Buzz words

Drop, carbon, stack height, and fartlek - running is full of internal jargon and creative expressions. Here we clarify some of the most common terms related to running shoes.

Drop - Angle of attack.

Drop is a measure of the shoe's angle of attack and indicates the difference in height between the heel and forefoot. The height of the heel and forefoot is measured from the ground to the insole. If the heel is 40 mm high and the forefoot is 32 mm, then the drop of the shoe is 8 mm (40 - 32 = 8).

A good drop makes the shoe "roll" for a more efficient stride. However, what constitutes a good drop is very individual. The drop for road shoes is usually between 6 and 12 mm, while trail shoes have a slightly smaller drop to relieve muscle strain when running on uneven surfaces. A drop of 0 mm provides a natural running style, but places great demands on the runner in terms of running technique to avoid injuries to the knees, lower legs and feet.

Finding your own optimal drop takes time. There is no shortcut, it's simply a matter of trial and error.

Stack Height - Thickness of the sole.

Stack height is the thickness of the sole from the ground to the insole and is measured at both the heel and forefoot. In general, the higher the stack height, the more foam and more technologies can fit under the foot, whereas low stack height allows for a lighter shoe while providing a close ground contact and a different running feel.

Shoes with high stack height, from about 30 mm and up, feature ample room and lot of material to work with to create both high comfort and great energy return (responsivity), which provides an efficient drive in the stride. Other technologies, such as carbon plates, can also be fitted in high stack height shoes. Higher shoes are often suitable for volume training as they provide good cushioning and thus protect the body from wear and tear.

Shoes with low stack height, from about 20 mm and down, require more from the runner as the lower cushioning combined with a potentially improper running technique puts more wear on the foot, knee and hip. You also don't get the responsive cushioning that can be achieved with a high stack height shoe. However, many runners with proper running technique find that low stack height shoes provide a superior running feel. So, what is best for each person is often a combination of running technique and individual taste.

Weight - Grams on the run.

Running shoes come in a variety of weight ranges. In general, road shoes are lighter than trail shoes; and the lighter your shoes, the greater your ability to run faster for a long time. During a 10k run, the average runner takes about 10,000 steps. For each step, the shoes must be lifted off the ground, which adds up to a lot of weightlifting if you run a long distance.


Industry practice is to present the weight of a men's shoe in size US9. What is weighed is the total weight of one shoe, including laces and insole.

-210 grams: Racing/intervals shoes for road

300 grams: Volume training shoes mainly for road

300+ grams: Shoes with high stability and extra features such as waterproofing

The heaviest part of the shoe is the rubber in the outsole, which means that trail shoes generally weigh more than road shoes. However, don't shun increased weight; many high-quality trail shoes can be found in the slightly higher weight category.

Carbon - Unparalleled energy return.

Carbon plates in running shoes have become a hot topic in recent years. Properly designed and with a skilled runner in the shoes, these plates provide an unparalleled energy return that contributes to a more efficient stride and faster finishing times. However, a basic prerequisite is a good technique with a strong forward momentum in the stride. For a beginner or recreational runner, it can therefore be difficult to benefit from the positive features of the carbon plate.

A carbon plate made from the right material and with a good geometry helps to relieve the pressure on the large muscle groups such as the thighs and backside of the legs. At the same time, a more efficient stride with better "roll" is achieved (provided proper running technique is used), which means the runner can run faster for a longer time.

For a carbon plate to work optimally, the right foam is needed in combination with the right carbon material and the right geometry. The carbon materials currently used in running shoes vary greatly in quality and therefore also in function. So just because a shoe is equipped with a carbon plate does not necessarily mean that the shoe is a better choice than a more traditional model.

NOTE! Shoes with carbon plates in combination with high stack height and narrow soles are usually a poor choice for demanding trail running as they can become unstable on steep side inclines.

Foam - Power to the midsole.

Foam is a collective name for the materials used in the midsole of running shoes. There are different types of materials designed to meet different needs, and in recent years there has been a huge development in this area.

The optimal foam is made of a lightweight material that provides high cushioning and high energy return. If you also manage to achieve good durability, you have a perfect foam. All foam manufacturers strive for this. However, there's usually a compromise, with more or less of each property.

In general, racing shoes have a foam that is light and offers high energy return but has low durability. Shoes for volume training usually features a foam that provides good cushioning and high durability but lower energy return and higher weight.

Energy return defines the resilience and "bounciness" of the material, how quickly it returns to its original shape (much like the rebound of a bouncy ball when dropped). High energy return gives a more efficient stride at the expense of durability and is generally best suited for hard road surfaces and racing/intervals.