What Does A Marathon Do To Your Body

Running a marathon is an incredible physical and mental challenge that pushes the limits of the human body. As a seasoned marathon runner, I can attest to the transformative effects that this endurance event can have on both the body and mind. In this article, I will delve deep into the physiological changes that occur during a marathon and share my personal insights and experiences along the way.

The Cardiovascular System

One of the most significant changes that takes place during a marathon is the impact on the cardiovascular system. As soon as the race begins, the heart rate increases, pumping more blood to the working muscles. In my own experience, I can feel my heart pounding in my chest, propelling me forward with each step.

The continuous effort of running for such a prolonged duration places immense demand on the heart, strengthening it over time. Regular marathon training has been shown to improve cardiovascular fitness, increase stroke volume (the amount of blood pumped out of the heart with each beat), and lower resting heart rate. These adaptations lead to a more efficient heart that can deliver more oxygen to the muscles during exercise.

Muscle Fatigue and Damage

As the miles add up during a marathon, the muscles in the body start to feel the strain. The repetitive impact of running can result in muscle fatigue and micro-tears in the muscle fibers. This can lead to soreness, stiffness, and a feeling of heaviness in the legs.

Personally, I have experienced the notorious “runner’s wall” around the 20-mile mark. It feels as if my legs have turned to lead, and each step becomes a battle. However, I have also learned through training and experience that pushing through this wall is possible. The body has an amazing ability to adapt and find additional energy reserves to keep going, making the final miles an incredible test of mental fortitude.

Metabolic Changes

A marathon is a demanding endurance exercise that requires a significant amount of energy. To meet this demand, the body undergoes various metabolic changes. The primary source of fuel for marathon runners is glycogen, which is stored in the muscles and liver. During a marathon, glycogen stores become depleted, and the body shifts to use fat as an energy source.

As a long-distance runner, I have noticed the importance of proper nutrition and fueling strategies during training and on race day. Eating a balanced diet rich in carbohydrates helps to optimize glycogen stores, ensuring a steady supply of energy during the race. Additionally, consuming energy gels or sports drinks during the marathon can provide a quick source of glucose to maintain blood sugar levels and sustain performance.

The Immune System

Participating in a marathon places significant stress on the immune system. While moderate exercise can boost immune function, prolonged intense exercise can have the opposite effect. The immune system can become temporarily suppressed, increasing the risk of illness or infection.

As a precaution, it’s crucial to prioritize rest and recovery post-marathon. Giving the body time to heal and rebuild is essential for maintaining overall health and preventing potential immune system compromise. In my own experience, I have found that taking a few days to a week of active recovery, such as light jogging or low-impact cross-training, can help to support immune function and aid in the body’s recovery process.

Mental Resilience

While the physical effects of running a marathon are undeniable, the mental impact is equally significant. Crossing the finish line after enduring 26.2 miles is an incredible achievement that builds mental resilience and self-confidence.

Personally, the mental journey of a marathon is filled with ups and downs. The moments of doubt and fatigue are met with a surge of determination and perseverance. Completing a marathon has taught me the power of setting and achieving goals, managing discomfort, and embracing the strength of the human spirit.


Running a marathon is a true test of the body and mind. It challenges our physical limits, strengthens the cardiovascular system, and pushes us to uncover our inner mental resilience. While the physical toll it takes on the body should not be underestimated, the rewards and personal growth that come from completing a marathon are immeasurable. So, lace up your running shoes, train hard, and embrace the transformative journey of a marathon.