The physical activity levels of older New Zealanders : how active are they?
Abstract
New Zealand research on the physical activity levels of older adults has primarily focused on self-report methodologies and there has been a lack of quantification of what constitutes 'moderate-intensity' physical activity. To determine moderate-intensity physical activity in older adults, 9 male and 9 female subjects (age 72 ± 5 yrs, mass 70.7 ± 11.6 kg, height 165.8 ± 9.4 cm, BMI 25.6 ± 2.5, mean ± sd) were given a medically supervised progressive exercise test on a treadmill. Heart rates (HR) and subjective ratings were taken every minute until the test finished at 8 minutes (n = 17) or when participants were advised not to continue (n = 1). The speed of the treadmill was initially set at 1 or 2 km.h⁻¹ and adjusted each minute based on individuals' subjective rating. From regression analysis of subjective rating and speed with HR we found that a subjective rating of 3 (moderate on the Borg scale) equated to a mean treadmill speed of 4 ± 1 km.h⁻¹ (mean ± sd). At this speed the predicted mean HR was 109 ± 18 min⁻¹. A t-test verified that no significant difference existed between predicted HR scores when using either speed on the treadmill (4 km.h⁻¹) or a rating of 3 on the subjective scale (p=0.62). We conclude that a HR of 109 min⁻¹ is equivalent to moderate-intensity physical activity for older adults and may be used as a benchmark for moderate intensity in subsequent studies on the physical activity levels of older adults.
The second phase of the research assessed what proportion of older adults in Christchurch and Greymouth adhere to New Zealand physical activity guidelines that recommend 30 minutes of moderate-intensity physical activity most, or preferably all, days of the week (Guideline 1). This guideline can also be translated into 2.5 hours of moderate-intensity physical activity per week (Guideline 2). Participants HR were continuously monitored and recorded every minute for four days, from waking in the morning until retirement at night. Sixty-two (31 female, 31 male) older individuals from the Greymouth and Christchurch regions (age 71.6 ± 6.4 yrs, mass 72.4 ± 11.7 kg height 168.4 ± 8.8 cm, BMI 25.4 ± 3.8, mean ± sd) provided full sets of HR data. The physical activity level of participants was assessed through Criteria A, which was determined from our treadmill test. To meet Criteria A participants were required to elevate their HR above 108 min⁻¹ for the number of minutes necessary to meet each guideline. Subjects were deemed to meet Guideline 1 if they accumulated at least 30 minutes of moderate-intensity physical activity on 3 of the 4 recording days and Guideline 2 if they accumulated 86 minutes over the four days.
Using our criteria gained from the treadmill test only 18% of participants engaged in appropriate amounts of physical activity to meet Guideline 1 and 40% of participants complied with Guideline 2. Physical activity adherence diminished with age across the 65-69, 70-74, 75-79 and 80+ age categories. Individuals in the 65-69 year old age group demonstrated the highest levels and those in the 80 years and over group the lowest levels of physical activity compliance. Males were slightly more active than their female counterparts when assessed under Guideline 1 (19% - 16% males and females respectively), although females produced slightly superior levels of compliance than males under Guideline 2 (42% - 39% females and males respectively). Christchurch residents were 1.6 times (95% CL 0.5 - 4.9) more likely to adhere to Guideline 1, and 1.1 times (95% CL 0.9 - 1.1) more likely to adhere to Guideline 2. There was no statistically significant difference between the physical activity participation of participants on weekdays (mean 81 ± 9 min⁻¹) compared to weekend days (mean 81 ± 10 min⁻¹) (p=0.92). When asked to self-report their physical activity participation in the last seven days, 61.3% of participants recorded that they had undertaken at least 30 minutes of physical activity each day in the previous week.
Overall, this study quantified moderate-intensity physical activity for individuals aged 65 years and over in terms of walking speed and heart rate and subsequently determined the percentage of older adults that engage in sufficient levels of physical activity for health. The quantification of what constitutes moderate-intensity for older adults will assist in providing a realistic benchmark for daily physical activity involvement. The low compliance levels of older adults to physical activity guidelines highlight the requirement for active leisure policies and interventions that cater for this ageing population.
