A mixed methods study of lower limb prostheses in Paralympic sports led to a proposed series of guidelines that could assist in the development of sports policies. The study was conducted by Bryce Dyer, PhD, CSci, MIScT, CTPD, MIED, FHEA, head of research and professional practice in the Department of Design and Engineering at Bournemouth University. Dyer was interested in the controversy revolving around the 2008 performance of sprinter Oscar Pistorius, who wanted to compete in both the Olympics and Paralympics.
“I wanted to attempt to resolve problems like that case that I knew would surface again in the future,” Dyer told O&P News. “When I did a review of the literature, I found the resolution was often either philosophical or exclusively scientifically based, but I felt a hybrid approach that married the two together would be more sensitive, practical and acceptable to the sports stakeholders. I used a mixed method approach, which has not been attempted before when dealing with sports technology.”
Evolution of amputee sprinting
Dyer reviewed amputee sprinting performance to see if any objective data offered evidence of potential unfairness or significant technological impact. He reviewed performance data from the men’s 100-meter sprint event performed at the Paralympic games from 1976 to 2012, which was the longest-standing and consistently held running event for athletes with lower limb amputation. Dyer compared the mean averages of the fastest three runners in each successive Paralympic Games for assessment to the nearest able-bodied equivalent, the Olympic Games. The comparison was used to provide a frame of reference for changes that took place during the time period studied assuming prosthetic limbs are not intended to enhance performance. As noted in the study, both events take place every 4 years; are accessible by the same countries of athlete origin; and have taken place at the same venue using the same facilities since 1992.
“It was hard to compare [the Paralympics and the Olympics] as one group has had more than 100 years to develop, whereas the other [had] just a few decades. However, by looking at how these developed when first introduced but also during the same time frame too, you get an idea of how quickly the performance of sprinting with an amputation has improved,” Dyer said.
Three data sets were compared: amputee sprinting (AS), or the change from Paralympic Games to Paralympic Games between 1976 and 2012; able-bodied modern period (MP), or the change from Olympic Games to Olympic Games between 1976 and 2012; and the able-bodied inception period (IP), or the change from Olympic Games to Olympic Games between 1896 and 1932.
The results indicated that while able-bodied sprinting has shown consistent yet marginal improvements in performance during the time period studied, amputee sprinting has undergone a large magnitude of change in a short time period. Dyer noted a large spike in 1988 amputee sprinting results corresponded with the first widespread use of energy storage-and-release prostheses.
Development of consensus
Dyer used the Delphi method — a group technique utilizing anonymous questionnaires that progressively become more focused — to develop consensus among members of an expert panel on the perception and use of lower limb running prostheses. Experts were chosen for the panel based on their involvement with sports and included three prosthetists, eight disability sport academics, four disability sport athletes, one disability sport governing body member and five disability sport spectators. Consensus was defined as a two-thirds majority agreement or when panelists failed to changed their opinions on two consecutive rounds.
“Not everyone fully agreed on the right way to proceed with how lower limb prosthetics should be dealt with, but we did obtain a five-step series of philosophical ‘beliefs’ that could then be investigated and then backed up with scientific experiments later in the study,” Dyer said. “Ultimately, it was felt the technology needed to be regulated, should only restore functionally what has been lost (or is missing) and should be governed by the biological limb’s performance. This was the first attempt to create a pragmatic approach assessment of such technology.”
The consensus from the three rounds of Delphi surveys stated the following: lower limb prostheses should be classified as equipment and formally legislated when used for competitive running; should be submitted for evaluation if these were not formally approved by the International Paralympics Committee (IPC) before use in competition; should be restorative in nature; and should restore functionality and contribute to limb and stride length of the user “of no greater magnitude than that exhibited by the same region of the athlete’s biological lower limb.” The consensus on functionality does not address participation of bilateral amputees, according to the study.
Study of elite competition
Rather than undertaking a laboratory study, Dyer conducted a quantitative-based analysis of video footage. He evaluated step frequency and symmetry of runners competing T44/43 100-meter final at the 2008 Paralympic Games, the 2011 IPC World Athletics Championships and the 2012 Paralympic Games. An appropriate level of visibility was available in three athletes in the 2008 event, six in the 2011 event and four in the 2012 event.
“I used video footage as a means [to] assess the sport under competitive conditions and assess the elite athletes that much of the controversy [about prosthetic limbs] would center around,” Dyer said. “What happens in a lab and what happens in the field may be different, and this was a great way to find out.”
Dyer looked for the following three types of lower limb behavior: lower limb-to-limb symmetry, or limb-to-limb timing within the measurement precision; lower limb-to-limb asymmetry, or consistent limb-to-limb timing imbalance of greater than 0.04 seconds; and random asymmetry, or single-event limb-to-limb timing imbalance of larger than 0.04 seconds.
The results of the video footage study showed randomized asymmetry behavior did take place in elite 100-meter competition.
Guidelines and recommendations
The consensus from the Delphi study was used to develop a framework for guidelines that were refined with the information from the other analyses. The guidelines were used to propose a dynamic test for amputee sprinters, which would allow for comparison of limb-to-limb performance and statistical reliability, while encompassing the mechanical qualities of the lower limb. Based on prior use of jump tests for sprint performance, Dyer proposed the use of a unilateral drop jump test to assess lower limb running prostheses.
“The [outcomes of] the Delphi study give a great bottom line to how the technology should be perceived, and the proposal of a drop jump provides a means to support it out in the field at events,” Dyer said.
Dyer said the results show a prosthetic limb should be tailored not just for a specific sport, but for the event in which the runner is competing. A limb prescription needs to consider limb-to-limb symmetry, but also the way the prosthesis performs at all points in the race. In addition, “potential athletes need to realize that sprinting with an amputation is increasingly competitive with no slowing down its performance improvement,” he added.
The study also showed the use of prosthetic limbs should be managed and measured for competition. The use of a test like the drop jump also could open up opportunities for amputee sprinters to “cross over” to events like the Olympics, according to Dyer.
“Single amputees can be regulated by matching the performance of their prosthetic limb to their biological limb, and this makes such opportunities manageable. However, for double amputees the problem is complicated and far from resolved. Some of my other research has shown these two different types of athletes should be separate when competing,” he said.
Many possibilities could be explored in future research, but Dyer hopes to see studies focused on double amputees.
“The nature of double amputees does need further understanding and for us to move beyond debate or studies centered on one athlete,” he said. – by Amanda Alexander
- Dyer B. Cogent Engineering. 2016;doi:10.1080/23311916.2016.1158488.
Disclosure: Dyer reports no relevant financial disclosures.