Exercise patterns in older adults instructed to follow moderate- or high-intensity exercise protocol – the generation 100 study

Line Skarsem Reitlo; Silvana Bucher Sandbakk; Hallgeir Viken; Nils Petter Aspvik; Jan Erik Ingebrigtsen; Xiangchun Tan; Ulrik Wisløff; Dorthe Stensvold

doi:10.1186/s12877-018-0900-6

Research article
Open Access
Open Peer Review
Published: 10 September 2018

Exercise patterns in older adults instructed to follow moderate- or high-intensity exercise protocol – the generation 100 study

BMC Geriatrics volume 18, Article number: 208 (2018) Cite this article

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Abstract

Background

Making older adults exercise and keeping them in exercise programs is a major challenge. Understanding how older adults prefer to exercise may help developing tailored exercise programs and increase sustained exercise participation in ageing populations. We aimed to describe exercise patterns, including frequency, intensity, type, location and social setting of exercise, in older adults instructed to follow continuous moderate-intensity training (MCT) or high-intensity interval training (HIIT) over a one-year period.

Methods

Frequency, intensity, type, location and social setting (alone vs. together with others) of exercise were assessed using exercise logs from 618 older adults (aged 70–77 years) randomized to MCT or HIIT. All participants completed exercise logs after each exercise session they performed during one year. Pearson Chi-square tests were run to assess the association between intensity, type, location and social setting of exercise with training group.

Results

Both groups performed 2.2 ± 1.3 exercise sessions per week during the year. Walking was the most common exercise type in both groups, but MCT had a higher proportion of walking sessions than HIIT (54.2% vs. 41.1%, p < 0.01). Compared to MCT, HIIT had a higher proportion of sessions with cycling (14.2% vs. 9.8%, p < 0.01), combined endurance and resistance training (10.3% vs. 7.5%, p < 0.01), jogging (6.5% vs. 3.2%, p < 0.01) and swimming (2.6% vs. 1.7%, p < 0.01). Outdoors was the most common exercise location in both training groups (67.8 and 59.1% of all sessions in MCT and HIIT, respectively). Compared to MCT, HIIT had a higher proportion of sessions at a gym (21.4% vs. 17.5%, p < 0.01) and sports facility (9.8% vs. 7.6%, p < 0.01). Both groups performed an equal amount of sessions alone and together with others, but women had a higher proportion of sessions together with others compared to men (56% vs. 44%, p < 0.01).

Conclusion

This is the first study that has followed older adults instructed to perform MCT or HIIT over a one-year period, collected data from each exercise session they performed and provided important knowledge about their exercise patterns. This novel information may help researchers and clinicians to develop tailored exercise programs in an ageing population.

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Background

The world population is ageing and the number of older adults with chronic health conditions and physical limitations is expected to increase. This, in turn, could lead to an increased burden on healthcare services [1]. Regular physical activity is an important component of successful ageing and reduces the risk of developing several age- and lifestyle related diseases such as cardiovascular disease, dementia and type 2 diabetes [2,3,4,5,6,7]. However, making older adults exercise and keeping them in exercise programs is a major challenge [8]. Understanding how older adults prefer to exercise may help developing tailored exercise programs and increase sustained exercise participation in ageing populations.

Many exercise interventions have been conducted under controlled laboratory conditions [9], but we do not know how older adults prefer to exercise when they are not under controlled settings and are free to choose type, location and social setting (e.g. alone vs. together with others) of exercise. Furthermore, it has been shown that high-intensity interval training (HIIT) can induce superior changes in health-related markers compared to continuous moderate-intensity training (MCT) [10,11,12,13], also in older adults [14, 15]. The scientific interest in HIIT has greatly increased during recent years [9], but larger and longer studies under free-living conditions are needed to investigate whether HIIT is feasible as a public health strategy among older adults [9, 16]. Therefore, detailed information about older adults exercise patterns with MCT versus HIIT outside laboratory conditions is of particular interest.

Furthermore, exercise initiatives should include strategies that will appeal to various subgroups of older adults. Disparities in physical activity levels between older women and men exist [17, 18], and sex differences are therefore an important consideration when examining exercise patterns.

The aim of this study was to describe exercise patterns, including frequency, intensity, type, location and social setting of exercise, in older adults instructed to follow MCT or HIIT over a one-year period. We also aimed to describe sex differences in exercise patterns in older adults.

Methods

Study participants

Between August 2012 and June 2013, all men and women born between years 1936 to 1942 (aged 70–77 years), with a permanent address in the municipality of Trondheim, Norway, were invited to participate in a randomized controlled trial, the Generation 100 study. The primary aim of Generation 100 is to determine the effect of five years of exercise training on morbidity and mortality. The Generation 100 study protocol and study sample characteristics have been published previously [19].

In total, 1567 participants (790 women) met the inclusion criteria, fulfilled baseline testing and were randomized 1:1 into an exercise training group or to a control group. The exercise training group was further randomized 1:1 to either MCT or HIIT. Participants in the exercise groups were instructed to fill in exercise logs after each exercise session they performed. Data in the present study is based on the exercise logs from the first year of the intervention. Therefore, only participants in the exercise groups were included in the present study (n = 787). Dropouts in the exercise groups during the first year (n = 123) and those with no exercise logs (n = 46) were excluded. A total of 618 participants (291 women) were included in the analyses (Fig. 1). The study was approved by the Regional Committee for Medical Research Ethics (REK sør-øst B: 2015/945) and all participants gave their written informed consent before participation.

Exercise intervention

The MCT group was prescribed two weekly exercise sessions of 50-min continuous activity at 70% of peak heart rate, or approximately 13 on the Borg 6–20 rating of perceived exertion (RPE) scale [20]. The HIIT group was prescribed two exercise sessions a week with 10-min warm-up followed by 4 × 4 min intervals at 85–95% of peak heart rate, or approximately 16 on the Borg 6–20 RPE scale. The participants were given individual oral and written information about the training methods, including information about frequency, duration, intensity and examples of exercise sessions. The participants were free to exercise individually, with an exercise type and at a location of their own choosing. Every sixth week the participants met for a supervised spinning session where they exercised with a heart rate monitor. These exercise sessions gave the participants an opportunity to control their intensity during exercise. In addition, organized group exercise was offered twice per week for motivational purposes. Attendance to these exercises was voluntary and the activity performed varied between indoor and outdoor activities such as walking, jogging and aerobics [19]. Besides the two prescribed exercise sessions, the participants were free to exercise as desired.

Assessment of exercise patterns

Exercise was defined as planned, structured activities, for instance going for walks, skiing, swimming and doing sports, but also as unplanned activities that the participants experienced as exercise. The participants were asked to fill in exercise logs immediately after each exercise session they performed throughout the year and send them to the research center either in prepaid envelopes monthly, or to use internet-based forms following each exercise session [21]. Exercise frequency was calculated as the mean number of sessions reported per week during the year. To assess intensity of exercise the participants reported their subjective RPE on a Borg scale ranging from 6 to 20 [20]. The participants were asked to report the mean intensity level during the exercise session. Ratings from 6 to 10 were classified as low intensity, 11 to 14 as moderate intensity, and 15 to 20 as high intensity. Duration of exercise was measured with a 4-point scale: less than 15 min, 15–29 min, 30 min to 1 h, and more than 1 h. Less than 15 min and 15–29 min was combined due to a low response rate on these response options (1.1 and 8.7% of the total number of exercise sessions, respectively).

To measure exercise type the participants were instructed to choose from the following response options: walking, jogging, cycling, dancing, cross-country skiing, swimming, golf, resistance training and an open-ended response option. Answers in the open-ended response option were categorized into: combined endurance and resistance training, other type of endurance training (e.g. treadmill, aerobic), domestic activities (e.g. housework, gardening), and other (e.g. bowling, horseback riding). Golf was categorized as “other” due to a low response rate (0.5% of the total number of exercise sessions).

The question used to assess location of exercise had the following response options: home, outdoor in nearby area, nature, gym, indoor- and outdoor sports facility. Indoor- and outdoor sports facility was categorized as “sports facility” due to a low response rate on the outdoor sports facility option (1%). For social setting of exercise, the response options were: exercised alone, exercised together with others, and organized by Generation 100.

Demographics and health characteristics

The baseline testing included clinical examinations, physical tests and questionnaires about health and lifestyle. Age and sex were obtained from the National Population Registry. A previously described questionnaire provided information on physical activity level and sedentary time at baseline [19]. Detailed protocol for assessment of body weight (kg), body height (cm) and body mass index (BMI; kg/m²) is described elsewhere [19]. Testing of peak oxygen uptake (VO_2peak^; mL/kg/min) was performed either as walking on a treadmill or cycling on a stationary bike. The test started with 10 min at a chosen warm-up speed. Approximately every two minutes, either the incline of the treadmill was increased by 2%, or the speed was increased by 1 km/h. The test protocol ended when participants were no longer able to carry a workload due to exhaustion or until all the criteria for a maximal oxygen uptake were reached [22].

Statistical procedures

Sample characteristics are presented as mean ± standard deviation for continuous variables and proportions for categorical variables. Pearson Chi-square test and independent samples t-test were used to assess potential sex differences. For BMI and weight, a non-parametric test (Mann-Whitney U) was conducted due to the lack of normal distribution. Data from the exercise logs are presented as proportions of the total number of exercise logs. Pearson Chi-square tests were run to assess the associations between frequency, intensity, type, location and social setting of exercise with sex and training group. The results were considered statistically significant if the p-value was less than 0.05. All statistical analyses were performed with SPSS 22 (Statistical Package for Social Science, Chicago, IL, USA).

Results

The baseline characteristics of the study participants are presented in Table 1. No differences between the training groups existed at study entry. In both groups, men spent more hours in sedentary behavior and had significantly higher weight, height, and VO_2peak compared to women. Contrary, more women than men performed at least 30 min of daily physical activity (Table 1). The included participants had higher VO_2peak (11%) compared to those with no exercise logs. They also had higher VO_2peak (17%) and height (1.7%) compared to dropouts, but a lower BMI (3.7%) (p < 0.05). A higher proportion of the included participants performed 30 min of daily physical activity compared to the dropouts (77.3% vs. 66.1%, p < 0.05).

Table 1 Sample characteristics of the 618 study participants

Full size table

Frequency and intensity of exercise

The participants completed in total 69 492 exercise logs (33 608 HIIT group) during the year, of which 39 075 were received in prepaid envelopes and 30 417 in internet-based forms. Both groups performed 2.2 ± 1.3 exercise sessions per week. Almost 80% of the sessions in the MCT group were actually performed with moderate intensity (11–14 on the Borg scale), while almost 60% of the sessions in the HIIT group were performed with high intensity (≥15 on the Borg scale) (Fig. 2). In the MCT group, women had a significantly higher proportion of sessions with moderate intensity compared to men (81.7% vs. 74.9%, p < 0.01). In the HIIT group, men had a higher proportion of sessions with high intensity compared to women (63.7% vs. 52.3%, p < 0.01) (Fig. 2). In the MCT group, 9.6, 43 and 47.4% of the sessions had a duration of < 30 min, 30 min to 1 h, and more than 1 h, respectively. The corresponding percentages in the HIIT group were 10.1, 45 and 44.9%.

Exercise type

Walking was the most common exercise type in both training groups (Fig. 3). Compared to HIIT, MCT had a significantly higher proportion of sessions with walking and resistance training. Contrary, compared to MCT, HIIT had a higher proportion of sessions with cycling, combined endurance and resistance training, other types of endurance training (e.g. aerobic, treadmill), jogging, swimming and dancing. There were no group differences regarding cross-country skiing and domestic activities (e.g. housework, gardening) (Fig. 3).

In both groups, men had a higher proportion of cycling, cross-country skiing and jogging sessions compared to women (Fig. 4). Men also had a higher proportion of sessions with combined endurance and resistance training and domestic activities than women. In contrast, women had a higher proportion of walking, swimming and dancing sessions than men. There were no sex differences in resistance training and other types of endurance training (Fig. 4).

Location of exercise

Both groups exercised most frequently outdoors in nearby area and in nature (Fig. 5). Additional analyses showed that outdoors was the most frequently reported exercise location in both warmer (April–October) and colder (November–March) months. The MCT group had a significantly higher proportion of sessions outdoors than the HIIT group. Contrary, compared to the MCT group, HIIT had a higher proportion of sessions at a gym, sports facility and at home (Fig. 5).

In both groups, men had a significantly higher proportion of sessions at a gym compared to women (Fig. 6). Contrary, women had a higher proportion of sessions at a sports facility compared to men. In the MCT group, men had a significantly higher proportion of sessions outdoors compared to women, while the opposite was observed in the HIIT group (Fig. 6).

Social setting of exercise

Both groups performed an equal proportion of exercise sessions alone (MCT: 50%, HIIT: 49.6%) and together with others (MCT: 50%, HIIT: 50.4%). In both groups, women had a significantly higher proportion of sessions together with others compared to men (56% vs. 44%, p < 0.01). The HIIT group had a significantly higher proportion of sessions organized by Generation 100 compared to the MCT group (8.1% vs. 5.9%, p < 0.01).

Discussion

This is the first study that has followed older adults instructed to perform MCT or HIIT over a one-year period, collected data from each exercise session they performed and provided descriptive data on their exercise patterns. The main finding is that both groups to a large degree exercised with the prescribed intensity. MCT had a higher proportion of walking sessions than HIIT, while HIIT had a higher proportion of jogging sessions than MCT. In addition, HIIT had a higher proportion of sessions with cycling, combined endurance and resistance training, swimming and dancing. Both groups exercised more frequently outdoors than indoors and performed an equal amount of sessions alone and together with others.