The Impact of Fatigue on Running Form: Posture Breakdown and Energy Waste in the Later Stages of Long Distances

Introduction

Looking at race photos from a marathon, it’s easy to tell which runners are in the first 20 kilometers and which are in the last 20—those in the latter stages have drooping shoulders, shuffling strides, and a forward-and-back sway of the body, clearly different from the upright posture of the earlier stages. This “gait deterioration” phenomenon has a clear scientific explanation, and understanding it can help you target your weaknesses in training and delay the onset of breakdown during a race.

The Main Mechanisms Behind Fatigue-Induced Posture Changes

Maintaining running posture requires two systems to operate continuously: the muscular strength system (maintaining posture and propulsion) and the neuromuscular coordination system (precisely controlling the timing and amplitude of movements). After prolonged running, both systems are affected:

At the Muscular Fatigue Level

• Gluteus maximus and gluteus medius: Control pelvic stability and rear-leg propulsion; when fatigued, the pelvis begins to drop and sway laterally
• Quadriceps: Support knee stability during the stance phase; when fatigued, the ability to control knee flexion declines
• Core muscles: Maintain torso stability; when fatigued, excessive forward lean or backward lean appears
• Calves and Achilles tendon system: When fatigued, the elastic energy storage efficiency of the Achilles tendon decreases, weakening propulsion

At the Neural Fatigue Level

• Central fatigue: The brain’s motor commands to muscles become less precise, and coordination deteriorates
• Proprioceptive degradation: After prolonged vibration and impact, sensory nerve feedback is delayed, and movement responses become sluggish

Quantifying Fatigue-Induced Changes in Running Form

Multiple studies have conducted comparative analyses of running biomechanics before and after a marathon. The main findings are as follows:

The Five Most Common Fatigue-Related Posture Deteriorations

1. Shortened stride + foot landing too close to the center of gravity: Fatigued quadriceps lack the strength to “catch” a longer stride, forcing a shorter stride. This is an instinctive self-protection mechanism, but it also means a drop in speed.

2. Trunk lean back: The hips “sit back” in an attempt to reduce the forward moment, but this actually increases lumbar spine load and lengthens ground contact time.

3. Pelvic lateral drop (Trendelenburg Sign): When the gluteus medius is fatigued, the contralateral pelvis drops during single-leg support, making the gait look like a “waddling walk” to observers, and greatly increasing the risk of iliotibial band syndrome.

4. Arms adducting / swinging laterally: When the shoulders and upper limbs are fatigued, the arms no longer maintain a 90-degree bend and begin to swing laterally, increasing energy expenditure from torso rotation.

5. Head forward + looking down: When the neck muscles are fatigued, the head tilts forward, shifting the center of gravity unevenly forward. For every 2.5 cm of forward tilt, the effective weight borne by the cervical spine and upper back increases by approximately 5 kg.

Training Strategies to Delay Posture Breakdown

Strength training (2 times per week):

1. Glute strengthening: Romanian deadlifts (3×8), hip thrusts (3×12), single-leg bridges (3×15)
2. Core endurance training: Planks over 60 seconds, dead bugs 3×10 reps (slow, emphasizing core tension)
3. Functional lower-limb endurance: Bulgarian split squats 3×10, lateral step squats 3×12

At the endurance training level:

4. “Technical training under fatigue”: In the later stages of a long run (beyond 25 km), deliberately perform 5–10 minutes of technical awareness running, such as checking whether the pelvis is level and whether the arms cross the midline.
5. Tempo runs to improve lactate tolerance: Raise the lactate threshold to delay the onset of deep fatigue.
6. “Ugly running” practice: Deliberately run in a fatigued state to train the nervous system to maintain basic running form even under fatigue.

Race strategy:

7. Even pacing: Cardiorespiratory fatigue in the later stages is a catalyst for posture breakdown; even pacing preserves late-race form better than starting fast and paying for it later.
8. Regular “posture resets”: Every 5 km, do a conscious check: lift the head, relax the shoulders, and confirm core engagement.

Conclusion

Posture breakdown under fatigue is a real challenge every long-distance runner faces, but it is not inevitable. Targeted strength training, an even pacing strategy, and the technical awareness cultivated under fatigue are the three most effective prescriptions for delaying the “breaking point.” The next time you look at photos from the second half of your marathon, don’t just check the time on the clock—also look at your posture. That is the truest guide for your future training.

Related Reading

• Neuromuscular Fatigue in Running: The Science of Recovery After Long Distances
• Core Endurance Training for Runners: Building Postural Stamina for Long-Distance Running
• The Science of Fatigue in Road Running: How Central and Peripheral Fatigue Jointly Determine Your Limits
• Running-Related Lower Back Pain: Analysis of 4 Major Muscle Groups and At-Home Recovery Strategies