April 30, 2024

Software modifications to strength testing device sufficient to circumvent infringement


Muscle strength testing can be used to provide guidance as to when it is safe for a subject to return from an injury or to proactively identify muscle weaknesses that may pose injury risks. Strength testing has become commonplace in elite sport and is filtering down to amateur level, increasing the market for testing equipment.

Vald Pty Ltd v KangaTech Pty Ltd (No 5) [2024] FCA 333 was a dispute between two manufacturers of strength testing equipment. Kangatech had implemented a software modification in its “KT360” strength testing to remove some functionality in order to work around a patent owned by Vald; Vald argued that its patent was still infringed.

The idea behind the Vald patent was to provide cost-effective testing equipment by measuring the upward force imparted against a restraint during a “Nordic curl” to measure the strength of the knee flexor muscles (primarily the hamstrings).

Nordic curls were a known exercise when the patent was filed. In a bilateral (two-legged) Nordic curl, the subject kneels upright on the ground with their lower legs restrained against movement (e.g. by a physiotherapist holding the subject’s ankles). The subject then slowly leans forward, pivoting around their knees and is only prevented from falling forward by the action of their knee flexor muscles. The subject continues to increase the angle of their lean until they can no longer support themselves and need to put out their hands to catch themselves. The further forward a subject can lean, the stronger their knee flexor muscles, and the more force needed to restrain their lower legs against movement.

The parties agreed that an infringing apparatus must have two securing members, each configured to secure a leg of a subject in position during testing, and at least one sensor to sense a force applied to the restraints. However, each party asserted a different position (based on different approaches to claim construction) as to whether both securing members had to be used during testing and as to what was sufficient for the force to be indicative of the strength of the tested muscles.

The below photos (Vald’s photos, our annotations) show the Kangatech device and two different ways that Vald said it could be used and still infringe Vald’s patent, despite the software modification.

Before the software modification, when a subject performed a bilateral Nordic curl with the restraints attached to the sensor carrier in the position illustrated in the first photo, the KT360 would measure the force applied against the left and right restraints (individually via sensors to which the left and right restraints are connected). The software modification implemented in the KT360 included disabling the sensors and outputting an error message if someone attempted to perform a bilateral Nordic curl.

One of Vald’s arguments as to why the KT360 infringed was that, in the position shown in the first photo, a subject could perform a unilateral (one-legged) Nordic curl, and a force measurement would output for the left restraint indicative of the strength of the left leg. The Judge rejected this argument based on a construction of the patent claims that had the effect that the patent could only be infringed if both restraints were used in a way that produced reliable and accurate measurements.

Another of Vald’s arguments was based on the position shown in the second photo. Vald showed that if kept the left restraint in place and moved the right sensor to a middle sensor position, the KT360 would output force measurements for the left restraint when a bilateral Nordic curl was performed with the legs each in contact with a restraint.

The Judge rejected this argument in view of expert evidence that the position shown in the second photo was an artificial position for performing a Nordic curl because the legs were too close together and hence could not be relied upon to produce a reliable and accurate measurement.

While Vald were ultimately unsuccessful in respect of the modified KT360, the decision confirmed that their patent was valid and that a pre-modification version of the KT360 device infringed. Hence, although Vald have been unsuccessful in getting the KT360 device off the market, Kangatech are still unable to offer bilateral Nordic curl testing as a feature of their device.

The case illustrates that in some circumstances, a software modification may be used to keep a product on the market but that careful thought must be given to how a patent owner might go about showing that the modification is insufficient to avoid infringement.

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