If winter runs feel harder than they should (heavier legs, higher effort at familiar paces, and more soreness afterward), that experience is real and explainable. Cold weather doesn’t just make running uncomfortable; it changes how your muscles, tendons, and joints behave under load.
Cold Muscles Produce Force Less Efficiently
Muscle contraction depends on microscopic structures inside muscle fibers called cross-bridges. These cross-bridges form, pull, release, and repeat. This is the basic process behind muscle contraction and force production. When muscle temperature drops, this cycle slows. Each contraction produces less force, even though the muscle is still contracting. To maintain pace, the nervous system compensates by recruiting more muscle fibers, increasing perceived effort and leading to earlier fatigue.
Cold Increases Tissue and Joint Stiffness
Muscle, tendon, and fascia are viscoelastic tissues whose mechanical behavior changes with temperature. In cold conditions, these tissues become stiffer and less compliant. Joint structures also behave more rigidly, reducing smooth joint excursion during stance. Increased stiffness limits the body’s ability to absorb and redistribute forces passively, shifting more responsibility to active muscular control.
Reduced Elastic Energy Return Increases Active Muscle Work
When warm, the muscle-tendon system stores elastic energy during landing and releases it during push-off, improving running economy. Cold reduces the efficiency of this stretch-shortening cycle. With less energy stored and returned passively, muscles must actively generate force that would otherwise be partially handled elastically. This increases the overall muscular cost of running, even when pace remains unchanged.
Cold, Vasoconstriction, and Fatigue
Cold exposure triggers peripheral vasoconstriction, a normal physiological response that helps preserve core temperature by reducing blood flow to the skin. Although direct measurements of muscle blood flow during outdoor cold running are limited, increased vasoconstriction raises overall cardiovascular and thermoregulatory strain. It is reasonable to infer that this environment contributes to earlier fatigue.
Why You’re Often More Sore After Cold Runs
As tissue and joint stiffness increases and elastic energy return decreases in the cold, muscles take on a greater role in braking and stabilizing movement during stance. To maintain joint stability, the nervous system increases co-contraction around the ankle, knee, and hip, much of which occurs while muscles are lengthening under load (eccentric muscle work).
Eccentric contractions are mechanically demanding and closely linked to muscle soreness. When this increased eccentric load is combined with colder, stiffer tissues that tolerate less strain before micro-damage occurs, post-run soreness becomes more likely, even when training volume and intensity remain unchanged.
How to Reduce the Impact of Cold Running
There are several things you can do to reduce the impact of cold on performance and soreness. Extending your warm-up allows muscle temperature and tissue compliance to improve before higher loads are introduced, while starting at a slower pace and gradually building cadence gives the neuromuscular system time to adapt. Dressing warmly enough to preserve muscle temperature is critical. It is generally better to feel slightly warm than underdressed (as an added bonus there are benefits to heat training). If your legs still feel cold or heavy, that is a signal to save speed or intensity work for another day. Completing mobility work immediately after your run, while tissues are still warm, can help restore range of motion and reduce stiffness.
The Bottom Line
Cold weather increases the cost of running by altering muscle efficiency, tissue and joint stiffness, elastic energy return, and neuromuscular control. These changes shift more of the workload toward active and eccentric muscle action, which is why winter runs often feel harder, fatigue sets in sooner, and soreness is more noticeable afterward. Adjusting warm-ups, early-run pacing, proper clothing, and expectations can help make winter training safer and more productive.
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