Let’s start with the basics. Quadriceps.

They live on the anterior (front) part of our thigh and are called the QUADriceps because there are four parts to it ( current research states that there may be a 5th quadricep), according to new studies from Grob et al. (2016).

A quick anatomy review  of the quadriceps:

1. Rectus femoris is located in the middle of your thigh.
2. Vastus lateralis lays just lateral (outside) to the rectus femoris.
3. Vastus medialis lays just medial (inside) to the rectus femoris.
4. Lastly, the vastus intermedius lies directly underneath or deep to the rectus femoris (Bordoni et al., 2022).

For consistency and organization, here is another IMPORTANT list for you. This list will help you better understand how vital these muscles are.

1. One of the primary functions of the quadriceps is that it helps extend or straighten the knee. Think kicking your leg from a bent knee to a straight knee position, like if you want to lift your feet to rest them on top of an ottoman. Or better, think of a soccer player who has to go from a loaded bent knee position and then quickly and powerfully extend their knee without injury.
2. The rectus femoris helps us flex our hip or raise our thigh to the chest. When you're sitting down and want to pull your leg up to the ceiling, your rectus femoris helps do this. Not only does it affect our knees, but it also directly impacts our hip stability, function, and health. How does it affect our hip stability, function, and health?
3. The quadriceps as a group directly affects your patella and, therefore, your knee health. (Muraki, S. et al 2015) Does this clarify or elaborate on point number 2?

Why Quadriceps Training?

So now that we know what the quads do let's spell out why it's essential to train. When we run, squat, jump, or walk, our quads have to stabilize our knees and help us move the upper part of our legs (Bordoni et al., 2022).

There are also some connections to the hip with flexion, but we'll return to this. Later today, when you are walking toward a chair, before you sit down, take an extra few steps. Notice how your quadriceps contract as your leg swings forward to help extend the knee?

The three types of muscle actions are concentric, eccentric, and isometric. As your leg straightens, your quadricep works concentrically, meaning the muscle goes from a lengthened position to a shortened one.

The quadricep also works eccentrically to prepare your body to absorb impact, particularly when your foot hits the ground. Eccentric means the muscle is going from a shortened to a lengthened position. Functionally, our quadricep eccentrically contracts to slow and control the rate of our knee swinging during our mid-swing phase.

Photo from: https://www.researchgate.net/figure/Phases-of-the-normal-gait-cycle_fig3_309362425

Our body was built to walk/run/jog and move dynamically. This means our bone and muscle structure were built to absorb ground impact forces. We need our quad strength at an adequate level to help support our knees as we increase these ground impact forces.

Strong evidence supports that quadricep strength is directly related to knee pain and the eventual development of knee osteoarthritis in adults, as found by Muraki S. Et al. (2015). To avoid the development of knee pain and help to prevent injury, we can look to develop greater quadricep strength. Here are a couple of suggestions below:

First and foremost, we want to ensure we can keep good tension in our quads throughout the entire range of motion. One example is maintaining tension and stability through our quads from standing deep into a squat/step up.

Pay close attention to your thigh, how far forward your knees travel and how upright your posture is during a squat (any variation) or step up. A simple wall sit or split squat isometric hold can help you feel your quadriceps and indicate a starting baseline of endurance.

I would encourage you to test yourself by doing sets to fatigue of:30 sec holds with:30 sec rest of wall sits. Rest for 3 min, and then do the same for split squats. Document the difficulty level and if you passed or failed the above mentioned work.

Eccentric Quad Exercises

To functionally train our quadriceps, there must be both a concentric and eccentric component. The exerfly provides a dual benefit based on physics and the principles of levers. The best way to build strength under tensile loads means working eccentrically. As noted previously, we must also learn to work through an entire range of motion.

Therefore using the Exerfly allows anyone to emphasize the eccentric load while still having to work concentrically. The exerfly challenges an individual's eccentric load, push power, and strength within a workout.

The setup of the exerfly forces the user to keep tension in the quadriceps throughout the entire movement and better replicates how the body has to stabilize during gait and dynamic movement.

Here is a simple exercise to try:

Front Squat

Single Leg Step Down

Think of another? Get creative with anterior loading by checking out other exercises on the Exerfly video tutorials.

Flywheel Training Cycles

Eccentric Overload

To be repeated 3x per week.

Now that you know what eccentric movement is, we can tell you you'll benefit most from this workout. On the concentric movement, push up with around 50% of your perceived max power and work closer to 70 - 80% to slow the motion as the exerfly pulls you eccentrically back down to the ground.

Wk 1: 3 x 15 reps : 3 min rest between sets

Wk 2: 3 x 20 reps: 2 - 3 min rest between sets

Wk 3: 4 x 20 reps: 2 - 3 min rest between sets

Wk 4: 5 x 20 reps: 2 - 3 min rest between sets

Wk 5: 4 x 25 reps: 2 - 3 min rest between sets

Wk 6: 3 x 15 reps : 3 min rest between sets

Hypertrophy Phase

Wk 1: 3 sets of 8 at 70- 80%1RM

Wk 2: 4 sets of 10 at 70- 80%1RM

Wk 3: 4 sets of 12 at 60- 70%1RM

Wk 4: 5 sets of 10 at 70- 80%1RM

Wk 5: 5 sets of 12 at 60- 70%1RM

Wk 6: 3 sets of 8 at 80%1RM

Strength Phase

Wk 1: 3 sets of 6 at 70- 80%1RM

Wk 2: 4 sets of 4 at 80- 90%1RM

Wk 3: 4 sets of 3 at 80- 90%1RM

Wk 4: 5 sets of 4 at 85- 95%1RM

Wk 5: 5 sets of 3 at 90 - 95%1RM

Wk 6: 3 sets of 6 at 60%1RM

Now let’s go back and retest the wall and iso-split squats. Were you able to increase the time held?

Why does it matter?

Many adaptive changes occur during eccentric overload training including muscle hypertrophy and changes in motor unit behavior and muscle function (Hedayatpour N, Falla D, 2015). Hypertrophy is defined as the enlargement of muscle fiber cross-sectional area.

This means that there is an increase in the number of myofibrils in each muscle fiber meaning more contractile proteins and a larger diameter of the fibers (Haff, G., Triplett, N., 2016). Collectively we see this on a macro level as feeling a pump or noticing our muscle group become more defined, perceiving it as larger.

You will feel this after completing the workload above on the Exerfly. Studies have found that increases in muscle hypertrophy leads to increases in forces generated by an individual muscle contraction.

Studies state that to have a significant effect, you must conduct hypertrophy workouts an estimated 16 times before the changes become apparent (Haff, G., Triplett, N., 2016). Hypertrophy signals the body to recruit more muscle fibers during maximal contractions.

For the Exerfly, we recommend at least 3x a week for 6 weeks to get the most out of one's time and efforts on the exerfly. Over time, the body learns to contract more fibers to work more efficiently.

The Exerfly does a great job of pushing our bodies into a state of hypertrophy by allowing change to the resistance. The decrease/increase of workload percentage enables the body to be pushed into a state of eccentric overload that is safe and effective.

Achieving this kind of work is difficult with traditional gym equipment because of safety. It is extremely hard to work into these ranges of sets/reps without risk of injury when lifting weights such as a barbell for squats or heavier dumbbells. Yet the hypertrophy phase is critical for the body to build strength and power effectively.

The adaptation of recruiting more fibers is a highly efficient adaptation for muscles to become more efficient with energy. The exerfly is one of the best ways to achieve this adaptation because of its allowance to push the workload without risking safety.

Imagine a single person trying to push a car versus 5 people pushing the car. That's how our motor units begin to recruit when placed under a training regiment that challenges the muscle fibers while they are being lengthened. It disperses the load over more muscle fibers.

With traditional training, this signal of calling for more helpers to push the car is more challenging since there is a need to test the working ability of involved muscles maximally. The last thing we want is for that single individual to strain their back while trying to push the car.

The beauty of the exerfly is that since you don't have to increase the literal weight being placed on the body, the risk of injury decreases substantially.

Putting It All Together

The quads need to be strong to run efficiently. That means having the ability to quickly and powerfully bring the hip in and OUT of extension, good control of knee position, and stabilizing the hip when the foot strikes the ground.

The Exerfly allows for high-quality and efficient eccentric hypertrophy of the quadriceps muscle group. To maximize our strength, we should work into a hypertrophy phase for 6 weeks every 3-4 months (depending on your training needs and timeline).

Hypertrophy allows the body to maximally recruit muscle fibers to get the entire muscle involved and become more efficient with each contraction. Therefore, to have strong quads that can be the most efficient meaning more efficient running, the Exerfly can be utilized to push hypertrophy efficiently and effectively.

Let’s help you get faster by working smarter and harder.

References

1. Arhos EK, Capin JJ, Buchanan TS, Snyder-Mackler L. Quadriceps Strength Symmetry Does Not Modify Gait Mechanics After Anterior Cruciate Ligament Reconstruction, Rehabilitation, and Return-to-Sport Training. Am J Sports Med. 2021 Feb, 49 (2) : 417-425. doi: 10.1177/0363546520980079. Epub 2020 Dec 29. PMID: 33373534;
2. Bordoni, B., & Varacallo, M. (2022) Anatomy, Bony Pelvis and Lower Limb, Thigh Quadriceps Muscle. In: StatsPearls [Internet]. Treasure Island (FL): StatsPearls Publishing; Updated 2022 May 10. https://www.ncbi.nlm.nih.gov/books/NBK513334/.
3. Grob, K., Ackland, T., Kuster, M., Manestar, M., Filgueira, L., (2016) A newly discovered muscle: The tensor of the vastus intermedius. Clin Anatomy. 2016 Mar 29 (2) 256-263. Doi: 10.1002/ca.22680. Epub 2016 Jan 6. Access at https://pubmed.ncbi.nlm.nih.gov/26732825/
4. Haff, G., Triplett, N. (2016). Essentials of Strength and Conditioning. Fourth edition. Champaign, IL, Human Kinetics.
5. Hedayatpour N, Falla D. Physiological and Neural Adaptations to Eccentric Exercise: Mechanisms and Considerations for Training. Biomed Res Int. 2015;2015:193741. doi: 10.1155/2015/193741. Epub 2015 Oct 12. PMID: 26543850; PMCID: PMC4620252.
6. de Hoyo, M., Pozzo, M., Sañudo, B., Carrasco, L., Gonzalo-Skok, O., Domínguez-Cobo, S., & Morán-Camacho, E. (2015). Effects of a 10-Week In-Season Eccentric-Overload Training Program on Muscle-Injury Prevention and Performance in Junior Elite Soccer Players, International Journal of Sports Physiology and Performance, 10(1), 46-52. Retrieved Oct 13, 2022, from https://journals.humankinetics.com/view/journals/ijspp/10/1/article-p46.xml
7. Muraki, S., Akune, T., Teraguchi, M. et al. Quadriceps muscle strength, radiographic knee osteoarthritis and knee pain: the ROAD study. BMC Musculoskelet Disord 16, 305 (2015). https://doi.org/10.1186/s12891-015-0737-
8. Petré, H., Wernstål, F. & Mattsson, C. Effects of Flywheel Training on Strength-Related Variables: a Meta-analysis. Sports Med - Open 4, 55 (2018). https://doi.org/10.1186/s40798-018-0169-5
9. Pietsch, S., & Pizzari, T. (2022). Risk Factors for Quadriceps Muscle Strain Injuries in Sport: A Systematic Review. Journal of Orthopaedic & Sports Physical Therapy, 52(6), 389–400. https://onlinelibrary.wiley.com/doi/abs/10.1034/j.1600-0838.2003.00312.x