motor unit recruitment. However, we might also improve the intermuscular coordination between muscles such as the gluteus maximus, rectus femoris, and gastrocnemius if we perform the concentric phase as fast as possible.

Similarly, when we perform a high-intensity sprint, we need a very precise timing of the gluteus maximus, rectus femoris, and gastrocnemius activity during the push-off and therefore, this likely trains intermuscular coordination. However, we likely also improve muscular strength by inducing structural adaptations and intramuscular coordination such as a higher firing frequency.

So, it is difficult to classify training as either coordination or strength training because almost all training will target both adaptations, at least to some degree. Nevertheless, most people will agree that some exercises are probably more suited to train intermuscular coordination and some exercises more suited to train muscular strength.

It’s hard to classify training as coordination- or overload-only or recommend how much of each mode, says @BasVanHooren. Share on X

However, even when we try to classify exercises as predominantly coordination or muscular strength training, it is difficult to recommend how much of each mode should be performed because the distribution of these training modes likely differs between sports and between individual athletes. For example, in some sports intermuscular coordination may be of less relevance because the sport is being performed under less time pressure (e.g., powerlifting), while in other sports intermuscular coordination may become very important (e.g., maximum velocity sprinting).

Additionally, athletes who have performed a large amount of isolated strength training, for example in pre-season or rehabilitation, may benefit from more coordination-focused training to transfer these strength gains into performance gains. Some (periodization) studies reported that there was some time needed before strength gains in the weight room transferred into improvements in sports performance. The improvements in performance might have been made sooner if more coordination training was incorporated.

On the other hand, individuals who have been performing mostly coordination-focused training without much quantitative overload (e.g., distance runners that have performed mostly distance running, some high-intensity running, and specific running exercises like A-skips) may benefit from doing some more training that improves their muscular strength.

Freelap USA: How important is the consideration of muscle fascicle length in training and what are some ways coaches can approach this in terms of training implications?

Bas Van Hooren: Fascicle lengths have been related to injuries and performance. For example, individuals with shorter hamstring fascicles and lower strength have been found to be at a higher risk of hamstring injuries. Other studies have found faster sprinters in running and swimming to have (slightly) longer muscle fascicles, which suggests that the higher shortening speed of longer fascicles may be beneficial for faster force production. Both these findings suggest that longer fascicles may be beneficial in some situations.

There are conflicting findings about the effects of training on fascicle length. For example, although eccentric muscle actions are most likely to induce increases in fascicle length, fascicle length has also been found to increase following concentric and isometric training. Therefore, fascicle length changes may not only be a consequence of the muscle contraction mode, but also of other factors such as the length and velocity at which the muscle is trained, with longer lengths and higher velocities potentially leading to longer fascicles.

Coaches could therefore attempt to increase hamstrings’ fascicle lengths by using eccentric exercises such as the Nordic hamstring curl and calf muscle fascicle length by using an eccentric-only calf raise. However, the potential disadvantages of such exercises in terms of muscle soreness and lack of intermuscular coordination training should also be considered.

Freelap USA: How does the stiffness or compliance of human tendons impact speed and power? How do various training modalities impact this stiffness, particularly resistance training?

Bas Van Hooren: When a relaxed muscle contracts, it does not immediately result in movement of the joints, and thus body movement, because slack first has to be taken out of the muscle and the tendon has to be stiffened. These processes are comparable to pulling a car with an elastic rope.

First, slack needs to be taken out of the rope. When the slack is taken out, the rope will be further stretched until the force required to stretch the rope is higher than the force needed to move the car. Only at this point will the car start to move. The elastic cable can also recoil, hereby further pulling the car forward.

Something similar happens when the muscle contracts from a relaxed position. First, slack needs to be taken out, the tendon will be stretched until the force required to stretch the tendon is higher than the force needed to move the joint. Only at this point will the joint start moving. The tendon can also recoil, which can result in further joint movement. The whole process of taking out slack and tendon compliance can take up to 100 milliseconds from a relaxed position. Since the time available to produce force is limited in many sport situations, these processes can therefore limit performance.

Large amounts of #plyometric training may cause an imbalance in muscle strength and tendon stiffness, says @BasVanHooren. Share on X

A large body of research has investigated the effects of training on tendon stiffness. A meta-analysis by Bohm and colleagues (2015) showed that only heavy loads (>70% 1RM) are effective at improving tendon stiffness, while lighter loads (<70% 1RM) are generally ineffective. These findings confirmed previous research that showed tendon tissue to be most responsive to high loads applied for a relatively longer duration of about three seconds, rather than very short loading durations as in plyometric training.

However, other studies have also shown improvements in tendon stiffness with plyometric training, but these adaptations may simply take longer to manifest. Therefore, there can potentially be an imbalance in muscle strength and tendon stiffness due to large amounts of plyometric training, which may lead to tendinopathy injuries.

Research

Bohm S., Mersmann F. & Arampatzis A. “Human tendon adaptation in response to mechanical loading: A systematic review and meta-analysis of exercise intervention studies on healthy adults.” Sports Medicine – Open. 2015; 1(1): 7.

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