Understanding the Relationships Between Physical Activity, Mental Activity and Fatigue in Knee Osteoarthritis

  • Henrietta Oluwafunmilola Fawole

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Background. Despite the global burden of knee osteoarthritis (OA), the high prevalence of fatigue and its associated disability among individuals with knee OA, research on fatigue in knee OA is still nascent. An important gap in the knee OA fatigue literature is the lack of understanding on how physical activity and mental activity influence fatigue, and further whether physical activity positively or negatively influences fatigue is a crucial and unanswered question. Consequently, there is limited evidence about how to use physical activity interventions for fatigue management among individuals with knee OA.

Aim. The overarching aim of this PhD thesis is to further the understanding of the relationships between physical activity, mental activity and fatigue so as to inform the development of evidence-based fatigue management intervention that is inclusive of physical activity as potential fatigue-modifying or preventive modality for the knee OA population through evaluating secondary data on long-term effects on fatigue and utilising short-interval primary physical activity data on fatigue dimensions in individuals with knee OA.

Methods. In order to do this, two studies were conducted. The first phase synthesised evidence on factors associated with fatigue through a systematic review and best evidence grading. Then using longitudinal approaches, potential determinants of fatigue were identified and causal pathways for mitigating the effects of identified fatigue determinants were evaluated with secondary data over a two-year period. The second phase used primary short-interval data to evaluate the dynamics of fatigue, physical activity, mental activity and its relationship and to investigate the immediate impact of physical activity and mental activity on fatigue through a quasi-experimental design.

Results. The systematic review study found nine studies which evaluated factors associated with fatigue in knee OA, and identified factors included physical function, pain, momentary pain, pain-adjusted physical activity, joint stiffness, depressive symptoms, emotional well-being, quality of life, physical activity, body mass index 2 | and demographics factors. There are currently limited or insufficient levels of evidence on these identified factors. Results of the longitudinal study showed determinants of fatigue at two years to be baseline fatigue, poor physical function (i.e., low walking speed), high depressive symptoms and high comorbidities. Further, the longitudinal mediation study showed that high baseline physical activity was directly associated with lower fatigue at two years particularly in those with moderate to high baseline fatigue. Depressive symptoms or physical function did not mediate the association between physical activity and fatigue. Results from the primary data studies showed varying contributions of physical and mental fatigue to general fatigue throughout the day and the negative influence of within-day general or mental fatigue on subsequent physical activity or mental activity. Moreover, increments in general, physical or mental fatigue after bouts of 10 minutes of physical activity (treadmill walking) or dual-task (treadmill walking and Stroop task) were clinically significant. These findings suggest negative impact on fatigue with short bouts of physical activity and dual-task activity in those with knee OA.

Conclusions. The overall conclusions of the studies presented in this thesis indicate that both physical and mental health-related determinants and activities contribute to general fatigue. Physical activity has the potential to decrease or prevent increase in fatigue over a long-term period but in the short-term, physical activity is likely to be contingent on prior levels of general fatigue. Immediate impact of short bouts of physical activity and dual-task may potentially lead to clinically relevant acute fatigue deterioration. The findings of this thesis provide evidence that could form part of and inform the design of a future intervention that is inclusive of physical activity intervention for fatigue management. In summary, the findings of this PhD provide rationale for further investigation of the mechanism of fatigue determinants; identification of appropriate bout of short-term physical activity that may be optimal in fatigue reduction; investigation of various types of long- and short-term physical activity that considers mental activity impact on different dimensions of fatigue as well as provide a framework for developing an intervention for addressing fatigue among individuals with knee OA.
Date of Award2021
Original languageEnglish
Awarding Institution
  • Glasgow Caledonian University
SupervisorSebastien Chastin (Supervisor), Martijn Steultjens (Supervisor) & Andrea Dell'Isola (Supervisor)

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