{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T12:10:36Z","timestamp":1784203836360,"version":"3.55.0"},"reference-count":46,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T00:00:00Z","timestamp":1783900800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Physiol."],"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To determine the optimal weekly frequency of 4 \u00d7 4\u00a0min high\u2212intensity interval training (HIIT) in male university students and thus provide evidence for prescribing efficient endurance training in this population.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      Forty\u2212five physically active male university students were randomly assigned to three groups performing 4 \u00d7 4\u00a0min HIIT once, twice, or three sessions per week (n = 15 per group) for 6 weeks. Maximal oxygen uptake (VO\n                      <jats:sub>2<\/jats:sub>\n                      max), time to exhaustion, heart rate (HR), oxygen uptake (VO\n                      <jats:sub>2<\/jats:sub>\n                      ), ventilatory threshold (VT), respiratory exchange ratio (RER), and blood lactate concentration were assessed via treadmill testing and breath\u2212by\u2212breath gas analysis. Repeated\u2212measures ANOVA was used for statistical analysis.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      After 6 weeks of intervention, all groups showed prolonged time to exhaustion and reduced submaximal HR and blood lactate, with the 2\u2212 and 3\u2212session groups exhibiting larger improvement magnitudes. VO\n                      <jats:sub>2<\/jats:sub>\n                      max increased markedly in both the 2\u2212 and 3\u2212session groups, while the 1\u2212session group showed only a small increase. Submaximal VO\n                      <jats:sub>2<\/jats:sub>\n                      , VT, and RER changed minimally across groups. Post\u2212intervention blood lactate was notably lower in the 2\u2212 and 3\u2212session groups than in the 1\u2212session group (p &amp;lt; 0.001), whereas physiological improvements were generally comparable between the 2\u2212 and 3\u2212session groups. Training completion rates were 100%, 93%, and 80% in the 1\u2212, 2\u2212, and 3\u2212session groups, respectively.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Within the present study conditions, twice\u2212weekly 4 \u00d7 4\u00a0min HIIT yielded substantial improvements in aerobic capacity and submaximal metabolic economy while maintaining relatively high adherence, showing a favorable balance between training benefits and tolerability. The twice\u2212weekly frequency appears relatively optimal for physically active male university students. These findings are limited by the homogeneous sample and short intervention period, and further validation in larger, diverse cohorts is warranted.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fphys.2026.1855612","type":"journal-article","created":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T04:23:02Z","timestamp":1783916582000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Study on the effects of 4 \u00d7 4\u00a0min high\u2212intensity interval training frequency on cardiorespiratory function, metabolic indices, and exercise performance in male university students"],"prefix":"10.3389","volume":"17","author":[{"given":"Hanwen","family":"Zhang","sequence":"first","affiliation":[{"name":"Capital University of Physical Education and Sports","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yingjian","family":"Zhang","sequence":"additional","affiliation":[{"name":"Langfang Normal University","place":["Langfang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Heng","family":"Tian","sequence":"additional","affiliation":[{"name":"Qufu Normal University","place":["Qufu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yang","family":"Gao","sequence":"additional","affiliation":[{"name":"Army Engineering University of PLA","place":["Xuzhou, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mingxi","family":"Zhang","sequence":"additional","affiliation":[{"name":"Hebei Sport University","place":["Shijiazhuang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,7,13]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0073182","article-title":"VO2max trainability and high intensity interval training in humans: a meta-analysis","volume":"8","author":"Bacon","year":"2013","journal-title":"PLoS One"},{"key":"B2","doi-asserted-by":"publisher","first-page":"494","DOI":"10.1136\/bjsports-2015-095841","article-title":"Effects of high-intensity interval training on cardiometabolic health: a systematic review and meta-analysis of intervention studies","volume":"51","author":"Batacan","year":"2017","journal-title":"Br. 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