Should we ever program heavy strength training for sprinting?
Not that many years ago, sprint coaches were unhappy about their athletes using heavy strength training, because they thought it would make them slower. Over the last few decades, that perception has reversed.
These days, it seems that most sprint coaches encourage their athletes to perform heavy strength training, at least for part of the year. Indeed, many athletes who sprint use a block periodization approach to strength training, using periods of heavy strength training followed by periods of high-velocity power training, or sports-specific exercises.
Even so, there are good reasons to believe that heavy strength training does decrease maximum speed in athletes, and may therefore be unhelpful for sprinters.
So is heavy strength training useful or not?
How do muscles produce force during sprinting?
Although sprinting is a high-velocity movement, this does not mean that all of the lower body muscles are shortening quickly, all of the time.
This is very important, because it is the shortening speed of the muscle that determines whether high-velocity strength and maximum speed are valuable, not the speed of the movement itself.
Hopefully, it goes without saying that the transferable strength gains that result from training involve adaptations to individual muscles. Although strength gains in an exercise do occur as a result of coordination, these do not transfer from the exercise to the sprinting movement. Therefore, we need to focus on what the muscles are actually doing while we are running.
Moreover, we need to be aware that each of the lower body muscles contributes differently to the sprinting movement. Some contribute to a greater extent than others, and in different parts of the gait cycle.
We can understand better how each of the lower body muscles contributes to sprint running from studies that have performed biomechanical analyses of the joints and muscles during running at various constant speeds, including maximal speed sprinting.
Such studies show us that the hip extensors (gluteus maximus, adductor magnus, and hamstrings) and hip flexors (iliopsoas and rectus femoris) contribute most to lower body power generated and positive work done in the swing phase, while the knee extensors (quadriceps) and knee flexors (hamstrings) contribute most to lower body power absorbed and negative work done in the swing phase. On the other hand, the ankle plantarflexors (soleus and gastrocnemius) contribute most to lower body power in the stance phase.
This research also shows us that hip extensor and flexor power generated and positive work done in the (early and late) swing phase increase with running speed, and knee extensor and flexor power absorbed and negative work done in the (early and late) swing phase also increase with running speed. These increases in power generated or absorbed and positive or negative work were closely linked to the changes in running speed, indicating that they are key to running performance. Contrary to popular belief work done in the stance phase is not associated with running speed.
Put simply, if we want to run faster, hip extensor and flexor power generated and knee extensor and flexor power absorbed all need to increase.
What is the best way of increasing these types of strength?
In the swing phase, when the hip extensors and flexors are generating power, they are doing so at very high velocities.
This tells us that these muscles are shortening at very high speeds, and are therefore limited by their maximum contraction velocity to a greater extent than their ability to produce maximum force.
Consequently, the best way of improving the ability of the hip extensors and flexors to generate power in the swing phase of sprint running is to use high-velocity exercises, such as jump squats with light loads and kettlebell swings (for the hip extensors) and band-resisted hip flexion and potentially wearable resistance (for the hip flexors).
In the swing phase, when the knee extensors and flexors are absorbing power, they are lengthening. The speed of the muscle action has little effect on force during lengthening muscle actions, and very high forces can be produced.
Essentially, these muscles are largely limited by their ability to withstand high forces while they are lengthening.
Therefore, the best way of improving the ability of the knee extensors and flexors to absorb power in the swing phase of sprint running is to use eccentric training, such as reverse Nordic curls (for the knee extensors) and either Nordic curls or lying leg curls with eccentric overload (for the knee flexors).
How is strength training commonly performed for sprinting?
Sprinting athletes commonly perform blocks of heavy strength training before progressing to blocks of high-velocity strength training. This approach can be seen at various levels, whether progressing from younger to older athletes, or within a single training year for high-level athletes.
While popular, this approach ignores the fact that different muscle groups may benefit from being trained in different ways (to develop different types of strength) and each workout in a block is designed to improve the same type of strength in all muscle groups.
This approach has probably evolved partly due to the widespread acceptance of block periodization models (which are controversial), and partly due to the idea that strength training for athletes should focus on training movements rather than muscles (which is invalid, because we know from motor learning research that improvements in coordination are certainly not transferable from exercises to sporting movements).
Even so, the approach assumes that (1) the blocks of heavy strength training provide some sort of foundational adaptations that can be built upon in the later high-velocity strength training blocks, (2) these foundational adaptations can be retained throughout subsequent high-velocity strength training blocks, and (3) force production during eccentric contractions can be developed optimally using heavy strength training.
Let’s take a closer look at each of these assumptions.
Does heavy strength training produce a foundation of strength for future training blocks?
It is often stated that heavy strength training produces a foundation of strength, or increases general strength, which can be built upon by subsequent training blocks of power training.
Indeed, this is a common claim by proponents of periodization models. However, it does not stand up to scrutiny, if we consider the biological adaptations that result from heavy strength training.
Heavy strength training produces three main transferable adaptations to force production in other movements: (1) increased motor unit recruitment, (2), lateral force transmission, and (3) hypertrophy.
Increased motor unit recruitment increases force production in any movement that uses the same muscle, regardless of velocity. However, we can increase motor unit recruitment with high-velocity exercises, so this is not relevant.
Increased lateral force transmission probably does not improve high-velocity strength because the increases in force per unit cross-sectional area are balanced out by reductions in maximum contraction velocity, so this is also not relevant.
Hypertrophy can theoretically contribute to force production at any velocity. In practice, it contributes much less at higher velocities because it occurs in conjunction with (1) shifts in muscle fiber type from the very fast type IIX to moderately fast type IIA fibers, (2) increases in internal moment arm lengths of the muscle, which require the muscle fibers to shorten faster for the same joint angular velocity, (3) increases in tissue inertia, which occur alongside increased muscle mass, and (4) increases in antagonist coactivation at the joint in fast movements that occur after the heavy strength training that is necessary to produce the muscle growth.
Ultimately, if hypertrophy was really that helpful for high-velocity force production, then high-velocity movements would trigger it to happen, because of the principle of the specific adaptation to imposed demand. This makes it hard to recommend the use of heavy strength training for the hip extensors and flexors in sprinting.
Do we risk losing some beneficial adaptations during blocks of high-velocity training?
When following the popular approach to strength training, which involves sequential blocks of heavy strength training (for all muscle groups) followed by high-velocity strength training (for all muscle groups), the high-velocity phase involves little mechanical loading on the muscle groups.
Since mechanical loading is the key factor that determines muscle growth, this can lead to atrophy of the muscles that previously grew during the heavy strength training block. Similarly, adaptations that cause improved eccentric strength (such as increases in titin or collagen) might also dissipate over time, if the muscles are not exposed to high forces while lengthening.
Atrophy of the hip extensors and flexors may actually partly explain the improved sprinting performance that tends to result in such blocks, since it will occur in conjunction with increased type IIX fiber proportion, decreased internal moment arm lengths of the muscles, and decreased tissue inertia, all of which will improve maximum contraction velocity.
However, atrophy of the knee extensors and flexors will probably be slightly detrimental to sprinting performance, since muscle size is a key contributor to muscle force production during eccentric contractions (along with the force that is produced by titin and collagen).
Ultimately, whether atrophy is a problem during blocks of high-velocity strength training is muscle-specific. It could be a problem if it occurs in the knee extensors or knee flexors, but it is less likely to be detrimental for the hip extensors and hip flexors.
Does heavy strength training optimally increase the ability to produce force in eccentric contractions?
Hypertrophy contributes to force production during lengthening (eccentric) contractions.
However, it is not the sole contributor.
Increases in voluntary activation do contribute substantially, and such changes are likely developed to a greater extent with eccentric contractions than by heavy strength training.
Moreover, it is likely that titin and collagen also adapt inside the muscle. Such changes explain why we can observe increases in involuntary maximum eccentric strength without increases in muscle size or involuntary maximum isometric strength in animal models.
Ultimately, heavy strength training is an inefficient way of increasing eccentric strength, and it probably requires a greater increase in muscle mass to accomplish the same increase in force producing ability while the muscle is lengthening, which is unhelpful for sprinters who want to maximize the amount of force produced while minimizing bodyweight. This makes it hard to recommend the use of heavy strength training for the knee extensors and flexors, when eccentric training could be so easily used instead.
What does this mean for periodization?
Many coaches struggle to balance the needs of sprinting athletes to produce high forces and high velocities in their sport.
Traditional block periodization is limited in its application to this problem. Following this approach, high-level sprinting athletes typically just end up alternating between the ability to produce a high force and a high velocity at different points in the training year.
Using a daily undulating periodization approach is likely no better, given what we understand about the ways in which force is produced. The adaptations that produce force at slow velocities are fundamentally opposed to the adaptations that produce force at high velocities. Triggering one set of adaptations necessarily leads to decreases in the other set.
However, we can fix this problem by training muscles in each workout in the same way as they are used in the sporting movement. The hip extensors and flexors can be trained to produce force at high velocities (jump squats and band-resisted hip flexion), while the knee extensors and flexors can be trained to produce high forces while they are lengthening (Nordic curls and reverse Nordic curls). All of these exercises can be done in the same workout, with the high-velocity exercises performed first.
Periodizing training between high forces and high velocities over the training year (or over an athlete’s career) is simply not necessary or helpful.
Why does heavy strength training appear to work?
Sometimes, we observe concurrent increases in sprinting ability at the same time as athletes are performing heavy strength training. Moreover, many studies have found that heavy strength training can improve sprinting performance in a range of different populations.
If we consider the way in which force is produced in the sprinting movement, this likely happens because heavy strength training increases eccentric (knee extensor and flexor) strength and high-velocity (hip extensor and flexor) strength, albeit to a lesser degree than maximum (slow-velocity) concentric strength, especially in untrained individuals.
Even so, heavy strength training will probably stop working either when the athlete reaches a certain level of ability, and becomes limited by their maximum contraction velocity, or when improvements in body composition cease, and bodyweight therefore has to increase with each incremental increase in muscle mass.
Finally, it is clear that high-velocity strength training improves high-velocity strength to a greater degree than heavy strength training, and eccentric training improves eccentric strength to a greater degree than heavy strength training, which makes using these methods far more efficient.
What is the takeaway?
Heavy strength training is not the best way of producing adaptations that contribute efficiently to force production during the sprinting movement, although it can work, especially in beginners. The neural adaptations it produces can be just as easily attained by high-velocity or eccentric training, and the hypertrophy it produces is not always helpful. High-velocity strength training for the hip extensors and flexors, combined with eccentric training for the knee extensors and flexors, is likely a superior approach.
Although block periodizing strength training for athletes who sprint is popular, training all muscle groups in the same way in each workout for sprinting is arbitrary and inefficient. It creates adaptations that we don’t want or need in some muscles in early training blocks, and then loses adaptations that we want to keep in later training blocks. Always training each muscle group in each workout in the exact way that it is used during sprinting is a much better tactic.