Caffeine has been described as a sports performance-enhancing substance. However, it is unclear whether it can increase the level of physical activity (PA) in nonathletic individuals. This study investigates the relationship between daily caffeine consumption and (a) daily PA/fitness or (b) intervention-induced changes in PA in women and men. On the basis of responses to a dietary habit questionnaire, which included items on caffeinated beverages, 1,032 Japanese adults, were categorized into lower or higher caffeine consumption groups (relative to the median caffeine consumption). In each group, daily step count; sedentary time; and light, moderate, and vigorous PA outcomes were objectively measured. Physical fitness, including peak oxygen consumption, was also evaluated. The relationship between daily caffeine consumption and the change in the levels of PA was investigated in a subgroup of 202 subjects who participated in a 1-year PA counseling intervention. Women in the higher caffeine consumption group presented higher moderate-to-vigorous PA and step count compared with their counterparts in the lower consumption group (4.0 ± 2.1 vs. 3.3 ± 2.1 MET-hr/day, p < .001; 10,335 ± 3,499 vs. 9,375 ± 3,527 steps/day, p < .001). A significant positive correlation was noted between caffeine consumption and peak oxygen consumption among women (r = .15, p < .001). No caffeine-related effects were noted in men. The lower and higher caffeine consumption groups showed no significant differences in their levels of PA at the end of the 1-year intervention. Therefore, caffeine consumption appears to be associated with higher levels of PA in Japanese women. Further studies are needed to clarify this association.
Julien Tripette, Haruka Murakami, Hidemi Hara, Ryoko Kawakami, Yuko Gando, Harumi Ohno, Nobuyuki Miyatake and Motohiko Miyachi
Yuko Gando, Haruka Murakami, Ryoko Kawakami, Noriko Tanaka, Kiyoshi Sanada, Izumi Tabata, Mitsuru Higuchi and Motohiko Miyachi
It is unclear whether light physical activity is beneficially associated with insulin resistance, similar to moderate and/or vigorous physical activity. This cross-sectional study was performed to determine the relationship between the amount of light physical activity, as determined with a triaxial accelerometer, and insulin resistance.
A total of 807 healthy men and women participated in this study. Physical activity was measured using a triaxial accelerometer worn for 28 days and summarized as light intensity (1.1–2.9 METs) or moderate to vigorous intensity (≥ 3.0 METs). Insulin resistance was evaluated by HOMA_R (FPG [mg/dL] × IRI [μU/mL]/405).
The daily time spent in light physical activity was inversely associated with HOMA_R (r = –0.173, P < 0.05). After adjustment for confounders, the association between light physical activity and HOMA_R remained statistically significant (β = –0.119, P < .05). Light physical activity remained significantly associated with HOMA_R following further adjustment for moderate to vigorous intensity activity (β = –0.125, P < .05). Similar results were observed when light physical activity was modeled as quartiles, especially in elderly women.
These cross-sectional data suggest that light-intensity physical activity is beneficially associated with insulin resistance in elderly Japanese women.
Yuko Hashimoto, Ko Matsudaira, Susumu S. Sawada, Yuko Gando, Ryoko Kawakami, Chihiro Kinugawa, Takashi Okamoto, Koji Tsukamoto, Motohiko Miyachi, Hisashi Naito and Steven N. Blair
Background: There are several studies on the relationship between low back pain and physical activity. However, the results of these studies vary, and the relationship between them remains unclear. Therefore, we conducted a cross-sectional study to evaluate the association between objectively measured physical activity and low back pain in Japanese men. Methods: The study included 4022 Japanese men [average age: 47 (10) y]. Daily amount of moderate to vigorous physical activity and step counts were measured using an accelerometer. Low back pain, drinking and smoking, and lifestyle-related diseases were surveyed using a self-administered questionnaire. A logistic regression model was used to evaluate the relationship between physical activity and step counts with persistent low back pain after adjusting for confounders. Results: Persistent low back pain was reported in 428 participants. The multivariable-adjusted odds ratios of presenting persistent low back pain across quartiles of amount of moderate to vigorous physical activity were 1.00 (reference); 0.93 (95% confidence interval, 0.70–1.22); 0.97 (95% confidence interval, 0.74–1.28); and 0.67 (95% confidence interval, 0.50–0.90); P for linearity = .012. Conclusion: We found a significant inverse relationship between objectively measured physical activity and persistent low back pain.
Ryoko Kawakami, Yuko Gando, Kiminori Kato, Susumu S. Sawada, Haruki Momma, Motohiko Miyachi, I-Min Lee, Steven N. Blair, Minoru Tashiro, Chika Horikawa, Yasuhiro Matsubayashi, Takaho Yamada, Kazuya Fujihara and Hirohito Sone
Background: To examine the association between muscular and performance fitness (MPF) and the incidence of glaucoma. Methods: A total of 27,051 glaucoma-free participants aged 20–87 years underwent physical fitness tests between April 2001 and March 2002. The MPF index was calculated using an age- and sex-specific summed z-score from grip strength, vertical jump, single-leg balance, forward bending, and whole-body reaction time. The participants were divided into quartiles according to the MPF index and each physical fitness test. Participants were followed up for the development of glaucoma, which was defined based on physician-diagnosed glaucoma at an annual health examination between April 2002 and March 2008. Hazard ratios for the incidence of glaucoma were estimated using Cox proportional hazards models. Results: During follow-up, 303 participants developed glaucoma. Compared with the lowest MPF index group, hazard ratio (95% confidence interval) of developing glaucoma was 0.64 (0.46–0.89) for the highest MPF index group (P for trend = .001). Vertical jump and whole-body reaction time were associated with incident glaucoma (P for trend = .01 and <.001, respectively). There were no associations between the other physical fitness tests and the incidence of glaucoma. Conclusion: Higher MPF is associated with lower incidence of glaucoma.