{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T16:01:15Z","timestamp":1790611275958,"version":"4.1.0"},"reference-count":28,"publisher":"PeerJ","license":[{"start":{"date-parts":[[2025,8,28]],"date-time":"2025-08-28T00:00:00Z","timestamp":1756339200000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>This study aims to assess the resistance level of beginner bodybuilders of mature and elderly age to strength training performed under anaerobic energy supply modes (creatine phosphokinase and glycolysis).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>The study involved 60 men who had been engaged in bodybuilding for only 12 months. Group A included men aged 24\u00a0\u00b1\u00a01.5 years (early mature age), group B consisted of men aged 40\u00a0\u00b1\u00a02.1 years (late mature age), and group C comprised men aged 58\u00a0\u00b1\u00a01.6 years (elderly). An integral method of quantitative assessment of power loads was used to determine 1 repetitions maximum (RM) and load parameters for each anaerobic energy supply mode. Resistance levels were evaluated based on adaptive-compensatory responses to training stimuli, using heart rate variability (HRV) and biochemical blood markers (creatine phosphokinase (CPK), lactate dehydrogenase (LDH), testosterone, cortisol).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Pre-exercise results showed that participants in groups A and C exhibited more tense heart rhythm regulation, with autonomic balance shifted toward sympathetic dominance. Group B showed creatine phosphokinase activity in the blood that was twice as high as in the other groups. Cortisol levels in group C were on average 17.6% higher than in groups A and B. Post-exercise results under the creatine phosphokinase energy supply mode revealed increased autonomic regulation and decreased sympathetic tone in groups B and C. In contrast, Group A showed heightened heart rate regulation tension (standard deviation of RR intervals (SDNN) \u221238.5%) and increased central sinus rhythm regulation (very low frequency (VLF) +34.3%). In groups B and C, creatine phosphate was the primary energy source, while in group A, due to insufficient creatine phosphate reserves, muscle glycogen was additionally utilized, leading to increased blood LDH (+94.7%) and cortisol (+133.2%). Under the anaerobic glycolysis mode, groups A and B showed increased vagal influence on the sinus node, while group C exhibited increased sympathetic tone (low frequency (LF) +11.4%) and reduced autonomic regulation (high frequency (HF) \u22125.9%). In group A, only LDH activity increased (+90.2%) compared to rest. Cortisol levels decreased significantly in groups A (\u221221.0%) and C (\u221212.4%), indicating activation of compensatory mechanisms.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>The findings underscore the need to develop tailored load adjustment strategies for mature and elderly individuals beginning bodybuilding. Load regimes should consider individual strength capacities and adaptive reserves. The use of heart rate variability (HRV) and blood biochemical markers is validated as an informative approach for assessing resistance to training-induced stress.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.7717\/peerj.19844","type":"journal-article","created":{"date-parts":[[2025,8,28]],"date-time":"2025-08-28T08:23:15Z","timestamp":1756369395000},"page":"e19844","source":"Crossref","is-referenced-by-count":4,"title":["Resistance of mature and elderly bodybuilders to anaerobic energy supply load"],"prefix":"10.7717","volume":"13","author":[{"given":"Andrii","family":"Chernozub","sequence":"first","affiliation":[{"name":"Lesya Ukrainka Volyn National University, Lutsk, Ukraine"},{"name":"The Scientific Research Center of Modern Kinesiology, Ujhorod, Ukraine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alla","family":"Aloshyna","sequence":"additional","affiliation":[{"name":"Lesya Ukrainka Volyn National University, Lutsk, Ukraine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Georgiy","family":"Korobeynikov","sequence":"additional","affiliation":[{"name":"National University of Ukraine on Physical Education and Sport, Kyiv, Ukraine"},{"name":"Institute of Psychology, German Sport University Cologne, Cologne, Germany"},{"name":"Uzbek State University of Physical Education and Sports, Chirchiq, Tashkent, Uzbekistan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vadym","family":"Koval","sequence":"additional","affiliation":[{"name":"Academician Stepan Demianchuk International University of Economics and Humanities, Rivne, Ukraine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yurii","family":"Havrylov","sequence":"additional","affiliation":[{"name":"Lesya Ukrainka Volyn National University, Lutsk, Ukraine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Liudmyla","family":"Sherstiuk","sequence":"additional","affiliation":[{"name":"Petro Mohyla Black Sea National University, Mykolaiv, Ukraine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vladimir","family":"Potop","sequence":"additional","affiliation":[{"name":"Institute of Phisical Education and Sport, Moldova State University, Chisinau, Moldova"},{"name":"Department of Physical Education and Sports, National University of Science and Technology Politehnica Bucharest, University Center Pitesti, Pitesti, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Consuela Andreea","family":"Timnea-Florescu","sequence":"additional","affiliation":[{"name":"Chiajna Medical Center, Chiajna, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Olivia Carmen","family":"Timnea","sequence":"additional","affiliation":[{"name":"Romanian-American University, Bucharest, 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