TITLE: The Effects of Single Long and Accumulated Short Bouts of Exercise on
Cardiovascular Risks in Male Japanese Workers: A Randomized Controlled
Study

  ABSTRACT:
The aim of this study was to determine whether accumulated short bouts of exercise can
achieve the same cardiovascular benefits as a single long bout of exercise in sedentary
male Japanese workers and to compare the programs' relative effects on oxidative stress.
Twenty-three sedentary male workers were randomly assigned into 2 different exercise
programs: a Long-bout group, which performed a single period of continuous exercise
(Long-bout group: 30 min × 1) 3 d per week, and a Short-bouts group, which performed 3
short bouts of exercise (Short-bouts group: 10 min × 3) 3 d per week. Cardiovascular risk
factors, including the plasma thiobarbituric acid-reactive substances (TBARS) level, were
examined at baseline and after both 10 and 20 wk. In the Long-bout group, waist
circumference and maximum oxygen uptake (VO2max) significantly improved after
20 wk. The Short-bouts group demonstrated significant increases in VO2max after
10 weeks and in HDL-C after 20 wk. Plasma TBARS significantly decreased after 20 weeks in
the Long-bout group and tended to decrease (but not significantly) in the Short-bouts
group. These results indicate that accumulated short bouts of exercise are an effective
option, especially for busy workers, for incorporating exercise into one's lifestyle.

BODY.INTRODUCTION:
With the aging of the workforce, the incidence of cardiovascular risk factors such as
dyslipidemia and hypertension has increased in Japan1). One recommended approach to address these issues is an
increase in physical activity2).
However, according to the Survey on State of Employees' Health 2007 by the Ministry of
Health, Labour, and Welfare, Japan, 30.6% of Japanese employees report regular mild or
moderate physical activity, including brisk walking, calisthenics, and jogging3). This represented a slight increase
compared with the previous survey (28.9% in 2002). However, adherence to an exercise program
in Japanese employees is less than desirable4). One reason for employees' low adherence to exercise programs
is lack of available time5).  Many studies have shown that for improvements in physical fitness and body weight, exercise
programs comprising an accumulation of several short sessions per day are as effective as
those comprising longer continuous sessions6,7,8,9,10,11). The Active Guide 2013, issued by the Ministry of Health,
Labour, and Welfare, Japan, also emphasizes that the accumulation of physical activity
throughout the week is important for health promotion2). An exercise program that includes short bouts can be
performed more frequently, especially by employees with limited time available for daily
exercise. In their review, Murphy et al. found that most studies reported
no difference in the effect on cardiovascular fitness between accumulated and continuous
patterns of exercise12).
However, whether accumulated exercise is as effective as continuous exercise in terms of
adiposity, the lipid profile, and glucose metabolism remains unclear.  Oxidative stress is associated with the pathogenesis and progression of such cardiovascular
risk factors as adiposity, high blood pressure, dyslipidemia, and glucose intolerance and is
detectable before the onset of clinically significant disease13,14,15,16). Continuous moderate-intensity exercise potently reduces CV
risk factors and oxidative stress17,
18). However, there
is no study reporting whether accumulated exercise has the same effect as continuous
exercise on oxidative stress.  The aim of this study was to determine if several short bouts of exercise can achieve the
same effects on cardiovascular risk factors in sedentary male Japanese workers as single
long bouts of exercise during a period of 20 weeks and to compare the relative effects of
these exercise programs on oxidative stress.

BODY.METHODS.SUBJECTS:
This was a non-blinded randomized controlled study. Twenty-three sedentary male Japanese
workers with a mean ( ± SD) age of 43.9 ± 11.6 years were recruited through the university
newsletter. The inclusion criteria specified men who did not participate in any vigorous
physical activity (reported exercising <20 min·d−1 on <3
d·wk−1 for the previous 6 months). We also included workers who had some
cardiovascular risk factors (e.g., obesity, mild hypertension, controlled diabetes, and
dyslipidemia) but not a history of cardiovascular disease or of musculoskeletal problems
preventing the use of a cycle ergometer. All subjects had sedentary jobs. Medication
levels were not modified during the study period. Workers were randomly assigned using
random numbers generated by a personal computer to one of the following exercise programs:
the Long-bout group, which performed a single period of continuous exercise for 30 min on
3 days per week, or the Short-bouts group, which performed 3 short bouts of exercise,
10 min each, on 3 days per week. A flowchart depicting the participant selection is shown
in Fig. 1
Fig. 1.Flowchart for participants.. All subjects provided written
informed consent to participate in the present study. This study was approved by the
ethics committee of the University of Occupational and Environmental Health, Japan.

BODY.METHODS.CLINICAL ASSESSMENT:
All subjects underwent complete clinical examination at baseline, after 10 weeks, and
again after 20 weeks. Body weight and height were determined using a portable scale and
body mass index (BMI) was calculated by dividing the weight (kg) by the square of the
height (m2). Waist circumference was measured using a standard
protocol19). Resting
blood pressure with the subject seated was measured 3 times between 8:00 AM and 10:00 AM
using an automatic sphygmomanometer (BP-203RVIII; Nihon Colin, Tokyo, Japan). The mean of
the 3 blood pressure readings was used for further analysis.  Blood samples were collected after nocturnal fasting for at least 12 h. Total cholesterol
(TC), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), fasting plasma
insulin (FPI), and fasting plasma glucose (FPG) were measured. Low-density lipoprotein
cholesterol (LDL-C) was calculated using the Friedewald formula (LDL-C=TC − HDL-C − 1/5 ×
TG). Insulin resistance was calculated using the homeostasis model assessment of insulin
resistance (HOMA-IR) with the formula: HOMA-IR=FPI (μU·ml−1) × FPG
(mg·dL−1) / 405. The plasma level of thiobarbituric acid-reactive substances
(TBARS) was assayed using the fluorescence method, as previously described20, 21). The level of TBARS, which are byproducts of
lipid peroxidation, is a biomarker of the systemic oxidative stress level and is
correlated with cardiovascular disease and its risk factors22).  Maximum oxygen uptake (VO2max) was estimated using a 3-stage graded submaximal
test with a cycle ergometer (ML-1800, Fukuda Denshi, Tokyo, Japan)23). A 6-lead electrocardiogram was
recorded and blood pressure was monitored every 2 min during the test. The workload was
increased by 35, 40, or 50 W every 3 min depending on the subject's age and physical
constitution. VO2max can be used as an index for cardiorespiratory
endurance.

BODY.METHODS.PROTOCOL:
Both the Long-bout and Short-bouts exercise programs were 20 wk long and consisted of
30 min of cycle ergometer exercise per day on 3 days per week. An exercise intensity of
50% VO2max was established for each subject based on the result of the
VO2max test. Exercise intensity could be calculated in watts, and the
participants were instructed to practice exercising by themselves with the cycle ergometer
at the proper intensity. Cycle ergometers were placed near their workplaces so that each
participant could attain access to an ergometer within 5 min. VO2max was
reassessed during the tenth week, and the exercise intensity was adjusted according to the
10-wk VO2max test for the remaining 10 wk. Subjects in the Short-bouts group
were instructed to accumulate 30 min of cycle ergometer activity per day in 3 10-min
sessions separated by intervals of ≥2 h on 3 d per week. Subjects in the Long-bout group
were instructed to perform a single 30-min continuous bout of cycle ergometer activity 3 d
per week. Both exercise programs were self-monitored, and the participants were encouraged
to schedule their exercise times into their daily routines while at work. The subjects
recorded the time of day for each exercise bout and agreed not to make changes to their
diet.

BODY.METHODS.STATISTICAL ANALYSIS:
Statistical calculations were performed with personal computer statistical software (JMP
9.0; SAS Institute, Inc., Cary, USA). Differences in mean values were assessed using
unpaired and paired t-tests for comparisons of 2 variables after confirmation of the
normality of each data distribution using the Shapiro-Wilk W-test. Some data that were not
normally distributed were subjected to logarithmic conversion prior to analysis. Changes
in the cardiovascular risk factors and oxidative stress data were assessed using
multivariate analysis of variance (MANOVA) with 2 factors, time (baseline, 10 weeks, and
20 weeks) and pattern of exercise (Short-bouts vs. Long-bout). The level of statistical
significance was set at p<0.05.  In addition, the effect size (ES) was calculated using G*Power 3, which is a power
analysis program designed as a standalone application to handle several types of
statistical tests24). The
indices of ES were Cohen's d for the paired t-tests and
f or f 2 for MANOVA25). According to standard practice,
the thresholds for small, medium, and large effects were defined as d
values below 0.20, 0.50, and 0.80; f values below 0.10, 0.25, and 0.40;
and f 2 values below 0.02, 0.15, and 0.35,
respectively25).

BODY.RESULTS.CHARACTERISTICS OF THE SUBJECTS:
No medical complications occurred during the study. As shown in Table 1Table 1.Baseline characteristicsShort-bouts, n=12, mean ± SD(range)Long-bout , n=11, mean ± SD(range)pbAge (yr)43.3 ± 12.4(27–63)44.5 ± 11.1(27–59)0.822 SBP (mm Hg)122.5 ± 11.2(105.3–140.6)118.6 ± 8.9(104.3–131.7)0.374 DBP (mm Hg)77.5 ± 6.8(67.0–89.7)75.1 ± 6.1(67.0–85.0)0.370 PR (bpm)76.8 ± 12.4(60.3–115.7)73.7 ± 12.4(60.0–90)0.567 BW (kg)74.1 ± 8.5(59.7–87.0)73.3 ± 11.4(57.5–89.7)0.856 BMI (kg·m–2)26 ± 2.4(22.7–32.0)25.6 ± 3.9(20.8–32.1)0.760 Waist circumference (cm)89.5 ± 5.1(83.5–101.2)89.9 ± 7.6(79.8–99.4)0.895 V·O2max
(mL·kg–1·min–1)a35.1 ± 4.5(26.6–46.4)38 ± 7.5(29.8–53.3)0.280 TC (mg·dL–1)212.8 ± 32.4(169–281)201.5 ± 20(167–234)0.331 HDL-C (mg·dL–1)
a51.8 ± 13.9(33–81)47.5 ± 9.2(38–62)0.451 TG (mg·dL–1) a150.4 ± 82.5(66–356)143.1 ± 79.4(74–348)0.787 LDL-C (mg·dL–1)130.8 ± 29.5(92.8–176.2)125.3 ± 27.1(71.4–159.2)0.645 FPI (μU·mL–1) a8.9 ± 3.6(3.4–16.4)7.7 ± 3(2.4–13.8)0.449 FPG (mg·dL–1) a124.7 ± 46.1(96–266)100.5 ± 7.1(91–112)0.049 HOMA-IR a2.64 ± 1.00(0.81–4.41)1.95 ± 0.9(0.54–3.82)0.127 TBARS (μmol·L–1)
a0.28 ± 0.05(0.20–0.36)0.28 ± 0.05(0.22–0.37)0.999 Smoking0.465 Current smoker10Ex-smoker54Non-smoker67Alcohol consumption0.901 Almost every day98Occasional drinker33Medication–Antihypertensive agent32Oral anti-diabetes agent10Lipid-lowering agent01Type of a Job0.509 Researcher67Clerical worker64Short-bouts = three 10-min exercises d–1 on 3 d week–1;
Long-bout = 30-min exercises d–1 on 3 d weeks–1.SBP: systolic blood pressure, DBP: diastolic blood pressure, PR: pulse rate, BW: body
weight, BMI: body mass index, V·O2max: maximum oxygen uptake, TC: total
cholesterol, HDL-C: high-density lipoprotein cholesterol, TG: triglyceride, LDL-C:
low-density lipoprotein cholesterol, FPI: fasting plasma insulin, FPG: fasting plasma
glucose, HOMA-IR: Homeostasis model assessment of insulin resistance, TBARS:
thiobarbituric acid reactive substances. a: for analyses these continuous values were
log-transformed. b: p for unpaired t-test or
χ2 test., with the exception of FPG, there were no significant
differences in age, blood pressure, heart rate, body weight, BMI, waist circumference,
VO2max, lipid profile, FPI, HOMA-IR, or plasma TBARS between the groups at
baseline. There were also no differences between the groups with respect to the subjects'
smoking and drinking habits. Three subjects in the Short-bouts group and 2 subjects in the
Long-bout group were taking antihypertensive medication, 1 in the Short-bouts group was
using an oral anti-diabetes agent, and 1 in the Long-bout group was taking medication for
hyperlipidemia (Table 1). An additional 2
subjects were taking medication for other diseases. Subjects did not alter their
medications during the intervention. Thirteen of the subjects were researchers, and the
others were clerical workers in the university; there was no significant difference in job
type between the 2 groups (p=0.51). The percentages of the actual total
exercise duration (of the 1,800 min prescribed) reported by subjects in the Long and
Short-bouts groups over the entire 20 weeks were 68.9% (1,239 ± 670 min) and 55.5% (999 ±
528 min), respectively (p=0.35).

BODY.RESULTS.GROUP DIFFERENCES:
In the Long-bout group, waist circumference and VO2max significantly improved
after 20 wk, whereas the DBP after 10 weeks showed a significant increase compared with
the baseline value (Table 2Table 2.Changes in anthropometric measures, blood pressure, predicted maximum oxygen
uptake, and glucose and lipid metabolism of subjects from pre- (baseline) to mid- (10
wk) and post- (20 wk) training for the long-bout and short-bouts groupsShort-bouts (n=12)Long-bout (n=11)TimeTime × Group10 wk-baselinepbES (d)20 wk-baselinepbES (d)10 wk-baselinepbES (d)20 wk-baselinepbES (d)pcES (f)pcES (f 2)Δ SBP (mm Hg)2.6 ± 7.10.2290.37 9.6 ± 10.50.0090.91 1 ± 7.90.6830.13 0.7 ± 11.30.8430.06 0.1090.50 0.1830.39 Δ DBP (mm Hg)3.2 ± 4.30.0240.74 8.1 ± 7.40.0231.09 2.1 ± 2.60.0230.81 1.8 ± 6.20.3680.29 0.0040.87 0.1110.44 Δ PR (bpm)–3.5 ± 11.80.3290.30 –5.7 ± 210.3720.27 –0.8 ± 7.80.7420.10 –1.4 ± 12.90.7170.11 0.6110.22 0.6740.19 Δ BW (kg)–0.15 ± 1.30.6980.12 –0.48 ± 2.860.570.17 –0.62 ± 1.280.140.48 –0.49 ± 1.710.3630.29 0.3960.31 0.5510.20 Δ BMI (kg·m–2)–0.05 ± 0.470.7190.11 –0.22 ± 1.030.4710.21 –0.28 ± 0.490.0880.57 –0.23 ± 0.710.3010.32 0.2970.36 0.3360.43 Δ Waist (cm) –0.66 ± 1.630.190.40 –1.31 ± 3.30.1960.40 –1.41 ± 2.250.0650.63 –2.19 ± 2.470.0150.89 0.0330.64 0.6720.20 Δ Ln
V·O2max(mL·kg–1·min–1)a0.024 ± 0.0360.0420.67 0.065 ± 0.1180.0830.55 0.055 ± 0.0720.030.76 0.073 ± 0.0810.0140.90 0.0070.88 0.5580.00 ΔTC (mg·dL–1)–1.5 ± 19.60.7960.08 2.9 ± 18.30.5930.16 –0.3 ± 10.10.9310.03 1.2 ± 16.70.8190.07 0.7860.16 0.9420.08 Δ Ln HDL-C (mg·dL–1)a0.013 ± 0.1050.6790.12 0.083 ± 0.1180.0340.70 –0.044 ± 0.1030.1920.43 0.036 ± 0.0930.2280.39 0.0030.96 0.2910.00 Δ Ln TG (mg·dL–1)a–0.005 ± 0.2670.9520.02 –0.163 ± 0.4210.2080.39 –0.074 ± 0.4370.5830.17 –0.122 ± 0.2380.1190.51 0.2090.44 0.4240.16 ΔLDL-C (mg·dL–1)–2.4 ± 210.6980.11 4.1 ± 230.5460.18 6 ± 15.60.2290.38 3.3 ± 14.60.4770.23 0.6780.20 0.4120.29 Δ Ln FPI (μU·mL–1)a–0.079 ± 0.2530.3060.31 0.001 ± 0.3770.9950.00 0.082 ± 0.3910.5050.16 0.055 ± 0.3810.6430.01 0.9260.09 0.5020.18 Δ Ln FPG (mg·dL–1)a–0.044 ± 0.0860.1060.51 –0.007 ± 0.0650.7290.11 0.003 ± 0.0490.860.06 0.005 ± 0.0690.8310.07 0.4160.33 0.3650.31 Δ Ln HOMA-IRa–0.122 ± 0.2550.1260.48 –0.006 ± 0.3870.9590.02 0.084 ± 0.4110.5130.20 0.059 ± 0.4250.6530.14 0.8160.14 0.3220.34 Δ Ln TBARS (μmol·L–1) a–0.006 ± 0.090.820.07 –0.071 ± 0.1230.0710.58 –0.059 ± 0.1110.1120.53 –0.085 ± 0.1240.0470.69 0.0110.71 0.2080.30 Short-bouts = three 10-min exercises d–1 on 3 d week–1;
Long-bout = 30-min exercises d–1 on 3 d weeks–1. SBP: systolic
blood pressure, DBP: diastolic blood pressure, PR; pulse rate, BW: body weight, BMI:
body mass index, V·O2max: maximum oxygen uptake, TC: total cholesterol,
HDL-C: high-density lipoprotein cholesterol, TG: triglyceride, LDL-C: low-density
lipoprotein cholesterol, FPI: fasting plasma insulin, FPG: fasting plasma glucose,
HOMA-IR: Homeostasis model assessment of insulin resistance, TBARS: thiobarbituric
acid reactive substances, ES: effect size (these values represent as absolute values).
The thresholds for small, medium, and large effects were defined as d
values below 0.20, 0.50, and 0.80; f values below 0.10, 0.25, and
0.40; and f 2 values below 0.02, 0.15, and 0.35,
respectively. a: for analyses there values were log-transformed. b: p
for paired t-test, versus baseline. c: p for
MANOVA.). The Short-bouts
group demonstrated significant increases in VO2max after 10 weeks and in HDL-C
after 20 weeks, whereas the DBP after both 10 and 20 wk and the SBP after 20 wk had
significantly increased (Table 2). The
VO2max after 20 wk showed a trend toward an increase in the Short-bouts
group, with a medium ES (d=0.55), but this change did not reach
statistical significance (p=0.08). Physical fitness levels increased with
both multiple short bouts (2.4 ml·kg−1·min−1, 7.0%) and a single
long bout (2.7 ml·kg−1·min−1, 7.1%) of exercise. Plasma levels of
TBARS significantly decreased after 20 wk in the Long-bout group (Table 2). A trend towards decreased plasma levels of TBARS with
a medium ES (d=0.58) was observed after 20 wk in the Short-bouts group
but did not reach statistical significance (p=0.07).  As shown in Table 2, comparison [p (time ×
group)] between the long and short bouts of exercise showed no significant difference in
the effects of the interventions on the overall variables. Moreover, the ES (f
2) values for VO2max, TC, and HDL-C were also below the
medium level (0.15). Waist circumference, HDL-C, VO2max, and TBARS
significantly improved in all subjects over the 20 wk, whereas diastolic blood pressure
significantly increased [p (time) in Table 2].

BODY.DISCUSSION:
This study highlights 2 major findings in sedentary male Japanese workers. First, the
results of this study demonstrated no significant differences in cardiorespiratory fitness,
anthropometry, or the lipid profile between accumulated short bouts of exercise and single
long bouts of exercise even over a long-term intervention. Second, the subjects overall
showed a significant reduction in oxidative stress during the exercise programs, and no
significant difference in these effects was observed between the exercise programs. These
findings suggest that accumulation of total exercise duration per week is more important
than the length of each exercise session and thus provide an alternative for busy
workers.

BODY.DISCUSSION.EFFECT ON PHYSICAL FITNESS:
High levels of physical fitness have been shown to reduce the risks of cardiovascular
disease, diabetes mellitus, and some types of cancer in male Japanese workers26,27,28). Therefore, it is important for occupational health to
promote physical fitness among workers to prevent in-office deaths and decreased
productivity due to these diseases29,30,31). The present study demonstrated that physical fitness
levels, as indicated by VO2max, increased in response to both short bouts (2.4
ml·kg−1·min−1, 7.0%, p=0.08,
d=0.55 [a medium ES]) and long bouts (2.7
ml·kg−1·min−1, 7.1%, p=0.01,
d=0.90 [a large ES]) of exercise. In a long-term intervention study by
Jakicic, et al., physical fitness levels in overweight women increased by 6.3% and 9.9%
after 72 wk of short-bouts or long-bout exercise, respectively, with no difference between
the exercise groups7).
Recently, Osei-Tutu et al., reported that physical fitness levels
increased by 7.2% in the Short-bouts group and by 6.7% in the Long-bout group in studies
conducted over 8 weeks in sedentary men10). The results of the present study investigating the
improvements in physical fitness over 20 wk in sedentary male workers are consistent with
those of these previous studies.  On the other hand, a previous study reported that physical fitness in sedentary healthy
men who jogged for 30 min/d on 5 days per week for 8 wk increased by 7.6% in a Short-bouts
group and 13.9% in a Long-bout group, a significantly greater increase in the Long-bout
group6). Murphy et
al., have shown improvements in physical fitness in response to either 3 short
bouts (14.2%) or 1 long bout (3.8%) of brisk walking for 10 weeks in sedentary women, but
this increase was greater in the group walking for short bouts8). These differences may be due to the exercise
intensities used in each study. For example, the exercise intensities (>70% maximum
heart rate) in the studies cited above were higher than the intensity used in the current
study (50% of maximal oxygen consumption, ≤70% maximum heart rate). Further study is
needed to clarify the effects of the mode and intensity of exercise on physical
fitness.

BODY.DISCUSSION.EFFECTS ON FAT DISTRIBUTION, LIPID PROFILE, AND OTHER CARDIOVASCULAR RISK
FACTORS:
The Long-bout group demonstrated a significant decrease in waist circumference after 20
wk compared with the baseline value, but the decrease in waist circumference in the
Short-bouts group showed a small ES (d=0.40) and did not reach statistical significance.
BMI was unaltered in both groups. The decreases in waist circumference in the Long-bout
group could indicate a potential alteration in the distribution of body fat away from the
waist, which may lower the risk of cardiovascular disease. An interventional study by
Osei-Tutu et al., also reported that only long-bout walking produced
significant reductions in the percentage of body fat10). However, there are some reports that exercise patterns
do not influence the magnitudes of anthropometric changes7,8,9). These inconsistencies may be attributed to population
differences in parameters such as the pre-intervention waist circumference.  The Short-bouts group in the current study demonstrated a significant increase in the
HDL-C level after 20 wk, but the HDL-C level in the Long-bout group showed a small ES
(d=0.39) and was not significantly different. Increases in HDL-C may
reduce cardiovascular risk. However, findings from other studies vary regarding the
effects of brisk walking (whether accumulated through short bouts or through longer
sessions) on serum lipid levels. While some studies report changes in response to both
patterns of exercise9), others
do not32). These
inconsistencies may also be attributed to population differences in parameters such as the
pre-intervention lipid profile12).  No changes in other cardiovascular risk factors (TC, TG, LDL-C, or glucose metabolism)
were observed in the 2 exercise groups in this study. Eriksen and colleagues have reported
that short bouts of exercise are preferable to a single continuous exercise period with
regard to their effects on glucose metabolism32), but the intensity of exercise in that study (60% to 65%
of maximal oxygen consumption) was higher than that used in the current study, suggesting
that this difference in exercise intensity might explain the inconsistencies.

BODY.DISCUSSION.EFFECT ON OXIDATIVE STRESS:
The current study showed almost identical reductions in plasma levels of TBARS between
the exercise groups over the 20-wk study period, based on the findings of no significant
difference in the effects of the interventions when the long and short bouts of exercise
were compared and on significant improvements in plasma levels of TBARS in all subjects
over the 20 wk. The plasma levels of TBARS after 20 wk tended to be lower in the
short-bouts group; although this trend did not reach statistical significance
(p=0.07), the ES was medium (d=0.58), suggesting
possible practical implications. Despite other studies that have reported the efficacy of
1 continuous exercise period33,
34), to our
knowledge, no other studies have examined whether the total accumulated exercise duration
could suppress oxidative stress. Oxidative stress is closely associated with the
pathogenesis and the progression of cardiovascular risk factors13,14,15,16). Thus, from the perspective of occupational health for busy
workers, it is highly significant that the total accumulated exercise duration may limit
cardiovascular risk through the reduction of oxidative stress.

BODY.DISCUSSION.STRENGTH AND LIMITATIONS:
This study has several strengths. First, this was a randomized controlled study. Second,
the subjects of this study were middle-aged male Japanese workers. There have been few
studies that focused on the comparison between short and long bouts of exercise using data
from Japanese workers. Third, the exercise programs used in this study were tailor-made
exercise programs of moderate intensity, which was measured objectively by the cycle
ergometer. However, this study also has several limitations. First, this study did not
have a control group despite the random assignment of the interventional groups. The aim
of this study was to compare the effects of short-bout and long-bout exercise on
cardiovascular risk factors, and a single continuous exercise session lasting 30 min is
generally recognized as a non-pharmacologic therapy for lifestyle-related diseases.
Therefore, in this study, the Long-bout group was considered the control group. Second, in
the Short-bouts group, a significant increase in blood pressure in comparison with
baseline was observed after 20 wk. This interventional study began in June, and the
laboratory follow-ups were held in September (after 10 wk) and December (after 20 wk).
Blood pressure is known to vary with the time of year, and the odds ratio for a systolic
blood pressure ≥ 120 mm Hg is 1.24 for winter versus summer months35). Such seasonal changes in blood
pressure may explain the unexpected increase associated with short bouts of exercise.
However, the blood pressure levels in the Long-bout group were unchanged, suggesting a
suppressive effect of continuous exercise on the seasonal increase in blood pressure.
Third, this study is limited by the relatively small sample size. A larger sample would be
necessary to establish full equivalence between the effects of 3 short bouts of exercise
and 1 longer bout of exercise36,
37). Moreover, all
of the ES (f 2) values in Table 2 except those for VO2max, TC, and HDL-C were either large or
medium. Therefore, based on the results of the current study, exercise in short bouts
cannot be deemed as effective as long-bout exercise. Finally, the rates of adherence to
the prescribed exercise programs were 60% to 70%, but there was no dropout. Low exercise
compliance may explain the small effects of exercise on cardiovascular risk factors,
including the smaller-than-expected improvements in lipid profiles and glucose metabolism.
Moreover, the adherence rate in the Short-bouts group was unexpectedly lower than that in
the Long-bout group, although the difference was not significant. Because the participants
in this study included researchers from the university who make frequent business trips,
it may have been difficult to practically implement the short-bouts exercise program using
a fixed cycle ergometer. These results also imply that occupational practitioners should
match the exercise program, either short or long bouts of exercise, to the participant's
work-style.

BODY.CONCLUSIONS:
We have demonstrated in this study that it is the performance of an exercise program itself
rather than the exact nature of the program that is effective for improving physical
fitness, the lipid profile, and oxidative stress and that short-bout exercise protocols are
an option, especially for busy workers, for incorporating exercise into one's lifestyle. A
larger-scale randomized controlled test should be planned to determine the equivalence
between the effects of 3 short bouts of exercise versus 1 longer bout of exercise.

Question: Compared to baseline what was the result of performed a single period of continuous exercise (Long-bout group: 30 min × 1) 3 d per week, on lasma levels of TBARS (thiobarbituric acid-reactive substances)?
Evidence: Plasma levels of
TBARS significantly decreased after 20 wk in the Long-bout group (Table 2). 
Answer: significantly decreased