Homer, Kai AHelms, Eric RSpence, Alyssa-Joy2025-01-292025-01-292025-01-17Physiol Rep, ISSN: 2051-817X (Print); 2051-817X (Online), Wiley, 13(2), e70156-. doi: 10.14814/phy2.701562051-817X2051-817Xhttp://hdl.handle.net/10292/18527Both resistance training (RT) and long-duration, high-intensity stretching induce muscular adaptations; however, it is unknown whether the modalities are complementary or redundant, particularly in well-trained individuals. A case-study was conducted on a competitive bodybuilder implementing long-duration, high-intensity stretching of the plantar flexors (60 min 6x/week for 12 weeks) in conjunction with their habitual RT. Ultrasound muscle architecture (muscle thickness [MT], fascicle length [FL], and pennation angle [PA]) measurements were collected at multiple sites at four weekly baseline sessions, six (mid) and 12 (post1) weeks following the commencement of the intervention, and a week after the intervention (post2) while isometric strength and range of motion (RoM) were obtained once at baseline, mid, post1, and post2. 2SD band plots were constructed to determine meaningful changes in MT, FL, and PA from the four baseline measures while percentage and absolute change across each timepoint were calculated for all variables. From baseline to post 1, RoM, strength, and MT increased 25.9%, 11.4%, and 7.4%-23.4%, respectively, while four MT and two PA sites exceeded the threshold for meaningful change. The combined stretching and RT protocols resulted in flexibility, strength, and MT adaptations; however, findings should be generalized with caution given the case-study nature of our investigation.© 2024 The Author(s). Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.http://creativecommons.org/licenses/by/4.0/case reportchronic stretchingmuscle architecturerange of motionresistance training0606 Physiology1103 Clinical Sciences1116 Medical Physiology3208 Medical physiologyHumansResistance TrainingMuscle Stretching ExercisesMaleMuscle, SkeletalAdultMuscle StrengthRange of Motion, ArticularWeight LiftingAdaptation, PhysiologicalMuscle, SkeletalHumansRange of Motion, ArticularAdaptation, PhysiologicalWeight LiftingAdultMaleMuscle StrengthMuscle Stretching ExercisesResistance TrainingJournal ArticleOpenAccess10.14814/phy2.70156