The Biomechanics of Snow Shoveling

My wife calls me Shovel King. Honestly, it has little to do with my proficiency for moving snow; rather, due to some obscure psychological drive, I’ve actually started shoveling our walkways and driveway. It’s not that I didn’t shovel before. It’s just that I was the supreme procrastinator, usually waiting for everyone else to be out there before dragging myself into the cold. I could blame my reticence on an abhorrence to domestic chores, especially outside ones (cut the what?). I rationalized that I didn’t need to shovel since we both drove 4-wheeled drive cars. I dunno? Perhaps it was last year’s heavy snowfall that awakened my inner-shoveler. Or that my father’s sacrosanct shoveling was imparted into my DNA. Regardless, I’ve been out there diligently this winter, braced for more. Kind of like the Forest Gump character – I just got up and started shoveling.

According to Susan Spinasanta, Senior Medical Editor for SpineUniverse (“Tips for Back Pain: Digging Your Way Through Winter”), “many people suffer from muscle fatigue, low back strain, vertebral disc damage, and even spinal fractures during the winter season.”  Each year, an estimated 1,200 deaths are due to heart attacks brought on by snow shoveling. People who have high blood pressure, high cholesterol or smoke are at greater risk. We’ve all heard the cautionary advice regarding the inherent risks associated with snow shoveling. Does this made us better prepared to battle the elements?

Snow shoveling is exercise. Those people contraindicated for physical exertion should take precaution. The rest of us, it is suggested, should warm-up, stretch and consume fluids frequently while shoveling. We are told to take frequent breaks. In Popular Mechanics’ “16 Cardinal Rules for snow Shoveling,” writer Roy Berendsohn discusses proper clothing (“loose-fitting layers”), proper snow removal (“move the snow from the center of the rectangle to the nearest edge”) and teaming up with neighbors to “get the job done quicker.” These are all harmless, innocouous recommendations. From a straight physiological perspective, these guidelines are typically given to anyone performing an aerobic-based exercise routine. In many ways, snow shoveling places a greater demand on the body than 45 minutes of cardio in the gym. Why? Because the during the act of shoveling, states Staurt McGill (professor of Spine Biomechanics at Waterloo University) shovelers “bend over to pick up the snow and then twist to dispose of the snow.”

“Biomechanics dictates that the further the load is away from its axis (fulcrum), the heavier it will feel and this will necessitate that a muscle will need to produce grater amounts of force (torque) to move the load,” explains McGill. Snow shoveling represents a Class 3 lever system, meaning that the axis of rotation (fulcrum) is at the opposite end of the lever arm from the resistance (snow), with the applied force (muscles effort) situated between them. Because this type of lever requires higher force production than is capable in this circumstance, injury potential is high. The resistance of the snow is effectively greater than the arms can overcome. The result is the misuse of the lumbar muscles of the back. To decrease the mechanical disadvantage, McGill suggests keeping the snow closer to your body and bending “your knees and push[ing] your hips back so you can maintain a neutral spine.” Berendsohn agrees that you must use your legs as you move from a “squat position to an upright position,” plus, keeping a hand close to the shovel blade and “not to twist as you throw the snow.”

Leverage aside (note the many ergonimically-correct shovels available), I’m sure someone has determined the muscles involved in picking up and moving a shovel of snow and devised a program specific to strengthen those groups. This is one idea. However, let’s look at it another way. Anything that I hold is essentially a part of my overall (body)weight. The snow is attached to the shovel, the shovel attached to the handle, the handle attached to my hands and my hands are attached to me. By moving me, I am essentially moving the snow that I’m holding. To think of the snow as a heavy object I’m holding carries too much psychological and emotional apprehension (this feel heavy). When you hold a shovelful of snow, your muscles will tense enough to support you and the snow. From there, it’s then a matter of moving you (and therefore the snow) to remove the snow. In between shovels, you should maintain a relaxed, knees slightly- bent posture, with your weight situated on the balls of your feet. Slipping is always a concern. By having your weight on your forefoot, you improve your balance and proprioception of movement. Unstable footing loses the support needed for force production. Use lighter loads, more frequently. Try tipping the shovel blade down to dispose of the snow – allowing gravity to intervene. I sometimes utilized the “pushing the snow” method by allowing my weight to be “held” by the shovel. At the proper blade angle, the snow becomes a poor support for your bodyweight, allowing you to pile up small drifts along the asphalt with little effort.