What the answer rests on. One randomized three-group trial of healthy adults aged 44 to 78 in Japan (Nemoto and colleagues, 2007), analysed per protocol, carries the comparison with steady walking. Four more studies add the dose (Masuki and colleagues, 2019), 22-month adherence (Masuki and colleagues, 2015), a test outside Japan (Lalande and colleagues, 2010) and a test in young women (Tanabe and colleagues, 2018), and a 2024 review written with the method's developers (Karstoft and colleagues) adds context. Three meta-analyses of other training (Guo and colleagues, 2023; Fosstveit and colleagues, 2024; Azimkhani and colleagues, 2026) are frame only; none studied interval walking. Every interval-walking fitness and strength result here comes from the Shinshu University laboratory that designed interval walking training or from a trial run with it. Targeted searches during FitChef's research found no interval-walking trial independent of that laboratory that measured fitness or strength in healthy adults; the one outside randomized trial of interval walking found measured outcomes outside this page's scope. Two of the six sources (Masuki 2019 and Tanabe 2018) were read as abstracts only.
The three-group trial. Nemoto, Gen-no, Masuki, Okazaki and Nose (Shinshu University), Mayo Clin Proc 2007;82(7):803-811, DOI 10.4065/82.7.803, PMID 17605959. From May to October 2004, 246 healthy, nonsmoking adults aged 44 to 78 (mean 63; 60 men, 186 women) were randomly divided into no training, steady walking and interval walking, with minor reassignments for married couples and for people living far from the administrative center. Steady walkers were asked to walk at about 50% of their peak aerobic capacity for walking, with a pedometer confirming 8,000 or more steps a day, on 4 or more days a week. Interval walkers were asked to repeat 5 or more sets of a 3-minute fast walk (above 70% and below 85% of their own peak capacity for walking) and 2 to 3 minutes slow (about 40%) on 4 or more days a week. Knee extension and flexion force were measured with a dynamometer; peak aerobic capacity for cycling by expired gas analysis, and for walking from a back-worn accelerometer's readings converted to oxygen consumption with an equation.
Its results. The analysis is per protocol, with no intention-to-treat analysis: 9 men and 37 women (55%) without training, 8 men and 43 women (68%) steady, and 11 men and 31 women (48%) interval met the inclusion criteria, and the authors write that the findings may be influenced by selection bias. In the interval group, knee extension force rose 13%, knee flexion force 17%, peak aerobic capacity for cycling 8% and for walking 9% (all P<.001), each significantly greater than the steady group's increase (all P<.01). Steady walking did not differ significantly from no training on any variable except one outside this page's scope; within the steady group, women's knee flexion force rose from 45 to 48 N·m (P<.01 against their starting value; Table 4). Table 1 (per protocol): interval walkers walked 55 (men) and 51 (women) minutes a day, 35 and 32 of them fast, against 66 and 61 minutes for the steady walkers; daily energy expenditure (mL O2 per day: 54,656 and 37,880 for the steady men and women who carried an accelerometer, 54,542 and 41,003 for the interval men and women) did not differ significantly between the walking groups (P=.66), and the interval walkers' walking time was 83% of the steady group's. Weight: women in both walking groups lost a little (interval 53.7 to 52.9 kg, steady 54.4 to 53.2 kg) while no-training women gained (54.1 to 54.9 kg); no men's weight change was significant, and the paper does not report the interval walkers losing more than the steady walkers.
Support and monitoring differed. Interval walkers learned the regimen in small groups during the first month, wore a back-mounted accelerometer that beeped at each scheduled change of pace, and visited a local office every 2 weeks, where their device data went to a central server and trainers used the reports to instruct them, encouraging anyone below target. Steady walkers used pedometers and visited the administrative center once a month for a compliance review; 18 of them (6 men, 12 women) also carried the accelerometer. The interval group visited about 18 times against about 11 and interacted with the trainer more; the authors write that they believe it is unlikely these differences affected the main outcomes. After training, 30% (no training), 17% (steady) and 22% (interval) did not return for testing, and a further 15%, 15% and 30% did not meet the inclusion criteria. Funding: grants from Japan's Ministry of Health, Labor, and Welfare, the Japan Society for Promotion of Science and the Ministry of Economy, Trade, and Industry; no industry funder is named, and no conflict-of-interest statement appears in the text FitChef worked from.
Fast minutes and the gain. Masuki, Morikawa and Nose, Mayo Clin Proc 2019;94(12):2415-2426, DOI 10.1016/j.mayocp.2019.04.039, PMID 31477320 (abstract only; the full text is subscription-only and was not read). 679 men and women (mean age 65 ± 7) completed 5 months of the same regimen between April 2005 and February 2008, walking 88 ± 65 fast and 100 ± 86 slow minutes a week on average, with wide variation. Participants were grouped into bins of weekly fast and slow walking time: estimated peak aerobic capacity improved as weekly fast walking time rose up to 50 minutes and plateaued above that, with R2 = 0.94 describing the fit of the bin averages, not of individuals; its improvement was not positively correlated with slow or total walking time, and multiple regression identified fast walking time as the major determinant. The average gain was 14% in estimated peak aerobic capacity, in a single group with no control. Crossref lists Shinshu University, Japan's Ministry of Health, Labour and Welfare and the Japan Society for the Promotion of Science as funders; the abstract carries no conflict-of-interest statement.
Twenty-two months. Masuki, Mori, Tabara, Sakurai, Hashimoto, Morikawa, Miyagawa, Sumiyoshi, Miki, Higuchi and Nose, J Appl Physiol 2015;118(5):595-603 (published ahead of print 24 December 2014), DOI 10.1152/japplphysiol.00819.2014, PMID 25539937. 696 middle-aged and older adults (196 men, 500 women; age 65 ± 7) were recruited from a government-supported interval walking program in Matsumoto, Japan, and followed for 22 months with no sedentary control group. The regimen was 5 or more sets of 3 minutes at about 40% and 3 minutes at 70% or more but under 85% of peak capacity for walking on at least 4 days a week, paced by a waist accelerometer with beeping cues and reviewed with trainers every 2 weeks at a local office. Adherence, the walking days completed divided by those prescribed (4 a week), averaged 70 ± 1% (mean ± SE); on the days they walked, participants averaged 19.6 minutes of fast walking. Adherence fell over time in everyone and fell more with higher baseline BMI: the authors report 57, 53, 38 and 34% reductions after 22 months from the highest to the lowest BMI quartile. Baseline BMI was the major predictor (lower BMI, higher adherence), followed by sex (men 80 ± 3%, women 66 ± 2%) and age. Estimated peak aerobic capacity rose 2.6 ± 0.1 mL/kg/min (12%, P < 0.0001), most in those with the highest adherence and falling in those with the lowest; missing 22-month values were carried forward from month 17 or 10, and the authors note that their accelerometer estimate reads about 20% below maximal capacity measured by standard methods. Funding: a Shinshu University partnership project (with Matsumoto City among the partners) and Japanese government grants; no conflicts of interest declared.
Outside Japan, with a disclosure. Lalande, Okazaki, Yamazaki, Nose, Joyner and Johnson, J Prim Care Community Health 2010;1(2):104-110, DOI 10.1177/2150131910363598, PMID 23804371. At the Mayo Clinic in Rochester, Minnesota, 29 sedentary middle-aged adults (14 men; age 54 ± 8) started 3 months of interval walking and 26 finished (three women stopped with unrelated injuries); 17 adults matched for age, height, BMI and peak aerobic capacity (9 men; age 50 ± 6) did not train. The groups were not randomized, and changes were tested within each group. Walkers averaged 3.9 days a week, 34 minutes a session, 16 of them fast (131 minutes a week in all). Estimated peak aerobic capacity, from an accelerometer during a graded walking test, rose from 20.4 to 26.0 mL/kg/min (a 28 ± 25% change in Table 2; the results text says more than 25%) and did not change in the group that did not train; in that group the estimate correlated with gas analysis at r = .91. Weight, BMI, waist and hip fell slightly; body fat percentage did not change (from 33.1 to 32.4, P = 0.69), and diet was not assessed. The study was run with the Shinshu laboratory. Co-author Toshiaki Yamazaki is a manager of Kissei Comtec, maker of the accelerometer that paced the training and estimated the fitness result; the authors declared no conflicts of interest. Funding: Japan's Ministry of Health, Labor, and Welfare, the Japan Foundation for Aging and Health and the Uehara Memorial Foundation. Its size is not comparable with the other trials' results (different population, length and measures).
Younger women. Tanabe, Masuki, Nemoto and Nose, Int J Biometeorol 2018;62(4):643-654 (online 17 November 2017), DOI 10.1007/s00484-017-1473-3, PMID 29150762 (abstract only; funding not stated in the abstract). Sedentary female college students in Japan were randomly divided into home-based interval walking or control groups in summer (48 students aged 18 to 22, 176 days; 24 and 24) and in winter (47 aged 18 to 24, 133 days; 23 and 24). The daily peak temperature averaged 26 ± 6 °C in summer against 7 ± 5 °C in winter. In a vacation of about 50 days, summer walkers walked 2.1 days a week against 4.2 in winter (P < 0.001); both walking groups walked about 2 days a week in the school period. Peak aerobic capacity and knee flexion force rose in the winter walkers (P 0.3), and decreased in both summer groups; the authors conclude that adherence and effects fell in summer at least partially because of the high temperature. The abstract gives no effect sizes and does not describe the walking regimen.
The developers' review. Karstoft, Thorsen, Nielsen, Solomon, Masuki, Nose and Ried-Larsen, Appl Physiol Nutr Metab 2024;49(7):1002-1007, DOI 10.1139/apnm-2023-0595, PMID 38507778: a Perspective that reports no new data, co-written by the method's developers (Masuki and Nose) and Danish colleagues; unfunded. Declared interests: Solomon has consulted for Boost Treadmills, GU Energy and Examine.com and owns Blazon Scientific and Veohtu; Ried-Larsen has received a speaker fee from AstraZeneca and serves on an educational committee supported by the Novo Nordisk Foundation. Used here for four points: interval walking is of lower absolute intensity than high-intensity interval training and typically fully aerobic; the InterWalk app, developed in Denmark, set personal intensities from the phone's accelerometers and a 7-minute walking test, was downloaded 32,000 times in its first 2 years, and only a minority kept using it beyond the first download; volunteers for exercise studies are most likely more adherent than the general population; and the body-composition advantage it reports comes from the authors' own 4-month trial in people with type 2 diabetes. Its summaries of the Japanese trials differ in places from the primary papers, so this page uses the primary numbers.
Frame from other research. Fosstveit, Lohne-Seiler, Feron, Lucas, Ivarsson and Berntsen, Scand J Med Sci Sports 2024;34(2):e14573, DOI 10.1111/sms.14573: a meta-analysis of 23 randomized trials in 1,332 adults aged 60 and over, with no external funding, found no strong evidence that moderate- and high-intensity aerobic training differ in improving peak oxygen uptake once total exercise volume is taken into account. It did not study interval walking, and its intensity groups are not used to classify interval walking here. Guo, Li, Cai, Gong, Liu and Liu, Int J Environ Res Public Health 2023;20(6):4741, DOI 10.3390/ijerph20064741, PMID 36981649: a meta-analysis of 29 randomized trials (807 participants; inclusion 18 to 60 years; 20 of the 29 studies in people with sedentary obesity; most exercise forms cycling, and none of its interval programs was walking) found no statistical difference between high-intensity interval and moderate-intensity continuous training in body mass (MD −0.32 kg, p = 0.2514), BMI, fat mass (MD −0.22 kg, p = 0.5578) or fat-free mass. Interval training did better on waist circumference (MD −0.96 cm), percent fat mass (MD −0.48%) and VO2peak (SMD 0.19); in subgroups these differences appeared in the young and not in the middle-aged, and the authors judge the improvement so limited that whether it has more clinical meaning for fat loss and fitness is hard to say. Funding: National Social Science Fund of China; the authors declare no conflicts. Azimkhani, Kasraei, Sabeti and Almasoodi, Biol Res Nurs 2026;28(1):72-90, DOI 10.1177/10998004251348605, PMID 40501026: a meta-analysis of 51 randomized trials in 3,152 healthy adults aged 60 and over who were not already in structured exercise found that aerobic, resistance or combined training improved VO2max/peak against inactive comparison groups (SMD 0.51, 95% CI 0.38 to 0.65); programs of 24 weeks or less showed the larger pooled effect (SMD 0.67, against 0.20 beyond 24 weeks), a comparison between studies. The authors report considerable heterogeneity of protocols and a moderate to high risk of publication bias; no funding and no conflicts declared. Neither review studied interval walking: both are frame for the questions of fat loss and of fitness in later life, never findings about the method.
What no source here shows. For interval walking: that it burns more calories or fat than steady walking; any change in muscle size (strength was measured, muscle was not); results sooner than 3 months; results from a phone-timer version or from a prescribed version with fewer sets or days than the trials asked for; results in young men; or an independent replication of the fitness and strength results.
Effects of High-Intensity Interval Walking Training on Physical Fitness and Blood Pressure in Middle-Aged and Older People (Nemoto KI, Gen-no H, Masuki S, Okazaki K, Nose H. Mayo Clinic Proceedings, 2007) ·
DOI | High-Intensity Walking Time Is a Key Determinant to Increase Physical Fitness and Improve Health Outcomes After Interval Walking Training in Middle-Aged and Older People (Masuki S, Morikawa M, Nose H. Mayo Clinic Proceedings, 2019) ·
DOI | The factors affecting adherence to a long-term interval walking training program in middle-aged and older people (Masuki S, Mori M, Tabara Y, Sakurai A, Hashimoto S, Morikawa M, Miyagawa K, Sumiyoshi E, Miki T, Higuchi K, Nose H. Journal of Applied Physiology, 2015) ·
DOI | Effects of Interval Walking on Physical Fitness in Middle-Aged Individuals (Lalande S, Okazaki K, Yamazaki T, Nose H, Joyner MJ, Johnson BD. Journal of Primary Care & Community Health, 2010) ·
DOI | Seasonal influence on adherence to and effects of an interval walking training program on sedentary female college students in Japan (Tanabe A, Masuki S, Nemoto KI, Nose H. International Journal of Biometeorology, 2018) ·
DOI | Health benefits of interval walking training (Karstoft K, Thorsen IK, Nielsen JS, Solomon TPJ, Masuki S, Nose H, Ried-Larsen M. Applied Physiology, Nutrition, and Metabolism, 2024) ·
DOI | The intensity paradox: A systematic review and meta-analysis of its impact on the cardiorespiratory fitness of older adults (Fosstveit SH, Lohne-Seiler H, Feron J, Lucas SJE, Ivarsson A, Berntsen S. Scandinavian Journal of Medicine & Science in Sports, 2024) ·
DOI | Effect of High-Intensity Interval Training vs. Moderate-Intensity Continuous Training on Fat Loss and Cardiorespiratory Fitness in the Young and Middle-Aged a Systematic Review and Meta-Analysis (Guo Z, Li M, Cai J, Gong W, Liu Y, Liu Z. International Journal of Environmental Research and Public Health, 2023) ·
DOI | The Effect of Aerobic, Resistance, and Combined Exercise Training on Cardiorespiratory Fitness in Healthy People Aged 60 years and Over: A Systematic Review and Meta-Analysis of Randomized Controlled Trials (Azimkhani A, Kasraei R, Sabeti H, Almasoodi A. Biological Research for Nursing, 2026) ·
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