Muscle-strengthening and conditioning activities and risk of type 2 diabetes: a prospective study in two cohorts of US women

Abstract

Background: It is well established that aerobic physical activity can lower the risk of type 2 diabetes (T2D), but whether muscle-strengthening activities are beneficial for the prevention of T2D is unclear. This study examined the association of muscle-strengthening activities with the risk of T2D in women.

Methods and findings: We prospectively followed up 99,316 middle-aged and older women for 8 years from the Nurses' Health Study ([NHS] aged 53-81 years, 2000-2008) and Nurses' Health Study II ([NHSII] aged 36-55 years, 2001-2009), who were free of diabetes, cancer, and cardiovascular diseases at baseline. Participants reported weekly time spent on resistance exercise, lower intensity muscular conditioning exercises (yoga, stretching, toning), and aerobic moderate and vigorous physical activity (MVPA) at baseline and in 2004/2005. Cox regression with adjustment for major determinants for T2D was carried out to examine the influence of these types of activities on T2D risk. During 705,869 person years of follow-up, 3,491 incident T2D cases were documented. In multivariable adjusted models including aerobic MVPA, the pooled relative risk (RR) for T2D for women performing 1-29, 30-59, 60-150, and >150 min/week of total muscle-strengthening and conditioning activities was 0.83, 0.93, 0.75, and 0.60 compared to women reporting no muscle-strengthening and conditioning activities (p<0.001 for trend). Furthermore, resistance exercise and lower intensity muscular conditioning exercises were each independently associated with lower risk of T2D in pooled analyses. Women who engaged in at least 150 min/week of aerobic MVPA and at least 60 min/week of muscle-strengthening activities had substantial risk reduction compared with inactive women (pooled RR = 0.33 [95% CI 0.29-0.38]). Limitations to the study include that muscle-strengthening and conditioning activity and other types of physical activity were assessed by a self-administered questionnaire and that the study population consisted of registered nurses with mostly European ancestry.

Conclusions: Our study suggests that engagement in muscle-strengthening and conditioning activities (resistance exercise, yoga, stretching, toning) is associated with a lower risk of T2D. Engagement in both aerobic MVPA and muscle-strengthening type activity is associated with a substantial reduction in the risk of T2D in middle-aged and older women.

Figure 1. Dose-response relationship between total muscle-strengthening activity (hours/week) and risk of type 2 diabetes in women from the Nurses' Health Study.

Dotted lines are 95% CI for the trend obtained from restricted cubic spline regression (3 knots) truncated at 7 hours/week (≈99th percentile). Estimates were adjusted for age (months), smoking (never, past, or current), alcohol consumption (0, 1–5, >5 g/d), coffee intake (0, <1, 1–3, 3–5, >5 cups/day), race (white, non-white), family history of diabetes, post menopausal hormone use (never, past, current), intake of total energy, trans fat, polyunsaturated fat to saturated fat ratio, cereal fiber, wholegrain, and glycemic load (all dietary factors in quintiles), aerobic physical activity (0, 1–29, 30–59, 60–150, >150 min/week). p = 0.82 for non-linear response.

Figure 2. Dose-response relationship between total muscle-strengthening activity (hours/week) and risk of type 2 diabetes in women from the Nurses' Health Study II.

Dotted lines are 95% CI for the trend obtained from restricted cubic spline regression (3 knots) truncated at 7 hours/week (≈99th percentile). Estimates were adjusted for age (months), smoking (never, past, or current), alcohol consumption (0, 1–5, >5 g/d), coffee intake (0, <1, 1–3, 3–5, >5 cups/day), race (white, non-white), family history of diabetes, post menopausal hormone use (never, past, current), intake of total energy, trans fat, polyunsaturated fat to saturated fat ratio, cereal fiber, wholegrain, and glycemic load (all dietary factors in quintiles), oral contraceptive use (never, past, current), menopausal status (pre, post), and aerobic physical activity (0, 1–29, 30–59, 60–150, >150 min/week). p = 0.02 for non-linear response.

Figure 3. Dose-response relationship between resistance exercise (hours/week) and risk of type 2 diabetes in women from the Nurses' Health Study.

Dotted lines are 95% CI for the trend obtained from restricted cubic spline regression (3 knots) truncated at 7 hours/week (≈99th percentile). Estimates were adjusted for age (months), smoking (never, past, or current), alcohol consumption (0, 1–5, >5 g/d), coffee intake (0, <1, 1–3, 3–5, >5 cups/day), race (white, non-white), family history of diabetes, post menopausal hormone use (never, past, current), intake of total energy, trans fat, polyunsaturated fat to saturated fat ratio, cereal fiber, wholegrain, and glycemic load (all dietary factors in quintiles), aerobic physical activity (0, 1–29, 30–59, 60–150, >150 min/week), and lower intensity muscular conditioning exercises (0, 1–29, 30–59, 60–150, >150 min/week). p = 0.24 for non-linear response.

Figure 4. Dose-response relationship between resistance exercise (hours/week) and risk of type 2 diabetes in women from the Nurses' Health Study II.

Dotted lines are 95% CI for the trend obtained from restricted cubic spline regression (3 knots) truncated at 7 hours/week (≈99th percentile). Estimates were adjusted for age (months), smoking (never, past, or current), alcohol consumption (0, 1–5, >5 g/d), coffee intake (0, <1, 1–3, 3–5, >5 cups/day), race (white, non-white), family history of diabetes, post menopausal hormone use (never, past, current), intake of total energy, trans fat, polyunsaturated fat to saturated fat ratio, cereal fiber, wholegrain, and glycemic load (all dietary factors in quintiles), oral contraceptive use (never, past, current), menopausal status (pre, post), and aerobic physical activity (0, 1–29, 30–59, 60–150, >150 min/week), and lower intensity muscular conditioning exercises (0, 1–29, 30–59, 60–150, >150 min/week). p = 0.22 for non-linear response.

Figure 5. Dose-response relationship between lower intensity muscular conditioning exercises (hours/week) and risk of type 2 diabetes in women from the Nurses' Health Study.

Dotted lines are 95% CI for the trend obtained from restricted cubic spline regression (3 knots) truncated at 7 hours/week (≈99th percentile). Estimates were adjusted for age (months), smoking (never, past, or current), alcohol consumption (0, 1–5, >5 g/d), coffee intake (0, <1, 1–3, 3–5, >5 cups/day), race (white, non-white), family history of diabetes, post menopausal hormone use (never, past, current), intake of total energy, trans fat, polyunsaturated fat to saturated fat ratio, cereal fiber, wholegrain, and glycemic load (all dietary factors in quintiles), aerobic physical activity (0, 1–29, 30–59, 60–150, >150 min/week), and resistance exercise (0, 1–29, 30–59, 60–150, >150 min/week). p = 0.80 for non-linear response.

Figure 6. Dose-response relationship between resistance exercise (hours/week) and risk of type 2 diabetes in women from the Nurses' Health Study II.

Dotted lines are 95% CI for the trend obtained from restricted cubic spline regression (3 knots) truncated at 7 hours/week (≈99th percentile). Estimates were adjusted for age (months), smoking (never, past, or current), alcohol consumption (0, 1–5, >5 g/d), coffee intake (0, <1, 1–3, 3–5, >5 cups/day), race (white, non-white), family history of diabetes, post menopausal hormone use (never, past, current), intake of total energy, trans fat, polyunsaturated fat to saturated fat ratio, cereal fiber, wholegrain, and glycemic load (all dietary factors in quintiles), oral contraceptive use (never, past, current), menopausal status (pre, post), and aerobic physical activity (0, 1–29, 30–59, 60–150, >150 min/week), and resistance exercise (0, 1–29, 30–59, 60–150, >150 min/week). p = 0.53 for non-linear response.

Figure 7. Muscle-strengthening and aerobic activity according to recommendations – and type 2 diabetes risk.

Women in the category “Insufficient” engage in some activity but less than recommended. Data are pooled estimates (fixed effect) of RR's with 95% CI from multivariable cox regression models adjusted for age (months), smoking (never, past, or current), alcohol consumption (0, 1–5, >5 g/d), coffee intake (0, <1, 1–3, 3–5, >5 cups/day), race (white, non-white), family history of diabetes, post menopausal hormone use (never, past, current), intake of total energy, trans fat, polyunsaturated fat to saturated fat ratio, cereal fiber, wholegrain, and glycemic load (all dietary factors in quintiles), oral contraceptive use (only NHSII: never, past, current), menopausal status (only NHSII: pre, post). Muscle-strengthening and conditioning activities and aerobic MVPA were mutually adjusted.