Why the classic crunch might be doing more harm than good for your core

Health · Published 3 October 2026 Swipe more like this →

In short: The crunch is a staple of home workouts, praised for its simplicity and accessibility. Yet, biomechanics experts and recent clinical research suggest this popular movement is often mediocre for strength building and potentially risky for your back. Understanding the mechanics of your core is essential for training safely and effectively.

The crunch is designed to isolate the rectus abdominis by keeping the lower back anchored to the floor, theoretically removing the hip flexors from the movement. However, this isolation comes with trade-offs. Biomechanics professor Stuart McGill has long cautioned against the exercise, noting that it can pose a significant risk of back injury. Unlike more modern alternatives like planks, the crunch is frequently cited as a less effective method for building functional core strength.

Recent clinical research adds nuance to these concerns. A 2024 study involving 54 parous women examined how different exercises affect the abdominal wall, specifically looking at inter-recti distance and linea alba distortion. While the crunch successfully reduced the distance between abdominal muscles supraumbilically, it also caused the highest levels of distortion in the linea alba compared to other movements like the abdominal drawing-in maneuver. This deformation is linked to lower activation of the transversus abdominis, the deep muscle layer responsible for spinal stability.

Despite these findings, the crunch remains a popular test of endurance. Extreme feats of volume have been recorded, such as Sirous Ahmadi completing over 20,000 repetitions in under five hours in May 2024. Earlier, John Peterson demonstrated similar endurance, performing 13,994 crunches in two hours in 2021. While these records highlight human capacity, they do not necessarily validate the exercise as the optimal path to health. For the average person, the challenge is meeting World Health Organization guidelines for muscle-strengthening activities—at least two days per week—without relying on movements that may compromise spinal health or cause unnecessary tissue distortion. Experts suggest that focusing on time-efficient, evidence-based alternatives may be a safer strategy for long-term adherence.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Your daily habits are slowly folding your spine into a curve
• Why your lower back requires slow control rather than explosive power
• Why the world's leading cause of disability is often a mystery to medicine
• The mechanics of building a defined back with three key movements
• The gluteus maximus is the human body's largest muscle and essential for standing upright.
• Is daily flossing actually necessary for your oral health or just a persistent myth?
• Biotin is essential for energy, but those beauty supplement claims are mostly marketing hype.
• Dental plaque is a living, breathing, and highly organized community inside your mouth
• Why the B vitamin alphabet has missing letters and why it matters for energy.
• Why your deodorant does not cause cancer, despite what that 1999 email claimed.
• From ancient sponges to electronic bidets, how humanity cleans itself after using the toilet.
• Is breastfeeding beyond infancy a nutritional powerhouse or a misunderstood parenting choice?

More in Health and fitness · More in Health · Latest · A–Z · All topics