AUTOESTIMA

The data presented in section 5.3 shows another important finding: as time progresses (figures 7, 10, and 13), the differences between subjects in average peak load are reduced. In other words: the standard deviation of all these measurements combined appears to decrease.

To obtain figure 21, the standard deviation of all average peak loads for a single day (in other words, all points from figures like figure 7), is calculated, and for all these days, this average is plotted. Figure 21 clearly shows that the standard deviation does indeed decrease over time.

Although this indicates that all subjects approach the same average peak load over time, this does not directly indicate that all subjects approach the desired average peak load (in this case, 50% BW). Figure 22, however, shows not the standard deviation over each day, but the average peak load (in other words, the average of all points in figures like figure 7). The trend line shows that the average peak load over a single day, appears to approach 50%. Therefore, it can be concluded that all subjects approach the same target value over time, and that this target value is 50% BW. In other words, it can be concluded that biofeedback helps the subjects approach their target load, and that this effect starts from the first training. For the group with a target load of 10 kg, figures 23 and 24 show that both average peak load and SD decline over the days. Average peak loads decrease from 23 kg to 22 kg, and SD from 11 kg to 8 kg. Throughout the first days of measurements, both parameters exceed the limits. However, the displayed decline might indicate that if training is continued for a longer period of time, subjects with a target load of 10 kg might also approach their target load.

42

Previous research by Raaben et al. has suggested that for the 10 kg group, the SD is the most important indicator of feedback effects [20]. Average peak load in that study was reduced from 14 kg to 9 kg following feedback training, and SD from 10 to 6 kg. Differences exist between the study by Raaben et al. and the present study, however. In the former, the average peak load before biofeedback training was within the limits. In the present study, however, the average peak load before biofeedback training greatly exceeded the limit. Even though SD might be the most important indicator of feedback effects in this case, as well, getting the average peak load within the indicated limits should be prioritized in order to minimize stress on the fracture area.

6.3 Long-term learning effect

In section 5.4, the results of long-term biofeedback training are presented. A distinct difference was observed in the subjects with a target load of 50% (subjects 1-4 and 8). Subjects 1 and 3 required only a few days of training, before they could maintain the desired load throughout the entire day, whereas subjects 2, 4, and 8 could not manage this within the first weeks. From the fourth week, however, subjects 2 and 4 managed to maintain the desired load throughout the entire day, as well. These differences appear to indicate different behavior in subjects, or different learning skills. With the small number of subjects per group, it is too early to differentiate between these variables at this point. However, if this effect is confirmed in a larger population, patients with faster learning capabilities could do with fewer training sessions each week. Based on patient characteristics, no cause for the difference between the groups could be found at this point.

For subjects 6 and 7, who were allowed to load only 10 kg, the plots in figure 22 look different from the others. These two subjects were never able to maintain the learning effect for 24 hours. Furthermore, as opposed to subjects 1-5, the learning effect in these subjects appeared to be lost at t=0 several times. This indicates that their weight bearing was, in fact, less adequate than the measurement right before that, without receiving feedback. This could mean that these subjects did not benefit from biofeedback training. Extrapolating that conclusion and stating that patients who are instructed to load 10 kg do not benefit from biofeedback training, however, would be premature. Not only has research shown otherwise [20], but for subjects 6 and 7, other factors might have confounded the measurements. For example, both subjects initially only loaded the affected leg on the toe, since that is how they were initially instructed by the physiotherapist. For this study, they were instructed to maintain a plantigrade stance, and attention was paid to that, but it is possible that these subjects still occasionally loaded the toe only, resulting in occasional underloading.

Loading too much has also occurred in these subjects. All subjects mobilized using a walker, but in the case of subjects 6 and 7, they were required to bear 90% of their weight on their arms. Not only did this result in shoulder pains in both subjects, both might have lacked the strength to bear all their weight on their arms. Furthermore, at the moment in which the weight is transferred from the unaffected leg to the arms, the walker is placed in front of the subject. This causes them to have to bear 90% of their weight on their arms, while not being able to fully extend them. Bearing that much weight on one’s arms is less difficult when the arms are extended, perpendicular to the ground. With the walker in front, the elbows might function as a hinge, resulting in a greater risk of falling. In order to counter this, both subjects might have loaded their affected leg more.

Subject 5’s target loads varied over time. Starting at 50% BW, the target load increased by 10% on days 2, 6, and 10. This caused difficulties in examining the long-term learning effects. Looking at the raw data only, however, shows several interesting findings. Between days 2 and 6 (in other words, target load 60% BW), the average peak load started around 70%, but lowered to around 60% in these few days, resulting in a 48-hour retention at day 5. Between days 6 and 10, the average peak load was stable around 70%, but the

43

SD was often high (up to 14%). This also goes for days 10 to 13, where the average peak load was managed around 80% after starting around 70% on day 10, but SD was consistently too high (up to 12%).

Based on this data, it is not possible to place subject 5 in one of the two groups suggested before. However, it is not adequate to say that subject 5 did not display a learning effect at all. Progress was visible, with the 48-hour retention at day 5 as proof. However, the continuously changing target load made it difficult for the subject to adapt, causing little retention the following days.