skip to Main Content

Increased Shock Absorption in orthotics

Four samples of footbeds were received for assessment of their energy absorption characteristics in the as received condition and after ageing treatments.

The samples were identified as follows:

LASRA Identification
PU I
PU II
EVA I
EVA II

Markings on Sample
Interpod (new)
Interpod (old)
Formthotics Ultimate Foot Comfort
Vasyli Custom Heat mouldable orthotics
for customised prescription

The samples were assessed for their energy absorption properties at the seat region using clause 5.10 of AS/NZS 2210.2. This method can be applied to all footwear.

The test applies increasing load and measures energy absorbed during load increase.

This test was carried out as follows:-
a. as received
b. after compression set testing
c. after 7 days over water at 50°C to assess hydrolysis degradation
d. after a further compression set test on hydrolysis treated samples

The atmosphere inside a shoe can be detrimental to some materials, and this along with compression can result in degradation of energy absorption properties. Hydrolysis treatment was used to assess microclimate degradation of energy absorption properties, along with the affect of compression in the long term.

The results were as follows:

The results showed that in the untreated as received tests the PU II system absorbed more energy than the PU I system, although the PU I system resisted hydrolysis better.

The results showed that in the untreated as received tests the PU II system absorbed more energy than the PU I system, although the PU I system resisted hydrolysis better. However, hydrolysis and compression working in combination were better defended by the PU II system. Compression was a more damaging factor than hydrolysis for the PU or EVA.

In general, the PU systems performed better in all tests than either of the EVA alternatives or the control material. The EVA samples suffered significant loss of energy absorption after compression. EVA I lost almost half of its energy absorption properties after compression set tests, EVA II lost up to a third of its energy absorption properties after compression set.

The PU I and PU II samples lost less energy absorption due to compression although the PU I system suffered more under the combined hydrolysis and compression than the PU II.

The energy absorption test is a dynamic test under increasing energy input, while compression set testing involves a long term constant static loading and measures loss of thickness due to loading in wear over a longer period.

The results showed that in the untreated as received tests the PU II system absorbed more energy than the PU I system, although the PU I system resisted hydrolysis better.

The PU systems both performed better than EVA I, while EVA II did very well in this testing. Both PU systems lost more thickness due to compression than EVA II after hydrolysis treatment. As received, the PU I system was better at withstanding static long term compression than the PU II system, however this was reversed after hydrolysis.

EVA I had no cover fabric, and EVA II was of better peel strength than the PU samples.

EVA I had no cover fabric, and EVA II was of better peel strength than the PU samples.

analyses/assessment by : PGR, GR
data checked by : GMcC
report checked by : TP
date : 04/12/03
signed :
designation of signee : Peter Roy
Technical Officer

Results apply to samples as received. Opinions and interpretations, where these are expressed, are outside the scope of the laboratory’s terms of IANZ registration This information is provided for, or at the request of members in accordance with the Rules of the Association and without liability and may only be reproduced in full.

Translate »
Back To Top