​Rotational protection in MTB helmets: What MIPS and similar systems really offer

​Conclusion from the editor’s perspective

Rotational protection systems address a key weakness in traditional helmet testing: the impact of oblique collisions. The risk of concussions and nerve damage has long been scientifically proven, yet official testing standards have so far failed to incorporate these findings. MIPS, WaveCel, KinetiCore and Koroyd, 360° Turbine and RLS all employ different technical approaches, but studies show that they are all highly effective. However, it is not possible to establish a universally applicable ranking of which helmet generally offers the best protection.
When making a purchase, therefore, it is the specific helmet that matters, not just the safety logo. A good fit, adequate coverage and independent test results remain the most important decision-making criteria. A perfectly fitting helmet without such systems is better than a poorly fitting helmet with a rotational system. Only when the former is the case can MIPS and similar technologies offer genuine added value in helmets. Stefan Frey, BIKE editor

Why rotational forces are dangerous for the brain

A classic bicycle helmet made from EPS foam is primarily designed to absorb the energy of a direct impact. The foam core is deformed in the process, reducing the linear acceleration of the head. Among other things, this protects against skull fractures and serious injuries caused by direct impact forces.

In practice, however, cyclists rarely strike the ground at a perfectly vertical angle. Often, the head slides at an angle over a stone, a root or the ground. The helmet is brought to an abrupt halt, whilst the head inside it continues to move. This causes the head to start turning.

This rotational movement produces a Angular acceleration and a Rotational speed. The brain is not fixed rigidly within the skull, but is surrounded by fluid and connected to the rest of the head via nerve structures. During a rapid rotational movement, different areas of the brain may move to varying degrees. This results in shear movements within the tissue.

From concussions to nerve damage

Long nerve fibres that connect the various regions of the brain are particularly vulnerable. They can be stretched or subjected to strain as a result of the movement. The junctions between the brain, the meninges and the skull are also sensitive to such forces. Rotational movements are therefore associated with concussions and certain forms of diffuse brain injury.

This does not mean that every rotational movement automatically leads to an injury. Key factors include the magnitude and duration of the acceleration, the direction of the impact, the contact area and the specific circumstances. However, research shows that conventional helmet standards have so far covered rotational movements less comprehensively than linear acceleration. This is precisely where modern protection systems come into play.

What is the purpose of anti-rotation systems?

Anti-rotation systems generally follow three different approaches:

• Sliding motion: In the event of an oblique impact, the helmet should be able to move to a limited extent relative to the head.
• Shear movement: Damping elements are designed to absorb the rotational movement and convert some of it into deformation.
• Controlled deformation: Special structures within the helmet are designed to absorb the impact energy before it reaches the head.

The aim is not to completely prevent any movement of the head. A certain amount of relative movement between the helmet and the head may even be desirable, as this ensures that some of the rotational energy is not transferred directly to the head.

It is important to note, however, that these systems reduce certain measured values under specific test conditions. No helmet can reliably prevent a concussion. Furthermore, the level of protection depends heavily on the overall helmet design, the fit, the coverage and the specific nature of the impact.

MIPS: The sliding inner layer

MIPS stands for Multi-Directional Impact Protection System. The best-known principle involves a thin, low-friction inner layer situated between the head and the helmet shell. In the event of an oblique impact, this layer can move to a limited extent. This is designed to prevent the helmet from rotating completely in tandem with the head.

The idea is similar to the brain’s natural protective mechanism. There, too, fluid and layers of tissue allow for a certain degree of relative movement. MIPS applies this principle to the interface between the helmet and the head.

Scientific studies show that helmets with sliding surfaces can reduce rotational acceleration under certain conditions. In the development of the STAR test procedure at Virginia Tech University, helmets with sliding surfaces achieved lower impact values on average than helmets without such systems. Lower STAR values indicate a greater reduction in certain impact loads.

Another study from 2024 compared numerous cycle helmets using linear and rotational metrics. In this study, several of the best-performing models were among the MIPS helmets. At the same time, it became apparent that not every helmet featuring MIPS automatically ranked among the best models. The researchers therefore emphasised that the helmet’s overall performance remains the decisive factor.

What are the practical benefits of MIPS systems?

MIPS can be a useful additional safety feature. The system is particularly effective where an oblique impact causes rotational movement. However, it does not automatically improve a helmet’s fit, ventilation or coverage.

There are also different architectures within the MIPS family. In the case of MIPS Spherical The sliding surface is situated between two EPS layers that can move relative to one another. Other versions are more closely integrated into the padding or the helmet shell. Consequently, the level of protection cannot be determined solely by the presence of the MIPS logo.

WaveCel: Deformable honeycomb structure

WaveCel was developed for Bontrager, Trek’s accessories brand, and utilises a wave-like, cell-like structure inside the helmet. This structure is designed to initially deform upon impact and then partially collapse. At the same time, it allows for a limited amount of sliding movement.

A study published in 2019 compared traditional EPS helmets, helmets with a MIPS sliding surface and helmets with a WaveCel structure in oblique impact tests. In a particularly high-speed test impact at 6.2 metres per second, the MIPS group reduced the measured rotational acceleration by up to 44 per cent compared with the control helmet. In this specific test scenario, the WaveCel group achieved a reduction of up to 73 per cent. In the same test, the estimated risk of a specific brain injury fell by between 32 and 91 per cent for MIPS and between 81 and 98 per cent for WaveCel compared with the control helmet.

These figures are interesting, but should not be interpreted as a general ranking. The study used a limited number of helmet types, impact angles and speeds. The authors themselves point out that further tests under a variety of realistic conditions are necessary. A single laboratory test therefore does not prove that WaveCel offers better protection than MIPS in every accident.

KinetiCore: Integrated predetermined breaking points in the EPS

KinetiCore is a system developed by Lazer that is integrated directly into the EPS foam. The helmet features strategically placed crumple zones. These so-called Controlled Crumple Zones are designed to deform in a controlled manner upon impact, thereby absorbing energy.

The principle differs from that of an additional sliding liner. KinetiCore relies more heavily on the targeted deformation of the helmet core. This is designed to enable the helmet to absorb energy in the event of both direct and oblique impacts. The manufacturer describes the design as an integrated system that does not require an additional inner layer.

Independent laboratory assessments show that the performance of individual helmets with integrated deformation zones can vary considerably. For this reason, KinetiCore should not be equated with MIPS across the board. Both systems pursue a similar aim, but use different technical approaches.

Koroyd: Tubes that collapse in a controlled manner

Koroyd consists of numerous interconnected plastic tubes. In the event of an impact, these tubes are designed to collapse in a controlled manner, thereby absorbing energy. The structure is very light and allows air to pass through, as a large proportion of its volume consists of hollow spaces.

Koroyd is primarily an energy absorber. The system is designed to reduce the direct impact energy and, as a result, limit rotational movement. The manufacturer points to a link between reduced direct acceleration and less rotation in the event of oblique impacts.

Independent research, however, is more cautious on this point. A review of various helmet studies found that, in the datasets examined, Koroyd helmets did not show any statistically significant advantages over conventional helmets. This does not mean that Koroyd is ineffective. It does, however, show that manufacturers’ claims and independent comparative data do not automatically yield the same results.

​Leatt 360° Turbine Technology: Movable damping elements

Leatt focuses on its 360° Turbine Technology consisting of several disc-shaped elements arranged in a ring around the inside of the helmet. These so-called turbines are made of a viscoelastic polymer. They are situated between the head and the EPS core.

In the event of an impact, the elements are designed to deform and thereby absorb energy. At the same time, they allow for limited movement of the head within the helmet. This is intended to reduce the transfer of rotational acceleration. Unlike a simple sliding liner, Turbine Technology is not designed exclusively for oblique impacts. It is also intended to absorb energy at lower linear impact speeds.

The test data published by the manufacturer show varying results depending on the direction of impact. In a test at 4.3 metres per second, Leatt reports that rotational acceleration was reduced by 12 per cent in a frontal impact, by 25 per cent in a side impact and by 28 per cent in a rear impact. In a faster rear impact at 6.1 metres per second, a 38 per cent reduction in the mean maximum rotational acceleration was reported. These results are based on the manufacturer’s own tests and should therefore not be equated with an independent, standardised comparison of all helmet technologies.

To put this into context, it is also worth looking at previous tests. BIKE has already examined the advertised performance figures for 360° Turbine Technology in its own comparison test and concluded that the manufacturer’s claims regarding reduced rotational and linear accelerations could not be fully confirmed. This does not automatically render the basic concept of the system useless, but it does highlight how important the specific helmet and the particular test setup are.

Canyon RLS (Release Layer System): The outer shell yields in a controlled manner

The Release Layer System, in short RLS, takes an unusual approach. The technology is not located between the head and the EPS core, but in an additional outer layer of the helmet.

RLS consists of several outer shell panels, a flexible support membrane and small polycarbonate balls. These balls act as a kind of bearing. In the event of an oblique impact, the connections of the affected panel are designed to come loose first. The panel can then move and roll on the spheres. This is intended to divert some of the tangential impact energy into the movement of the outer shell, rather than directly causing a rotational movement of the head.

The system therefore operates on the principle that “React, Roll, Release”:

• Respond: The connection between the panel and the helmet shell gives way when subjected to a specified load.
• Roles: The balls allow the outer shell to move in various directions.
• Solution: The panel can become partially detached from the shell beneath it, thereby dissipating further rotational energy.

The technical approach differs significantly from MIPS. In the MIPS system, an inner layer moves relative to the head. With RLS, by contrast, the movement is generated further out on the helmet. Whilst this can allow for greater freedom of movement, it also means that the system may be visibly damaged or triggered following a significant impact. A helmet with a triggered RLS must therefore be replaced.

A study published in 2026 in the Journal of Biomechanical Engineering The researchers investigated RLS in urban, road cycling and mountain bike helmets. The researchers tested various impact locations and used several head shapes. According to the published results, RLS was specifically developed as an external rotational protection system that allows relative movement between the outer shell and the helmet core via a rolling bearing structure.

According to Canyon, further tests carried out by the ICube Research Centre at the University of Strasbourg revealed reductions in maximum rotational velocity of between 56 and 66 per cent on average compared with helmets of the same design without RLS. These figures were determined at several impact points. As the system is still relatively new and the published data set is smaller than that for MIPS, the results should be regarded as promising, but not as definitive proof of general superiority.

What impact does RLS have on everyday life?

RLS is of particular interest to riders looking for a helmet featuring external rotational protection technology. The outer shell is designed to absorb movement upon initial contact with the ground, thereby reducing the transmission of rotational force.

The main drawback is its limited availability. As things stand, the technology is primarily associated with new Canyon helmets. Furthermore, the helmet must be replaced once the system has been triggered. As with all rotational impact protection technologies, the following applies: a very good RLS helmet with a poor fit is no better choice than a well-fitting helmet with a different protective solution.

In a Nutshell – Overview of Rotation Systems

• MIPS uses a low-friction inner layer that allows for limited sliding movement.
• WaveCel relies on a deformable cellular structure designed to dissipate rotational and impact energy.
• KinetiCore integrates controlled deformation zones directly into the EPS core.
• Koroyd absorbs energy via collapsing plastic tubes.
• Leatt 360° Turbine Technology combines viscoelastic damping elements with limited head movement within the helmet.
• Canyon RLS shifts the anti-rotation mechanism outwards and allows the shell panels to roll along a support structure and come loose.
• Manufacturer data does not automatically constitute independent research. Particularly in the case of Leatt, the published figures should be interpreted with this in mind.
• RLS has new independent research, but it is significantly newer and has been less extensively studied than MIPS.
• None of the systems guarantees protection against concussion.
• The specific helmet is more important than the brand name of the protective system.
• Fit, coverage, the fastening system and independent test results remain crucial.

Conclusion from the editor’s perspective

Rotational protection systems address a key weakness in traditional helmet testing: the impact of oblique collisions. The risk of concussions and nerve damage has long been scientifically proven, yet official testing standards have so far failed to incorporate these findings. MIPS, WaveCel, KinetiCore and Koroyd, 360° Turbine and RLS all employ different technical approaches, but studies show that they are all clearly effective. However, it is not possible to establish a universally applicable ranking of which helmet generally offers the best protection.

When making a purchase, therefore, it is the specific helmet that counts, not just the safety logo. A good fit, adequate coverage and independent test results remain the most important criteria when making a decision. A perfectly fitting helmet without such features is better than a poorly fitting helmet with a rotation system. Only when the former is the case can MIPS and similar technologies offer genuine added value in helmets.