Public defence: Mirjam Mellema

Many persons with Lower Limb Amputation (LLA) experience challenges related to mobility with a prosthesis. A sufficient level of mobility is important for the performance of Activities of Daily Living (ADLs) and community participation, and hence, quality of life. Researchers have addressed the need for a more holistic approach to prosthetic mobility.

One important mobility characteristic is the functional capacity, often measured in-laboratory as the energy expenditure (oxygen consumption) for prosthetic walking. Persons with LLA reportedly have a higher energy expenditure during walking than persons without amputation, often quantified as higher oxygen consumption per meter (Energy Cost: EC; VO2 mL kg-1 m-1).

Additionally, persons with LLA often have a declined aerobic capacity, and consequently, they utilize a higher proportion of their peak oxygen consumption (%VO2peak) during walking, resulting in limited capacity to sustain activity. To understand how in-laboratory assessments of functional capacity relates to daily-life ambulation, studies using wearable technologies consistently reported decreased ambulation level in persons with LLA compared to able-bodied persons.

Studies also reported that in-laboratory prosthetic walking is different from real-world behavior in many aspects. To date, there is lacking knowledge about the energy expenditure and perceived exertion of typical ADLs other than normal walking, and how this relates to real-world performance.

Aim

The overall aim of this thesis was to enhance our understanding of daily-life mobility of persons with LLA using a more holistic approach, including three perspectives:

• in-laboratory assessments of functional capacity; walking capacity, aerobic capacity, and energy expenditure and perceived exertion of typical household and community ADLs,
• real-world performance assessments; ambulatory activity level and structure
• the lived experience; balance confidence, health-related quality of life (HRQoL), and personal experiences in light of changed daily routines due to the COVID-19 pandemic restrictions. 

Materials and methods

This thesis include four papers. The first two papers have a cross-sectional study design, of which paper I compared the energy expenditure (oxygen consumption) of five ADL experiments, and the ambulatory activity (monitored with accelerometry) of 21 persons with LLA and 12 sex- and age-matched able-bodied controls (CON).

Paper II examined the relationships between VO2peak, ambulatory activity, and walking capacity (assessed with 2MWT) in 14 persons with LLA.

Paper III was a follow-up, cohort study with a mixed-method approach investigating the impact of the COVID-19 restrictions on ambulatory activity and HRQoL in 20 persons with LLA.

Paper IV was a scoping review addressing the reported outcome measures in studies of real-world ambulation in persons with LLA.

Results

Paper I showed that participants with LLA performed five ADLs tasks at a significantly higher EC, but similar level of VO2 consumption (mL kg-1 min-1) as CON, when walking at a self-selected walking speed, which was significantly lower than CON.

However, LLA reported a significantly higher Rating of Perceived Exertion (RPE) for the vacuuming and marked shopping tasks. For fast walking, LLA had a significantly lower walking speed than CON, but a significantly lower VO2 consumption and similar %VO2peak.

Indications of limited walking capacity in participants with LLA were also observed in daily life, with a significantly lower daily step count, significantly higher proportion of low-intensity ambulation and significantly lower proportion of high-intensity ambulation than CON.

Paper II demonstrated that upper-body VO2peak was significantly correlated with walking capacity, daily step count, and proportion of high-intensity ambulatory activity. Additionally, there was a significant negative correlation between VO2peak and time spent sedentary.

Paper III showed that persons with LLA decreased their prosthetic wear time, but increased their daily step count during the COVID-19 pandemic compared to pre-pandemic. Additionally, the COVID-19 restrictions did not negatively affect HRQoL. Psychosocial aspects, e.g. intrinsic motivation, creativity and health awareness were identified factors that positively influenced ambulatory behavior.

Paper IV reported the increasing use of wearable technologies to monitor real-world prosthetic ambulation, particularly in observational and interventional studies. The most frequently reported outcome measure was related to step count, however, it can be argued whether this outcome measure capture relevant information of real-world prosthetic mobility.

Conclusion

The findings demonstrate that persons with LLA are able to perform various ADLs at a similar level of oxygen consumption as persons without amputation, but at a substantially lower walking speed, which may have negative consequences for community participation.

VO2peak might be a determinant of ambulatory activity level and walking at higher intensities. Moreover, psychosocial factors seem to have a large impact on ambulatory behavior.

Real-world monitoring of ambulatory behavior provide insight into the characteristics of prosthetic mobility and the relationship with in-laboratory measurements, but further improvements in wearable technology and methodology are desired.

The findings from this thesis contribute to the understanding of the physical and perceived effort of ADLs and daily-life mobility in persons with LLA, and support the need for a more holistic approach to prosthetic mobility.