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Tendon stiffness and energy rebound

Running economy

Following the shock of energy rebounding back when the feet hit the ground, flexible tendons wobble more and demand more energy to stabilize the musculoskeletal frame.


A variant of the COL5A1 gene grants an increased muscle-tendon stiffness, resulting in greater energy efficiency and better results among marathon and ultra-marathon runners.

Genetic variation (SNP) in COL5A1 gene affect running economy among marathon runners by tendon stiffness and flexibility


Collagens are a family of proteins that strengthen, connect and support ligaments, bones, tendons, and muscles. Collagen begin as rope-like procollagen molecules, made up of various types of collagen chains.

The collagen molecules arrange themselves into long, thin fibrils. Type V collagen regulates the width (diameter) of those fibrils. Studies suggest that type V collagen also controls the assembly of other types of collagen into fibrils in several tissues.

Type V collagen is produced out of the a1 and a2 chains. The COL5A1 gene encodes for the collagen a1 chain.

Variations in the a1 chain can modulate the biomechanical properties of muscle-tendon units.


Genomic coordinates (GRCh38): 9:134,641,789-134,844,842

A variant form of COL5A1 increases muscle-tendon stiffness and is associated with better running performance.

The T allele variant was significantly over-represented among the fastest runners. The figure below shows average finishing time in an ultra marathon competition, stratified by COL5A1 genotype:

















Marathon and ultra-marathon runners carrying the TT genetic set-up were found to be the fastest, on average.

TT homozygotes were also found to have the tightest tendons, and indeed it is known that stiffer athletes have a more optimal endurance profile. Indeed, stiffer international-level distance runners are more economical in their energy use and stiffer tendons promote economical running.

The rational is that following the shock of energy coming back when the feet hit the ground, flexible tendons wobble more and demand more energy to stabilize the musculoskeletal frame.

In various studies among long-range runners, the ‘‘tightest’’ individuals had a lower VO2, probably because they need less energy to spend on stabilizing and an ability to use the absorbed shock to bounce forward.


The CC genetic set-up hampers running by promoting flexible tendons, which demand more energy to spend.


It is important to note that the COL5A1 gene variants were not found associated with performance in other endurance sports (swimming, bicycling), where smaller shock of energy returns through the tendons.















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