{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,3]],"date-time":"2026-03-03T02:02:53Z","timestamp":1772503373950,"version":"3.50.1"},"reference-count":49,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,2,20]],"date-time":"2021-02-20T00:00:00Z","timestamp":1613779200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>This study aimed to describe habitual sleep and nocturnal cardiac autonomic activity (CAA), and their relationship with training\/match load in male youth soccer players during an international tournament. Eighteen elite male youth soccer players (aged 14.8 \u00b1 0.3 years; mean \u00b1 SD) participated in the study. Sleep indices were measured using wrist actigraphy, and heart rate (HR) monitors were used to measure CAA during night-sleep throughout 5 consecutive days. Training and match loads were characterized using the session-rating of perceived exertion (s-RPE). During the five nights 8 to 17 players slept less than &lt;8 h and only one to two players had a sleep efficiency &lt;75%. Players\u2019 sleep duration coefficient of variation (CV) ranged between 4 and 17%. Nocturnal heart rate variability (HRV) indices for the time-domain analyses ranged from 3.8 (95% confidence interval, 3.6; 4.0) to 4.1 ln[ms] (3.9; 4.3) and for the frequency-domain analyses ranged from 5.9 (5.6; 6.5) to 6.6 (6.3; 7.4). Time-domain HRV CV ranged from 3 to 10% and frequency-domain HRV ranged from 2 to 12%. A moderate within-subjects correlation was found between s-RPE and sleep duration [r = \u22120.41 (\u22120.62; \u22120.14); p = 0.003]. The present findings suggest that youth soccer players slept less than the recommended during the international tournament, and sleep duration was negatively associated with training\/match load.<\/jats:p>","DOI":"10.3390\/ijerph18042076","type":"journal-article","created":{"date-parts":[[2021,2,20]],"date-time":"2021-02-20T13:17:02Z","timestamp":1613827022000},"page":"2076","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Sleep Indices and Cardiac Autonomic Activity Responses during an International Tournament in a Youth National Soccer Team"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5515-3694","authenticated-orcid":false,"given":"Pedro","family":"Figueiredo","sequence":"first","affiliation":[{"name":"Portugal Football School, Portuguese Football Federation, FPF, 1495-433 Cruz Quebrada, Portugal"},{"name":"Research Center in Sports Sciences, Health Sciences and Human Development, CIDESD, University Institute of Maia, ISMAI, 4475-690 Maia, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8225-8667","authenticated-orcid":false,"given":"J\u00falio","family":"Costa","sequence":"additional","affiliation":[{"name":"Portugal Football School, Portuguese Football Federation, FPF, 1495-433 Cruz Quebrada, Portugal"},{"name":"Center of Research, Education, Innovation and Intervention in Sport, CIFI2D, Faculty of Sport, University of Porto, 4200-450 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1793-3811","authenticated-orcid":false,"given":"Michele","family":"Lastella","sequence":"additional","affiliation":[{"name":"Appleton Institute for Behavioural Science, Central Queensland University, Adelaide, QLD 5034, Australia"}]},{"given":"Jo\u00e3o","family":"Morais","sequence":"additional","affiliation":[{"name":"Portugal Football School, Portuguese Football Federation, FPF, 1495-433 Cruz Quebrada, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1301-1078","authenticated-orcid":false,"given":"Jo\u00e3o","family":"Brito","sequence":"additional","affiliation":[{"name":"Portugal Football School, Portuguese Football Federation, FPF, 1495-433 Cruz Quebrada, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1487","DOI":"10.1007\/s40279-019-01119-4","article-title":"Sleep Monitoring in Athletes: Motivation, Methods, Miscalculations and Why it Matters","volume":"49","author":"Halson","year":"2019","journal-title":"Sports Med."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"6","DOI":"10.1016\/j.sleh.2016.11.006","article-title":"National Sleep Foundation\u2019s sleep quality recommendations: First report","volume":"3","author":"Ohayon","year":"2017","journal-title":"Sleep Healyh"},{"key":"ref_3","first-page":"843","article-title":"Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society","volume":"38","author":"Watson","year":"2015","journal-title":"Sleep"},{"key":"ref_4","unstructured":"Sawczuk, T., Jones, B., Scantlebury, S., and Till, K. 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