BIOMECHANISCHE LOOPSCHOENTEST 200ää6

Introduction

Similarly as the years before, the purpose of this test is to map two important biomechanical characteristics, being motion stability and shock reduction, for some popular running shoes on the Belgian market. In this way shoe company representatives are able to compare their products with the competition. The consumers on the other hand have at their disposal some objective information about the biomechanical quality of running shoes available on the Belgian market. This enables runners to make their best choice.

This is the Fifth edition of the yearly running shoe test, this time for the models of 2005.

The shoe selection in this test is confined to models which are specially stabilizing (antipronating) or shock reducting This selection is a cross section of the Belgian market and contains shoes with brand names as Asics, Brooks, Mizuno, Reebok, Nike and for the first time. All tested shoes are represented in the tables below

Biomechanical meaning and interpretation of the measuring variables.

In order to warrant a correct interpretation of the results presented here, it is important to know the exact meaning of the measuring variables representing shock reduction and stability.

Shock reduction

This shoe quality is represented by the following measurement variables.

- the impact plantar pressure P_impact ( this is the maximal magnitude of the heel contact pressure )

- the load rate LRPi_mpact (this the maximal rate at which Pi_mpact increases).

In biomechanics it is commonly accepted that the smaller the impact force P_impact en and the load rate LRP_impact, the better the shock reduction capacity of the selected shoe. Indeed, mot only the magnitude, but also the load rate of the impact force is important, especially for the elastic body structures as tendons, ligaments. The latter are very sensitive to rapid or explosive increases of strain.

In contrast with the past, pressure was measured instead of force, because plantar pressures better represent local overloading than forces. But this will not create large differences as pressure and force are strongly correlated.

Which runners are most in need for shock reduction? These are mostly people with rigid ankle joints resulting in minimal or no normal shock reducing pronation at heel impact. This make them often prone to low back pain or degenerative hip and knee injuries. The occurrence of stress fractures is also a phenomenon that can be associated with a lack of shock reduction.

Stability

As for subtalar stability, the following measurement variables are used: the maximal subtalar pronation PROmax , calcaneal eversion EVmax (c.f. figure at the right) and the respective velocities VPROmax and VEVmax.

In biomechanical podiatry, it is assumed that heel stability increases with decreasing subtalar pronation and calcaneal eversion and with slower respective angular velocities.

Overload and overuse as a consequence of a lack of stability or excess of pronation, may result in typical knee injuries ('runner's knee), all kind of tendinitis (e.g. of the Achilles tendon or plantar fascia), forefoot problems (as metatarsalgia, hallux valgus or hallux limitus), internal muscle aches (as compartment syndrome) etc.

Experimental set-up

Twalve running shoes of 6 different brands were tested. They were selected by the manufacturers and categorized as either shock reducing or stabilizing (antipronating). All shoes are represented in the tables below: table 1 for shock reduction and table 2 for stability. .

Shock reduction was measured with a Footscan plantar foot pressure measurement system of RSscan. Using pressure insoles plantar pressure under foot was measured inside the shoe. The figure below illustrates how the pressures were represented graphically and which measuring sites were analyzed.

A complete analysis also requires kinematic information. Motion analysis techniques were used to investigate heel stability.Therefore a Vicon system ( a computerized video system for motion analysis of a Oxford Metrics) was utilized in order to test the pronation stability of the antipronation shoes.

The subjects , 30 in total, were predominantly physical education students. They were invited to run on a treadmill at a comfortable running speed of 10 km/h. The test shoes were presented in random order.

Tests results

The table below presents de shoes tested for shock reduction

TABEL 1: Shock reduction	Pimpact order ( score in N / cm)		LRPimpact order( score in N/ cm^2/ms )
ASSICS Gel Nimbus IV	3	25.1	2	1.03
BROOKS Glycerine	2	24.0	2	1.04
MIZUNO Wave Rider	1	23.0	1	0.89
NIKE Air Strom Pegasus	3	25.9	2	1.01
PUMA Complete Phasis	3	25.6	5	1.17
REEBOK Premier Ultra	6	29.4	6	1.31

LRP_impact is loading rate of the impact pressure P_imp

CAUTION . These values are and, thereforee, are not comparable with the force values of the test in earlier years.

The results above for the variables P_impact en LRP_impact are graphically represented below.

The shoes represented in table 2 below are designed for stability or antipronation ..

TABEL 2: stability	Evmax ang ( score in ∞ )		PROmax rang ( score in ∞ )			VEVmax rang (score In ∞/s )		VPROmax rang ( score in ∞/s )
ASICS GT2100	6	1.6	6		8.6	2	480	4		522
BROOKS Adrenaline GTS5 (*)	1	-1.9	1		3.6	1	427	1		446
MIZUNO Wave Inspire	3	1.1	2		7.3	2	456	2		498
NIKE air structure	2	-0.3		2	6.9	2	470		4	515
PUMA complete tenos II	3	1.3	2		7.9	2	453	2		482
REEBOK Premier FSM II	3	1.0	2		7.4	6	554	6		620

(*) Brooks Adrelanine scores firts, but de measurement data displayed large variations from one to another subject. Therefore these results should be interpreted with some caution

EV_max represents the maximal eversion of the calcaneus and PRON_max the maximal subtalar pronation, while VEV_max en VPRON_maxare doing this for the respective velocities

The results above are represented below in graphical form.

Discussion of the results

Shock reduction

One should keep in mind when analyzing the figures in tables above, which are the means for all subjects, that the measurement errors should be taken into account. Therefore, differences between the means can only be considered significant when they are at least larger than this error For P_impact and the load rate LRP_mpact the respective measurement errors are about 1 ‡ 1.5 N/cm² and .07 ‡ 0.10 N/cm²/ms .

It is remarkable here that the scores for both variables sim,ultanuously in the same sense , which was not always the case in earlier tests

The best scores for the two shock reduction variables variables were presented by MIZUNO Wave Rider, and its close contender BROOKS Glycerine. The midfield was occupied by ASICS Gel Nimbus (former nr. 1 in earlier tests), NIKE Air Pegasus and PUMA Complete Phasis.

The hardest shoe of the series was the REEBOK Premier Ultra. This shoe may be appropriate for heavyweights, surely not for light runners.

Subtalar stability of the rearfoot

Usually shoes that score well for one of the 4 stability variables, score well for the others too, as is the case for BROOKS Adrenaline GTS5 followed byNIKE Air Structure.

In the middle, one has the MIZUNO Wave Inspire, the PUMA Complete Tenos II and the REEBOK FSM II. This seems quite logical as these shoes are classified as light control shoes.

The ASICS GT2100 scores somewhat lower than in the past where the similar GT2080 was classified as number one.

One should note that as in the past, the scores for eversional and pronational velocities lie quite close to one another making it difficult to differentiate one shoe from another.But here also one should keep the measurement error into account. Therefore differences in pronation or eversion can only be considered significant when they surpass 1∞. For the respective angular velocities the error is about 20∞/s

Ons should notice that, as in the past, the eversion and pronation velocity figures are quite close to each other.

Conclusion

Runners regularly suffering from back problems, stress fractures and degenerative knee injuries, frequently lack shock reduction. They are advised to select a running shoe with good shock reducing qualities. In this sense the MIZUNO Wave Rider, together with the BROOKS Glycerine seems to be the best choice.

Runners coping with overpronation and, therefore, needing a stabilizing shoe, may fare well with the BROOKS Adrenaline GTS5. These are also suitable for people coping with tendon problems due to excessive eversional and pronational velocities.

However, the reader should not forget that the above serves as a general advice when buying a new pair of appropriate running shoes. This advice will by no means replace an individual medical or podiatric examination.

Runners with chronic overuse injuries are always advised to visit a good orthopedist and podiatrist .