The acute and chronic effects of resistance exercise with and without blood flow restriction on fall risk factors in older adults

Blood flow restriction (BFR) is a novel training method in which periods of mild ischemia are applied to the upper thighs using specialized tourniquets, often combined with low-intensity resistance exercise (LI). Anecdotally, this training method alters a series of haemodynamic, metabolic, mechanical, and neurological pathways mimicking the effects observed in traditional high-intensity resistance exercise (HI). However, older adults (60≥ years) adhering to HI resistance exercise can be challenging as this type of training requires a high mechanical load to develop strength, hypertrophy, and neuromuscular adaptations. The importance of maintaining lower limb strength in older adults is evident within the literature as there is a strong link between lower limb strength and fall risk. The purpose of this doctoral thesis is to explore the acute and chronic effects of BFR training through a series of pilot studies on measures associated with postural control. Chapter 4 examined the acute responses to BFR and no-blood flow restriction (NBFR) conditions on quiet standing (double leg and single leg) and gait stability (walking) after performing a fatiguing exercise protocol to either the ankle or knee in healthy young adults. There were minimal changes to quiet standing and gait stability post-exercise for either the ankle or knee irrespective of whether BFR or NBFR. However, muscle torque activation reduced considerably for the tibialis anterior and vastus lateralis after muscle fatigue for the ankle and knee respectively. As there were minimal changes in postural control for both quiet standing and gait stability in young healthy adults, it was of interest to identify whether changes would be similar in older adults. Therefore, Chapter 5 repeated the methods conducted in Chapter 4 with a focus on older adults. The results observed in older adults were similar to those in young adults. There were minimal changes to quiet standing and in gait stability after exercise, regardless of whether BFR or NBFR was applied to the ankle or knee. Although, muscle torque and activation reduced considerably for the tibialis anterior and vastus medialis after muscle fatigue for the ankle and knee, respectively. Collectively, the two acute pilot studies provided crucial information on the effects of postural control and can confirm that when fatiguing either the ankle or knee musculature, there were minimal changes to balance. The findings from Chapters 4 and 5 suggest BFR could be safely applied in young and older adults as there appeared to be minimal effect on postural control. Therefore, combining low-intensity resistance exercise with BFR (LIBFR) may be a suitable training method for clinicians or rehabilitation specialists for early-stage rehabilitation or part of a fall prevention programme in older adults. Chapter 6 investigated the effects of a 6-week LIBFR (35% ~ 1 repetition maximum [1RM]) or HI [high intensity ~ 70% 1RM) resistance programme using the box squat and calve raise exercises to examine a host of quiet standing, gait stability and functional balances tests in addition to neuromuscular, proprioception and indices of strength measured at baseline, mid and post 6-week testing points. The results from this study showed an increase in squat and calf strength post training with an increase in knee extension maximal voluntary isometric contraction (MVIC). The functional tests comprising of the timed up and go, sit-to-stand for time and power, also led to some improvement post-training. Additionally, the error rate for joint position sense and the ability to match strength (force sense) also improved, suggesting that participants improved their accuracy post-training. However, negligible changes in quiet standing and gait stability were observed in both LIBFR and HI groups. It appears that LIBFR exercise could be a good alternative to HI resistance exercise based on the improvements noted in strength and neuromuscular measures over a 6-week training period. However, further investigation is required to determine this point as there were several limitations to each pilot study regarding sample size. Although, despite the low sample size it appears that LIBFR training does not cause any detrimental effects on either quiet standing or gait stability, regardless of whether it is performed in an acute or chronic setting. This type of exercise presents an excellent opportunity to motivate sedentary older adults to engage in resistance training at a low-intensity level, which could lead to better adherence to resistance training programmes and overall physical activity.