The upper body plays an important role in our everyday activities. We would not be able to perform tasks such as reaching, pushing, lifting, pulling, and grasping objects without sufficient upper body strength. During walking and running, our arms help propel us forward by the act of swinging in coordination with the opposite lower limb. The arm swing is what aids in controlling the upward force developed by the leg swing, keeping us moving horizontally, either forward or backward.
The arm swing in running is driven by the shoulder muscles. Even when we try to restrict our arms from swinging, our shoulder muscles are still contracting. While our legs swing during this motion, our torso rotates. The remainder of our upper body muscles, including the abdominals, entire back and chest, and even the neck muscles, control this rotation.
Weak Arms = Fatigue
Runners with poor upper body strength will fatigue much quicker in longer runs. As mentioned above, the biomechanics of running involve the entire body working together to create the running movements of leg and arm swing, pelvic stabilization, and torso rotation. Since the arms contain smaller muscle groups than most of the rest of the body, if they do not have sufficient strength to begin with, once they tire during running, the other muscle groups must begin to work harder throughout the remainder of the run. The shoulder muscles will need to work harder to continue propelling the weak arms, which will cause them to fatigue and then limit the amount of arm motion. At this point the core and torso muscles will need to create a stronger rotation to counteract the leg swing. The pattern will continue the fatigue downwards to the legs. In this case, for whole body endurance purposes, having a stronger upper body will help a runner last much longer.
The Purpose of Good Posture
A component to proper running form is good posture. Running with a forward head posture or rounded shoulders will make it more difficult to swing the arms and rotate the torso efficiently. This may lead to similar fatigue as described above or even injury to other joints below and most likely back pain.
Run Tall Proper posture begins with making sure to run tall—basically keeping the head facing forward with the chin parallel to the ground and keeping the shoulders back. This will help open up the chest and ensure more efficient breathing, improving endurance. Keeping the head in the appropriate position and shoulders back to create this tall posture requires strong upper back muscles. These muscles will pull the shoulders back by squeezing the shoulder blades together. Effective exercises to help achieve this strength are upper back rowing and reverse fly exercises. It is important to also include stretching for the chest and shoulder muscles, as having tightness in these areas will contribute to rounding out the shoulders and preventing a tall posture.
Arm Swing Overall shoulder strength is beneficial since the shoulders are the driving force to the arm swing. Deltoid exercises such as straight-elbow forward and side raises are examples of simple strengthening exercises. Proper running form also includes elbows bent as close to a 90-degree angle as possible and limiting the arms and hands from angling in front of the body. This bent position is the job of the bicep muscles; therefore adding in a few variations of arm curls will help achieve this strength. Another effective way to strengthen all components of the arm swing is mimicking this motion with a pair of light dumbbells while performing a leg exercise such as walking lunges or step-ups.
Stable hips The rest of the upper body, from the mid-back to the lower abdominals, is the main component for the torso rotation and pelvic stabilization in running. The torso should mostly be kept as stable as possible with a rotation that flows with the amount of leg swing. Deep core muscles that connect to the spine are in charge of keeping this stability. Most abdominal exercises such as leg raises, crunches, and planks, should be performed with the pelvis rotated slightly backward as to limit arching the back. This posterior pelvic position will contract these deep core muscles.
Trunk Rotation Rotation is achieved mostly by the obliques in the core, which can be strengthened by floor exercises such as the dead bug and Russian twist exercises. Performing walking lunges with a torso twist to the side of the stepping leg is a great combination exercise for the obliques, as well.
If you are looking to improve running form, endurance, or even set a PR, consider including several exercises for the upper body. Although this means you have to set aside a bit more time for exercise, it will be well worth it. A stronger upper body means more efficient breathing, better posture, and improved biomechanics with every step of running. All of these outcomes will lead to lasting longer while running and decreasing your risk of injury and pain along the way.
Sources
Beattie, Kris, et al, The Effect of Strength Training on Performance Indicators... : The Journal of Strength & Conditioning Research, Online, Aug 19, 2019
Pontzer, H., et al, Control and Function of Arm Swing in Human Walking and Running, Online, Aug 19, 2019