Ninety participants passed the eligibility screening tests, with 44 randomised to the intervention group and 46 to the control group. Of the 90 randomised participants, 64 (71%) completed the study. Figure 1 indicates the flow of participants through the study. A subset of 49 participants took part in the lab setting assessments, with 40 completing the study. Baseline characteristics for all randomised participants, and lab subset participants are shown in Table 1. No baseline characteristics or functional test scores were different between completing versus withdrawing participants (p>0.05) (Supplementary file A1).
Outcome data
Table 2 presents functional outcomes, with estimated mean differences between groups at all follow-up measures. See Supplementary file A2 for the mean scores of all outcomes at each timepoint (including between-group comparison).
SPPB strength and balance summed scores increased significantly more in the intervention group than in the control group at every timepoint after baseline. Estimated mean difference between groups at week 4 were 1.73[95% CI 1.31-2.16] (p<0.0001), at week 8 were 1.36[95% CI 0.95-1.77] (p<0.0001), and at week 12 were1.42[95% CI 1.00-1.85] (p<0.0001). Figure 2a shows the changes in SPPB strength and balance summed scores across all timepoints. The 60s STS and stand on left leg increased significantly more in the intervention group than in the control group at every timepoint after baseline assessment, while stand on right leg was significantly improved at week 4 but not 8 and 12. There were no significant differences found in other functional outcomes, process measures or secondary health and wellbeing outcomes.
Subset lab-based physical functional outcomes
Participants in the intervention group significantly increased total SPPB total score at every timepoint compared to baseline versus the control group (Figure 2b). Additionally, the scores of each individual SPPB domain (i.e., strength, balance, and gait speed) were significant improved in the intervention group at these timepoints compared baseline versus the control group (Table 2). 5 reps STS, TUG, and single leg balance on the right leg improved significantly more in the intervention group than in the control group at week-4 and week-8, while ability to balance on the left leg was significantly increased in the intervention group at week 8 only. No significant differences in improvement were observed between groups for the peak force of Keiser leg press, or in flexibility outcomes. Supplementary file A3 displays the mean scores of lab-based measures at each timepoint.
Adherence and acceptability
Completed logbooks were available from 24 intervention participants (54% of starters, 86% of completers). These indicated a mean (SD) number of sessions attempted of 77 (10) for the exercise snacking sessions and 75 (10) for the Tai-chi snacking sessions out of a possible 84. Overall adherence was 90% (152 out of 168) for those completing the intervention, with 7 participants completed all sessions. In the intervention group, 14 participants stopped exercising and withdrew from the study in the first 4 weeks and 2 participants withdrew before the end of week 8. There were 28 (63%) randomised participants who finished the 12-week programme. Based on the data from the 24 available logbooks, over half the intervention participants progressed both exercise and Tai-chi snacking movements to level 2 in the first 4 weeks, and to level 3 during week 5-8. Four participants performed all level 3 movements in the first week, whereas two participants only did level 1 exercise snacking without progression and five participants only did level 1 Tai-chi snacking without progression. Participants had slower progression on single leg weight bearing movements (i.e., single leg split squat and march on the spot in exercise snacking, and heel tipping, stand on one leg, and front heel kick in Tai-chi snacking).
The aggregated mean±SD acceptability scores of the exercise and Tai-chi snacking intervention across weeks 4, 8, and 12 were 3.98±0.32, 4.21±0.34, and 4.08±0.31 out of 5 respectively. Supplementary file A4 contains the individual TFA scores at across the intervention.
Qualitative data suggests most participants found the 12-week progressive exercise and Tai-chi snacking programme accessible and convenient to do in their homes and showed a liking for the ‘snacking’ concept. Specifically, when it comes to participants’ feelings towards the intervention (i.e., affective attitude), participants reported a sense of accomplishment and satisfaction after exercise sessions. Some felt pleased they were active, getting themselves moving, and challenging themselves. Preferences varied, with some favouring the simplicity of exercise snacking and others enjoying the elegance of Tai-chi snacking. Interestingly, some thought Tai-chi snacking movements were more challenging and took more effort to learn/perform, yet they preferred them due to their relaxing nature. Nevertheless, few participants found the programme too easy and short and reported ‘getting bored’ and desired more variety and levels and different options on intensities. In general, the exercise and Tai-chi snacking was found to be achievable, enjoyable, and motivational.
Regarding the perceived amount of effort (i.e., burden), participants who perceived themselves to have poor balance reported Tai-chi snacking to be more physically challenging. Similarly, few participants with special neuromuscular injury histories found some specific movements to be physically demanding. For instance, a female participant reported the upper body movements to be difficult due to her autoimmune muscular problem, and another participant considered truck rotation movements to be difficult due to her past spinal injury Generally most participants found that the programme itself did not take too much time and effort to engage with, however Tai-chi snacking was reported as more time-consuming when learning a new format of exercise as well as its relatively complex movements which demanded more cognitive effort.
Regarding opportunity costs, participants reported that they did not have to sacrifice doing any activities and indicated that the short bout snacking programme only took 20 minutes per day which is convenient, accessible and easy to imbed in their daily routine. Nonetheless, the most common reasons of skipping the sessions were holidays, social activities, house chores, illness, childcare and busy schedules. Participants mentioned that doing the programme at a certain time every day would conceivably enhance the adherence and prevent them from excusing for not doing the exercises.
In terms of perceived benefits, most participants believed the programme improved their physical fitness and mental wellbeing. Notably, participants felt that the programme brought them a better lifestyle and made them feel heathier and more confident on their activities of daily living. One female participant mentioned that ‘’I do feel more confident lifting my arms, or doing things… It is sufficiently a level of change that it does make my life easier. I feel better even about lifting shopping and stuff, because I feel a bit stronger.’’ Most participants noticed that their strength and balance had improved and found that upper body movements were helpful and good for their shoulder flexibility and mobility. Others mentioned that the exercises had strengthened the muscles they rarely used, and stretched and softened their knees and ankles, alleviated their knee and hip stiffness, or improved ankle joint stabilisation and calf muscle relaxation.
In terms of the intervention coherence, participants did not find any movements difficult to learn or to understand, other than one participant who reported that some of the level-3 Tai-chi snacking movements were difficult to understand. Video instructions were deemed useful and indispensable, especially for learning Tai-chi snacking. Some also mentioned that having two models in the videos who were at the same age group as them performing modifications of the exercise movements helped comprehension and motivation. Participants recommended that a single in-person demonstration or personal training session in the beginning of the intervention, and feedback on their performance of movements, may increase their self-efficacy further.
Concerning the ethicality of the programme, participants expressed that short bout basic snacking exercise is attractive and accessible for older adults and felt that the snacking exercise is relevant to people losing their fitness as they get older. A few participants thought that the programme could help sedentary older adults, people lacking confidence on exercising, people with joint or bone injuries or conditions such as osteoarthritis, and even physically inactive mid-aged adults.
Regarding remote assessments, no technological issues were reported other than two reports on the disconnection of the internet. A participant said that ‘’The online assessments were very good. I was impressed with that sort of being able to do it by Zoom when your internet doesn’t let you down!’’. In fact, participants who had not used video calling products enjoyed learning new technics and felt impressed with their technological capability. That said, most participants who underwent both remote and lab-based sessions, preferred lab-based sessions as they made them feel more encouraged and personable. Particularly, some enjoyed performing the leg-press machine (Keiser) and found receiving physical feedback from the researcher nicer than via the screen.
Finally, participants experienced a sense of satisfaction, motivation, and noticed the improved physical function after doing the programme. These factors increased their self-efficacy for exercising, encouraged them to engage in more physical activities, and gave them confidence in trying different exercises. Most participants showed willingness to continue doing the programme, and even lengthen or increase the frequency of the sessions. Accordingly, while the 12-week progressive exercise and Tai-chi snacking programme was considered effective, it also built-up participants’ self-esteem and further improved their abilities of managing activities of daily living and increased their engagement in physical activities. See supplementary file A5 for participant quotes in seven TFA domains.