{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T13:07:48Z","timestamp":1775567268348,"version":"3.50.1"},"reference-count":35,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T00:00:00Z","timestamp":1775520000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Bioengineering"],"abstract":"<jats:p>Background: The Global Positioning System (GPS) and wearable monitoring technologies are increasingly applied in sport science to quantify training load; however, data from female cross-country skiers in nations with emerging competitive programs remain scarce. This case series covering the complete national team roster analyzed the complete annual training cycle of the Korean women\u2019s national cross-country skiing team (KCF) using GPS and heart rate-based wearable sensors. Methods: All three national team members were monitored throughout the 2022\u20132023 season (52 weeks), structured into General Preparation Period 1 (April\u2013July), General Preparation Period 2 (August\u2013November), and Competition Period (December\u2013March). Individualized five-zone intensity thresholds were established through graded exercise testing on a roller ski treadmill with ventilatory threshold and blood lactate determination, independently assessed by two exercise physiologists (PhD level). Results: The total annual training volume was 667.72 h, comprising roller\/on-snow skiing (54.0%), running (23.3%), and strength training (22.7%). The endurance-only intensity distribution demonstrated a polarized pattern (Zones 1\u20132: 91.5%). The total annual training distance reached 4673.30 km. The mean FIS points were 108.46 \u00b1 38.60, and the mean VO2max was 60.17 \u00b1 6.11 mL\u00b7kg\u22121\u00b7min\u22121. Conclusions: When benchmarked against world-class female (WCF) standards (800\u2013950 h annually), the overall training volume was approximately 18\u201330% lower. The relative strength training allocation (22.7%) exceeded typical WCF values (10\u201315%). These observations should be interpreted cautiously given the small sample size and cross-study comparison design, using published literature-based benchmarks.<\/jats:p>","DOI":"10.3390\/bioengineering13040429","type":"journal-article","created":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T12:03:47Z","timestamp":1775563427000},"page":"429","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Quantitative Analysis of Annual Training Volume and Periodization Patterns in Elite Female Cross-Country Skiers Using GPS Monitoring: A Three-Athlete Case Study"],"prefix":"10.3390","volume":"13","author":[{"given":"Xiangzi","family":"Xiao","sequence":"first","affiliation":[{"name":"Department of Education, Taylor\u2019s University, Jalan Taylor\u2019s, Subang Jaya 47500, Malaysia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Soyoun","family":"Moon","sequence":"additional","affiliation":[{"name":"Department of Physical Education, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1327-8998","authenticated-orcid":false,"given":"Yonghwan","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Physical Education, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea"},{"name":"Laboratory of Integrative Physiology, Department of Health and Human Performance, University of Houston, Houston, TX 77204, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3543-6301","authenticated-orcid":false,"given":"Yongchul","family":"Choi","sequence":"additional","affiliation":[{"name":"Department of Physical Education, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1003","DOI":"10.1123\/ijspp.2016-0749","article-title":"Physiological capacity and training routines of elite cross-country skiers: Approaching the upper limits of human endurance","volume":"12","author":"Sandbakk","year":"2017","journal-title":"Int. J. Sports Physiol. Perform."},{"key":"ref_2","first-page":"1072","article-title":"Aerobic-Resistance Exercise Improves Double Pole Performance and Kinematics in Harder Conditions in Junior Cross-Country Skiers","volume":"39","author":"Feofilaktov","year":"2025","journal-title":"J. Strength Cond. Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"353","DOI":"10.1152\/jappl.1967.23.3.353","article-title":"Maximal oxygen uptake in athletes","volume":"23","author":"Saltin","year":"1967","journal-title":"J. Appl. Physiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1111\/j.1600-0838.1991.tb00267.x","article-title":"Maximal oxygen uptake as a predictor of performance ability in women and men elite cross-country skiers","volume":"1","author":"Ingjer","year":"1991","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e101796","DOI":"10.1371\/journal.pone.0101796","article-title":"The road to gold: Training and peaking characteristics in the year prior to a gold medal endurance performance","volume":"9","author":"Sylta","year":"2014","journal-title":"PLoS ONE"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1111\/j.1600-0838.2004.00418.x","article-title":"Quantifying training intensity distribution in elite endurance athletes: Is there evidence for an \u201coptimal\u201d distribution?","volume":"16","author":"Seiler","year":"2006","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"276","DOI":"10.1123\/ijspp.5.3.276","article-title":"What is best practice for training intensity and duration distribution in endurance athletes?","volume":"5","author":"Seiler","year":"2010","journal-title":"Int. J. Sports Physiol. Perform."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"315466","DOI":"10.3389\/fphys.2017.01069","article-title":"The training characteristics of the world\u2019s most successful female cross-country skier","volume":"8","author":"Solli","year":"2017","journal-title":"Front. Physiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1519\/00126548-200312000-00005","article-title":"Periodization strategies","volume":"25","author":"Plisk","year":"2003","journal-title":"Strength Cond. J."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"189","DOI":"10.2165\/11319770-000000000-00000","article-title":"New horizons for the methodology and physiology of training periodization","volume":"40","author":"Issurin","year":"2010","journal-title":"Sports Med."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"490.e1","DOI":"10.1016\/j.scispo.2021.09.004","article-title":"Physiological profiles and training loads of international level male and female cross-country skiers and biathletes","volume":"37","author":"Myakinchenko","year":"2022","journal-title":"Sci. Sports"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"e70067","DOI":"10.1002\/ejsc.70067","article-title":"Block Training with Moderate-or High-Intensity Intervals Both Improve Endurance Performance in Well-Trained Cyclists","volume":"25","author":"Odden","year":"2025","journal-title":"Eur. J. Sport Sci."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Solli, G.S., T\u00f8nnessen, E., and Sandbakk, \u00d8. (2019). Block vs. Traditional Periodization of HIT: Two Different Paths to Success for the World\u2019s Best Cross-Country Skier. Front. Physiol., 10.","DOI":"10.3389\/fphys.2019.00375"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1181","DOI":"10.1123\/ijspp.2019-0220","article-title":"The annual periodization of training volumes of international-level cross-country skiers and biathletes","volume":"15","author":"Myakinchenko","year":"2020","journal-title":"Int. J. Sports Physiol. Perform."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1111\/j.1600-0838.2012.01482.x","article-title":"Gender differences in endurance performance by elite cross-country skiers are influenced by the contribution from poling","volume":"24","author":"Sandbakk","year":"2014","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref_16","first-page":"465","article-title":"The effect of 3 weeks high altitude skiing training on isokinetic muscle function of cross-country skierst","volume":"9","author":"Choi","year":"2018","journal-title":"J. Korea Converg. Soc."},{"key":"ref_17","first-page":"993","article-title":"The Study of Sprint Cardiorespiratory Index and Body Composition according to Period in National and Reserve Cross-country Skier","volume":"27","author":"Choi","year":"2018","journal-title":"Korean Soc. Sports Sci."},{"key":"ref_18","first-page":"1313","article-title":"Effects of high altitude training on maximal exercise capacity, RBC, and Hb concentration in cross-country skier","volume":"22","author":"Kim","year":"2013","journal-title":"Korea J. Sports Sci."},{"key":"ref_19","first-page":"659","article-title":"Effects of Living Low and Training High on Body Composition, Exercise Performance, Blood CK, Lactate and Oxidative Stress Makers Responses in Cross Country Skiers","volume":"53","author":"Lee","year":"2013","journal-title":"J. Sports Leis. Stud."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1091","DOI":"10.1249\/MSS.0000000000000862","article-title":"The physiological capacity of the world\u2019s highest ranked female cross-country skiers","volume":"48","author":"Sandbakk","year":"2016","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1007\/s00421-021-04802-5","article-title":"Analysis of sex-based differences in energy substrate utilization during moderate-intensity aerobic exercise","volume":"122","author":"Cano","year":"2022","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Julian, R., Hecksteden, A., Fullagar, H.H., and Meyer, T. (2017). The effects of menstrual cycle phase on physical performance in female soccer players. PLoS ONE, 12.","DOI":"10.1371\/journal.pone.0173951"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2007","DOI":"10.1113\/EP088548","article-title":"Physiological sex differences affect the integrative response to exercise: Acute and chronic implications","volume":"105","author":"Ansdell","year":"2020","journal-title":"Exp. Physiol."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Casta\u00f1eda-Babarro, A., Etayo-Urtasun, P., and Le\u00f3n-Guere\u00f1o, P. (2022). Effects of strength training on cross-country skiing performance: A systematic review. Int. J. Environ. Res. Public Health, 19.","DOI":"10.3390\/ijerph19116522"},{"key":"ref_25","unstructured":"Committee, I.O. (2026, February 01). Cross-Country Skiing at Milano Cortina 2026: For the First Time in History, Men and Women Race over the Same Distances. Available online: https:\/\/www.olympics.com."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"295","DOI":"10.1123\/ijspp.6.3.295","article-title":"Applications of GPS technologies to field sports","volume":"6","author":"Aughey","year":"2011","journal-title":"Int. J. Sports Physiol. Perform."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1123\/ijspp.2023-0067","article-title":"Annual volume and distribution of physical training in Norwegian female cross-country skiers and biathletes: A comparison between sports, competition levels, and age categories\u2014The FENDURA project","volume":"19","author":"Osborne","year":"2023","journal-title":"Int. J. Sports Physiol. Perform."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"555","DOI":"10.1080\/02640414.2025.2468585","article-title":"The reliability of a commonly used (CatapultTM Vector S7) microtechnology unit to detect movement characteristics used in court-based sports","volume":"43","author":"Mackay","year":"2025","journal-title":"J. Sports Sci."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Schaffarczyk, M., Rogers, B., Reer, R., and Gronwald, T. (2022). Validity of the polar H10 sensor for heart rate variability analysis during resting state and incremental exercise in recreational men and women. Sensors, 22.","DOI":"10.3390\/s22176536"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Walther, J., Haugen, T., Solli, G.S., T\u00f8nnessen, E., and Sandbakk, \u00d8. (2023). From juniors to seniors: Changes in training characteristics and aerobic power in 17 world-class cross-country skiers. Front. Physiol., 14.","DOI":"10.3389\/fphys.2023.1288606"},{"key":"ref_31","first-page":"2127","article-title":"Methodological quality of case series studies: An introduction to the JBI critical appraisal tool","volume":"18","author":"Munn","year":"2020","journal-title":"JBI Evid. Synth."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1450","DOI":"10.1152\/japplphysiol.00714.2014","article-title":"Individual response to exercise training\u2014A statistical perspective","volume":"118","author":"Hecksteden","year":"2015","journal-title":"J. Appl. Physiol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1113\/jphysiol.2007.143834","article-title":"Endurance exercise performance: The physiology of champions","volume":"586","author":"Joyner","year":"2008","journal-title":"J. Physiol."},{"key":"ref_34","first-page":"155","article-title":"Practical implementation of strength training to improve the performance of world-class cross-country skiers","volume":"50","author":"Sandbakk","year":"2018","journal-title":"Kinesiology"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"603","DOI":"10.1111\/sms.12104","article-title":"Optimizing strength training for running and cycling endurance performance: A review","volume":"24","author":"Mujika","year":"2014","journal-title":"Scand. J. Med. Sci. Sports"}],"container-title":["Bioengineering"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2306-5354\/13\/4\/429\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T12:33:55Z","timestamp":1775565235000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2306-5354\/13\/4\/429"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,7]]},"references-count":35,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["bioengineering13040429"],"URL":"https:\/\/doi.org\/10.3390\/bioengineering13040429","relation":{},"ISSN":["2306-5354"],"issn-type":[{"value":"2306-5354","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,7]]}}}