Layout 1 Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 Physical Exercise (PE) induces a range of physiological adaptations that enhance both endurance and strength, contributing not only to improved physical performance but also to long-term health benefits.1 Endurance training optimises cardiovascular efficiency, increases maximal oxygen uptake, and drives mitochondrial biogenesis,2 thereby enhancing endurance performance and capacity.3 Strength training, on the other hand, promotes muscle hypertrophy, neural adaptations, and increases in maximal force production, collectively augmenting physical power and functional capacity.4 Together, these adaptations improve quality of life and reduce the risk of age-related diseases.5-7 More and more articles about the effectiveness of exercise on performance and health are focusing on the study of molecular responses to exercise, with significant efforts directed at better studying and characterising the activity of exercise-induced signalling molecules termed “exerkines”.8 Exerkines encompass molecules of various biological origins and are released in response to both acute and chronic exercise, mediating their effects through endocrine, paracrine, and autocrine pathways to facilitate inter-organ communication. Exerkines are produced by multiple systems -including musculoskeletal, cardiovascular, nervous, and immune systems- and contribute to the complex, systemic effects of exercise.9 This emerging field offers promising avenues for understanding the complex molecular landscape shaped by exercise. Among exerkines, irisin, discovered by Boström in 2012,10 is released in response to PE, both in mice and humans. Indeed, physical activity activates the Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α) pathway, leading to increased expression of Fibronectin type III domain-containing protein 5 (FNDC5). The FNDC5 protein undergoes proteolytic cleavage in its extra cytoplasmatic part, resulting in the formation of irisin, which is subsequently released into the bloodstream. The first identified function of irisin was promoting the «browning» of White Adipose Tissue (WAT) into Brown Abstract Irisin’s response to Resistance Exercise (RE) remains unclear. We investigated plasma and salivary irisin levels following acute moderate load/high volume (ML/HV) RE and explored correlations with muscle damage markers. Eight healthy, resistance-trained young males (23.3±2.5 yrs) completed one ML/HV RE session (full-body, 30 sets to failure, 70% 1RM). Plasma/saliva irisin, plasma Creatine Kinase (CK), and Visual Analogue Scale (VAS) for muscle soreness were assessed at baseline, 15 min, 24h, and 48h post-exercise. Plasma irisin increased significantly by ~9% (p=0.01) and salivary irisin by ~4% (p=0.02) at 15 min post-exercise, returning towards baseline by 24h. A strong correlation (rho=0.8, p=0.03) existed between percentage changes in plasma and salivary irisin at 15 min. CK and VAS peaked at 24h (p<0.001; p=0.02 vs 48h, respectively), but showed no significant correlation with irisin changes. Acute ML/HV RE elicits a transient increase in plasma and salivary irisin. Saliva may be a useful non-invasive proxy for irisin changes post-RE. This acute irisin response appears independent of EIMD markers in this population. Findings require confirmation in larger studies. Key Words: irisin; resistance exercise; saliva; acute exercise; creatine kinase; exercise-induced muscle damage; myokine. Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Luigi Marano,1,2 Sara Missaglia,1,2 Eleonora Martegani,1,2 Andrea Bonanomi,3 Chiara Tremolada,4 Daniela Tavian,1,2 Ferdinando Cereda5 1Laboratory of Cellular Biochemistry and Molecular Biology, CRIBENS, Catholic University of Sacred Heart, Milan, Italy; 2Department of Psychology, Catholic University of Sacred Heart, Milan, Italy; 3Department of Statistical Science, Catholic University of Sacred Heart, Milan, Italy; 4Bachelor’s degree in Exercise and Sport Sciences, Catholic University of Sacred Heart, Milan, Italy; 5Department of Education, Catholic University of Sacred Heart, Milan, Italy. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License (CC BY-NC 4.0) which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. - 302 - Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 Adipose Tissue (BAT).10 However, with the growing body of evidence regarding its effects, additional functions of irisin have been identified. In addition to its role in adipose tissue, recent research has shown that irisin also affects various physiological processes across multiple organs, including enhancing muscle metabolism, supporting bone health, protecting cardiovascular function, improving liver metabolism, and offering neuroprotective effects.11 A significant number of articles have already been published on the acute irisin response to exercise. However, the existing body of evidence is highly heterogeneous, particularly in terms of sampling timing (ranging from immediately after exercise to 24 hours post-exercise,12-14 biological sample employed for analysis (saliva,15 plasma,16 serum,14 muscle biopsy17), participant health and fitness status18 and last training type and training variables used.19 While the evidence regarding Aerobic Exercise (AE) and irisin production is relatively clear, the results from Resistance Exercise (RE) are less consistent. This research gap is due to both a smaller number of studies on the acute irisin response to RE compared to AE, and the fact that conclusions from the available studies are not unidirectional. In fact, while three studies report a clear increase in circulating irisin levels,20,21,22 others suggests no changes.17,23 Therefore, further investigation is needed to explore the irisin response to RE with different variables in healthy population. To address this gap, we aimed to evaluate whether moderate load/high volume RE could lead to increased plasma and salivary levels of irisin, by also considering exercise-induced muscle damages (EIMD). Materials and Methods Participants Eight young healthy male participants (age, 23.3±2.5 years; BMI, 24.5±2.4 kg/m2; RT (resistance training) experience 4.9±2.5 years) were recruited. To take part in this study, subjects must have to meet the following inclusion criteria: aged less than 39 years, more than 18, have a body mass index (BMI): ≤ 25 kg/m2, be at least moderately active, have an experience with RT of at least six months of regular practice (minimum 2 sessions per week). Only male partic- ipants were recruited to minimise potential variability as- sociated with hormonal fluctuations inherent in the female menstrual cycle, which could influence metabolic and irisin responses. Experienced individuals were chosen to ensure proficiency in resistance exercise techniques, thereby re- ducing the risk of injury and variability in physiological re- sponses due to learning effects. Exclusion criteria for the study, included history of neurological disorders, muscu- loskeletal impairments, motor restrictions, pharmacother- apy, recent myocardial infarction, severe cardiac arrhythmia, unstable angina, hypertension, and metabolic disease. None of them were current smokers. Procedures The experimental protocol used in this study is presented in Figure 1. For each participant a period composed of 2 weeks was used to ensure them enough balance between training and recovery within sessions. First week experimental proce- - 303 - Figure 1. Graphical representation of the procedures. Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 dures consisted of three sessions used with the twofold pur- pose of familiarisation and load determination. These three sessions were organised as follows: ten repetition maxi- mum test session (10-RM), a Time Under Tension famil- iarization session (TUT) and one repetition maximum test session (1-RM). Between each testing session participants stayed at rest for at least 24h. Thereafter in week 2 the Moderate Load/High Volume (ML/HV) Experimental Testing Session (ETS) was performed. Each session was conducted in a private gym with a controlled environment with a humidity level below 60% and a temperature range of 18°C to 22°C. During this period, participants were in- structed to abstain from any form of exercise, that range from moderate to vigorous activity, from at least 48 hours before the experimental session. Before each session, both test and experimental, we advise the participants to have a consistent sleep routine, not consume alcoholic beverages and caffeinated product or other stimulants. All assess- ments were conducted between 09:00 a.m. and 1:00 p.m. to minimize potential bias from circadian rhythms. During familiarisation sessions anthropometric parameters were analysed, including Body Mass (BM) and height measure- ments, and BMI calculation. BM and height were meas- ured using a mechanical scale (Seca 762, Hamburg, Germany) and a stadiometer (Seca 217, Hamburg, Ger- many), respectively, following procedures previously de- scribed.24 The analysis of body composition and hydration status was assessed using Bioelectrical Impedance Analy- sis (BIA) (BIA 101 BIVA® PRO IPS, ItaAkern s.r.l, Pisa - Italy). For study the molecular response to exercise, this study underwent the sampling of venous blood and saliva at 4 time points, for experimental testing session: pre-ex- ercise (baseline), 15-minute (15 min), 24 hours (24 hrs.) and 48 hours (48 hrs.) post exercise. At 24 hrs. and 48 hrs., VAS scale (0-10 arbitrary units, A/U, derived from a 100mm line) was administered to assess the individual per- ception of muscle soreness after exercise. Exercise test and exercise program Test session (10-RM and 1-RM) were conducted following the procedures suggested by the American College of Sports Medicine (ACSM).24 Between these two load-deter- mination sessions (10-RM and 1-RM), we conducted a sep- arate, lower-intensity, lower-volume session specifically to familiarize participants with the prescribed 5-1-2-1 time under tension (TUT) cadence to be used during the experi- mental testing session, ensuring proper execution speed and minimizing potential effects from coordination factors dur- ing the ETS. We opted for isotonic gym machines to mini- mize potential effects from coordination factors. The protocol provided one exercise for each larger muscle groups and were administered with this sequence for all ses- sions, both test and experimental: 90° Leg Press (LP), Prone Lat Machine Pulldown, Prone Lying Leg Curl, Seated Chest Press, Leg Extension, Seated Shoulder Press, Standing Cable Triceps Extension, Stand- ing Biceps Dumbbells Curl. These exercises were selected to recreate a total body split routine largely used between gym members. The total number of sets during ETS was 30, with 4 sets for lower and upper body exercises (i.e. the larger muscles) and 3 sets for arms exercises (biceps and triceps). For ETS the load used correspond to the 70% of the individ- ual 1-RM, tested during familiarization session. This load was used for the purpose to induce either a good MechT (mechanical tension, the force experienced by muscle fi- bres), and as it is in the continuum spectrum of rec- ommended load for inducing adaptation to resistance exercise such as muscle strength, hypertrophy and local en- durance.25 To have also a high MetS (metabolic stress, the accumulation of metabolites) the 30 sets, were carried out to muscular failure as well with a TUT of 5-1-2-1, empha- sising the eccentric phase of the movements. Rest intervals between sets were standardized at 90 seconds for all exercises to maintain consistent exercise density (i.e., work-to-rest ratio) and metabolic stress. The exercise session consisted of a total of 220 repetitions, with a standard deviation of 31.49. The corresponding vol- ume load, calculated as weight × repetitions × sets, was 121704.8±29592.33. A trained researcher supervised each workout session care- fully so that exercise prescriptions were correctly admin- istered during resistance exercise session (RES, e.g., number of repetitions, rest and movement’ speed). Compli- ance with the study was 100% of the programmed sessions. Biological sample treatment and biochemical analyses Blood samples were collected using a vacutainer system and immediately centrifuged at 11,000 rpm for 10 minutes. The plasma was then separated and stored at -80°C until analysis. For saliva samples, participants rinsed their mouths thoroughly five times without swallowing before filling a 1.5 ml Eppendorf tube with saliva. Saliva samples were centrifuged for 4 minutes and stored at -80°C until analysis. The levels of plasmatic and salivary irisin were detected by an Enzyme-Linked Immunosorbent Assay kit (ELISA) (Irisin kit: Cat. EK-067-29 Phoenix Pharmaceuti- cals) using the Victor Nivo multimode plate reader (Perki- nElmer), following the manufacturer’s instructions. All samples were analysed in duplicate. The intra- and inter- assay Coefficients of Variation (CVs) for plasma and sali- vary irisin, as determined in our laboratory following manufacturer’s instructions, were <10% and <15%, respec- tively. All samples conformed to the parameters of the stan- dard curve provided by manufacturer instruction. Creatine Kinase (CK) levels were measured using a Chemilumines- cent Immunoassay method (CLIA, Siemens Healthcare Diagnostics, USA). Statistical analyses JASP (Version 0.19.1, JASP Team 2024, Netherlands) was used to analyse the data. Results were considered significant when p<0.05. Data distribution was assessed using Shapiro- Wilk test. Given the very limited sample size (N=8), even if data were normally distributed, we opted to use nonpara- metric tests to enhance analytical robustness. Differences in irisin and CK across all the time points, were assessed using Friedman test. Spearman correlation analysis was conducted to test the correlations between percentage - 304 - Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 changes in plasma and salivary irisin across time points, considering correlation strength as follows: 0.00–0.10 neg- ligible; 0.10–0.39 weak; 0.40–0.69 moderate; 0.70–0.89 strong; and 0.90–1.00 very strong correlation. Results Participants descriptive characteristics In Table 1, the descriptive characteristics of participants are reported. According to ACSM’s 2021 ratio between BM in kg and the 1RM of LP percentile (BM/1RM LP) participants could be defined as well trained, as their percentile classifies them as “above average” for individuals of their age. Indeed, as also shown in the table, participants had a great experience in RT practice. Plasma and salivary irisin values This study primarily aimed to evaluate whether ML/HV RES induce an increase in plasma and salivary irisin levels. A significant rise in plasma irisin concentration was ob- served between baseline and 15 min (Figure 2a). Specifi- cally, plasma irisin levels increased from 10.3±1.04 to 11.1±1.5 ng/ml, (mean increase + 9%; p = 0.01). Following this acute elevation, irisin levels decreased to 10.6±1.06 ng/ml (p = 0.05) (24 h) and then to 10.5±1.03 ng/ml (48 h). A significant increase in salivary irisin levels has been found too. Interestingly salivary irisin increased from 0.053±0.007 ng/ml to 0.055±0.008 ng/ml (mean increase: + 4%; p = 0.02) from baseline to 15 min post-exercise (Figure 2b). Correlation between plasma and salivary percentage irisin changes The secondary aim of this study was to determine whether salivary and plasma irisin exhibit similar responses to the same exercise stimulus. To address this, a correlation anal- ysis was conducted on the percentage changes in salivary and plasma irisin from baseline to 15 minutes after exercise. A significant correlation was observed between baseline and 15 min, where plasma and salivary irisin demonstrated a similar trend. Spearman’s rank correlation coefficient con- firmed a significant correlation (ρ = 0.8; p = 0.03). These findings are reported in Figure 2c. Plasma creatine kinase levels and visual analogue scale value Finally, this study aimed to assess the amount of EIMD and delayed onset muscle soreness (DOMS), as evaluated through plasma CK levels (Figure 3a) and Visual Ana- logue Scale (VAS) scores (Figure 3b), respectively. As ex- pected CK levels exhibited significant changes. CK concentrations increased from 128.5±26.31 U/L to 279.8±112.71 U/L, reaching a peak 24 hour post-exercise, - 305 - Table 1. Participants descriptive characteristics. Variables Mean Standard deviation n 8 / Age (yrs) 23.3 2.5 Height (cm) 176.2 8.5 Body mass (kg) 76.1 8.6 BMI kg/m2 24.5 2.4 Muscle mass (kg) 45.4 4.6 % Muscle mass 59.8 3.5 % FM 17.1 4.3 % FFM 83.0 4.3 Fat mass (kg) 13.1 4.3 Resistance training experience (yrs) 4.9 2.5 Ratio BM/1RM LP 2.8 0.33 ACSM’s ratio BM/1RM LP percentile 90.0 0.0 Descriptive values are reported as mean and standard deviation. BM, body mass; BMI, body mass index; FFM, fat free mass; FM, fat mass; 1RM, one repetition maximum; LP, leg press. Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 382.0±164.18 U/L, before declining to 246.3±86.56 U/L at 48 hours. The Friedman test revealed significant differ- ences across the following time points: baseline to 15 min - 24 hours and 48 hours post-exercise (p < 0.001); 15 min to 24 hours (p = 0.01); and 24 hours to 48 hours post-ex- ercise (p = 0.03). Consistent with the CK data, VAS scores showed signifi- cant differences in response to exercise, highlighting the impact of EIMD on post-exercise pain perception. Wilcoxon signed-rank test indicated a significant reduction in VAS scores from 24 hours (5.7±2.52 A/U) to 48 hours post-exercise (3.4±2.52 A/U, p = 0.02). Furthermore, no significant correlation was found between the percentage change in plasma or salivary irisin at 15 mi- nutes post-exercise and the peak changes in CK or VAS scores (data not shown, p > 0.05 for all correlations). - 306 - Figure 2. Differences in plasma (a) and salivary (b) iri- sin levels in response to ETS and Correlation between percentage changes in plasma and salivary irisin levels between baseline and 15 min (c). Figure 3. Differences in plasma Creatine Kinase con- centration (3a) and Visual Analogue Scale values (3b) in response to ETS. Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 Discussion This investigation sought to elucidate the acute plasma and salivary irisin response to a demanding Moderate Load/High Volume (ML/HV) resistance exercise (RE) pro- tocol in resistance-trained young men, and to explore po- tential associations with markers of Exercise-Induced Muscle Damage (EIMD). Our principal finding is a signif- icant, albeit transient, increase in both plasma (~9%) and salivary (~4%) irisin concentrations 15 minutes post-exer- cise. This acute elevation suggests that this specific type of RE, characterised by substantial Mechanical Tension (MechT) and Metabolic Stress (MetS) induced by exercise to failure across multiple sets with controlled tempo, serves as an effective stimulus for irisin release. While direct com- parisons with endurance exercise are complex due to vary- ing protocols and irisin responses reported in the literature, this acute response is noteworthy within the context of RT- induced irisin changes. The observed immediate post-exercise rise in irisin aligns with some previous RE studies reporting increases shortly after exercise cessation,20,21,22 yet contrasts with others, no- tably He et al. (2018)23 and Pekkala et al. (2013),17 who found no significant change at 15 minutes post-exercise fol- lowing a lower-volume, isolated knee extension protocol. This discrepancy likely underscores the importance of the exercise stimulus characteristics. Our ML/HV protocol in- volved a substantially greater total work volume, engaged significantly more muscle mass via a full-body routine, and purposefully induced high metabolic stress through sets to failure with controlled eccentric emphasis (5-1-2-1 tempo). These factors may have contributed to the observed irisin surge, possibly by triggering cleavage of pre-existing FNDC5 protein located on the muscle cell membrane. This rapid, post-translational mechanism could explain the quick appearance of irisin in circulation shortly after exercise. The return towards baseline levels by 24 hours suggests this iri- sin surge is a feature of the immediate post-exercise recov- ery phase, rather than a sustained response. A key secondary finding is the strong positive correlation (rho=0.8) between the percentage changes in plasma and salivary irisin at the 15-minute post-exercise time point. This indicates that, at least for assessing acute, exercise-in- duced fluctuations, saliva may serve as a valuable, non-in- vasive proxy for plasma irisin. While baseline and absolute concentrations differ between the fluids, the concordance in their relative response to the RE stimulus is noteworthy. This finding warrants further investigation, as salivary sam- pling offers considerable logistical advantages for future studies examining acute exercise responses, although cau- tion is needed as saliva may reflect punctual changes rather than an integrated systemic level over time.15 We also investigated the response of EIMD markers, namely plasma Creatine Kinase (CK) and perceived mus- cle soreness (VAS). As anticipated, both CK and VAS demonstrated significant increases, peaking 24 hours post- exercise, confirming the efficacy of the ML/HV protocol in inducing muscle damage and delayed onset muscle soreness26. While direct molecular mechanisms were not assessed in this study, the findings prompt consideration of the cellu- lar events triggered by ML/HV RE. In particular it is rea- sonable to speculate that the acute irisin release is prima- rily driven by rapid post-translational modifications, specifically the cleavage of membrane-bound FNDC5, rather than new protein synthesis. Furthermore, the sys- temic hormonal milieu (e.g., acute changes in catechola- mines, growth hormone, or testosterone) induced by such demanding exercise could potentially modulate FNDC5 expression or irisin processing, representing an area for future research integrating hormonal and myokine meas- urements. Several limitations must be acknowledged. The small sample size restricts statistical power and the generalis- ability of our findings. The study population consisted solely of young, healthy, resistance-trained men, preclud- ing extrapolation to females, older adults, untrained in- dividuals, or clinical populations. Additionally, the trained status of our participants might have attenuated the EIMD response and potentially influenced the magnitude of irisin release compared to untrained individuals, a factor that warrants consideration in future studies. The focus on a single, specific ML/HV RE protocol means results may not apply to other RE modalities differing in intensity, vol- ume, or contraction type. Conclusions In conclusion, this study provides preliminary evidence that an acute bout of high-volume, moderate-load resistance ex- ercise performed to failure elicits a significant, transient in- crease in both plasma and salivary irisin concentrations 15 minutes post-exercise in trained young men. Saliva shows promise as a non-invasive proxy for assessing these acute changes. Importantly, this early irisin response appears tem- porally and mechanistically distinct from the subsequent development of EIMD markers like CK and VAS. These findings highlight the sensitivity of irisin to specific RE sti- muli characterised by high metabolic stress and volume, but suggest its acute release is not directly coupled to the mag- nitude of delayed muscle damage in this context. Further research employing larger sample sizes, diverse popula- tions, and potentially muscle biopsies is required to confirm these observations and fully elucidate the molecular mech- anisms governing irisin regulation in response to different resistance exercise paradigms. List of abbreviations 1-RM, One Repetition Maximum 10-RM, Ten Repetition Maximum A/U, Arbitrary Units ACSM, American College of Sports Medicine AE, Aerobic exercise BAT, Brown Adipose Tissue BIA, Bioelectrical Impedance Analysis BM, Body Mass BMI, Body Mass Index CERPS, Ethics Commission of the Department of Psy- chology - 307 - Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 CK, Creatine Kinase CLIA, Chemiluminescent Immunoassay DOMS, Delayed Onset Muscle Soreness EIMD, Exercise-Induced Muscle Damage ELISA, Enzyme-Linked Immunosorbent Assay ETS, Experimental testing session FFM, Fat-Free Mass FM, Fat Mass FNDC5, Fibronectin Type III Domain-Containing Protein 5 LP, Leg Press MechT, Mechanical tension MetS, Metabolic stress ML/HV, moderate load/high volume PE, Physical exercise PGC1-α, Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-Alpha REP, Repetition RIR, Repetitions in Reserve RT, Resistance training RE, Resistance exercise RES, Resistance exercise session TUT, Time Under Tension VAS, Visual Analogue Scale VL, Volume Load WAT, White adipose tissue Acknowledgments The authors would like to thank the volunteers for their par- ticipation and cooperation during the study, Professor Paola Vago for her fundamental contribution during recruitment process, Professor Alvaro Mordente for his scientific sup- port and Dr. Giorgio Bazzano for his valuable technical as- sistance. Funding This study was supported by internal funding provided by Catholic University of Sacred Heart in Milan. Conflicts of interest The authors declare no conflicts of interest. Ethical approval The study was conducted in accordance with the Declara- tion of Helsinki and approved by the Institutional Ethics Committee of the department of Psychology at the Catholic University of the Sacred Heart of Milan (CERPS) (protocol code n: 36/24). Author contributions Conceptualization, DT and FC; methodology, LM and FC; writing—original draft preparation, LM; writing—review and editing, LM, DT, SM and FC; designed and supervised the research, FC and DT; administered exercise, LM, CT and FC; molecular investigation, SM, EM and DT; statisti- cal analysis, AB and LM; exercise protocol results interpre- tation, LM and FC. All authors have read and agreed to the published version of the manuscript. Informed consent statement All participants in this study signed a written informed con- sent form for participation and anonymized information publication. Data availability statement The data that support the findings of this study are available from the corresponding author upon reasonable request. Corresponding author Ferdinando Cereda, Catholic University of Sacred Heart, Department of Education, Largo Gemelli 1, 20123 Milan, Italy. Tel.: +390272342209. ORCID ID: 0000-0002-3120-0684 E-mail: ferdinando.cereda@unicatt.it. Co-authors Luigi Marano ORCID ID: 0000-0002-9833-8055 E-mail: luigi.marano@unicatt.it Sara Missaglia ORCID ID: 0000-0001-6551-6698 E-mail: sara.missaglia@unicatt.it Eleonora Martegani ORCID ID: 0000-0002-8103-686X E-mail: eleonora.martegani@unicatt.it Andrea Bonanomi ORCID ID: 0000-0003-2857-1430 E-mail: andrea.bonanomi@unicatt.it Chiara Tremolada ORCID ID: 0009-0004-9662-7541 E-mail: chiara.tremolada03@icatt.it Daniela Tavian ORCID ID: 0000-0003-3333-0068 E-mail: daniela.tavian@unicatt.it References 1. Hughes DC, Ellefsen S, Baar K. Adaptations to endur- ance and strength training. Cold Spring Harb Perspect Med 2018;8:a029769. 2. Hackney AC. Molecular and physiological adaptations to endurance training. In: Concurrent aerobic and strength training: Scientific basics and practical appli- cations. 2019: pp. 19-34. - 308 - mailto:ferdinando.cereda@unicatt.it mailto:luigi.marano@unicatt.it mailto:sara.missaglia@unicatt.it mailto:eleonora.martegani@unicatt.it mailto:andrea.bonanomi@unicatt.it mailto:chiara.tremolada03@icatt.it mailto:daniela.tavian@unicatt.it Plasma and salivary irisin response to moderate load/high volume resistance exercise in young, resistance-trained men Eur J Transl Myol 35 (3) 13957, 2025 doi: 10.4081/ejtm.2025.13957 3. Brooks GA. Bioenergetics of exercising humans. Compr Physiol 2012;2:537-62. 4. Folland JP, Williams AG. Morphological and neurolog- ical contributions to increased strength. Sports Med 2007;37:145-68. 5. Cartee GD, Hepple RT, Bamman MM, Zierath JR. Ex- ercise promotes healthy aging of skeletal muscle. Cell Metab 2016;23:1034-47. 6. McGregor RA, Cameron-Smith D, Poppitt SD. It is not just muscle mass: a review of muscle quality, composi- tion and metabolism during ageing as determinants of muscle function and mobility in later life. Longevity Healthspan 2014;3:1-8. 7. Zampieri S, Pietrangelo L, Loefler S, et al. Lifelong physical exercise delays age-associated skeletal muscle decline. J Gerontol Series A: Biomed Sci Med Sci 2015; 70:163-73. 8. Safdar A, Saleem A, Tarnopolsky MA. The potential of endurance exercise-derived exosomes to treat metabolic diseases. Nat Rev Endocrinol 2016;12:504-17. 9. Chow LS, Gerszten RE, Taylor JM, et al. Exerkines in health, resilience and disease. Nat Revi Endocrinol 2022;18:273-89. 10. Boström P, Wu J, Jedrychowski MP, et al. A PGC1-α- dependent myokine that drives brown-fat-like devel- opment of white fat and thermogenesis. Nature 2012; 481:463-8. 11. Liu S, Cui F, Ning K, et al. Role of irisin in physiology and pathology. Front Endocrinol 2022;13:962968. 12. Fox J, Rioux BV, Goulet EDB, et al. Effect of an acute exercise bout on immediate post-exercise irisin concen- tration in adults: A meta-analysis. Scand J Med Sci Sports 2018;28:16-28. 13. Kazeminasab F, Sadeghi E, Afshari-Safavi A. Compar- ative impact of various exercises on circulating irisin in healthy subjects: a systematic review and network meta- analysis. Oxidative Med Cell Longev 2022;2022: 8235809. 14. Tommasini E, Missaglia S, Vago P, et al. The time course of irisin release after an acute exercise: relevant implications for health and future experimental designs. Eur J Translat Myol 2024;34:12693. 15. Missaglia S, Tommasini E, Vago P, et al. Salivary and serum irisin in healthy adults before and after exercise. Eur J Translat Myol 2023;33:11093. 16. Huh JY, Panagiotou G, Mougios V, et al. FNDC5 and irisin in humans: I. Predictors of circulating concentra- tions in serum and plasma and II. mRNA expression and circulating concentrations in response to weight loss and exercise. Metabolism 2012;61:1725-38. 17. Pekkala S, Wiklund PK, Hulmi JJ, et al. Are skeletal muscle FNDC5 gene expression and irisin release reg- ulated by exercise and related to health? J Physiol 2013;591:5393-400. 18. Colpitts BH, Rioux BV, Eadie AL, et al. Irisin response to acute moderate intensity exercise and high intensity interval training in youth of different obesity statuses: A randomized crossover trial. Physiol Rep 2022;10: e15198. 19. Qiu S, Cai X, Sun Z, et al. Chronic exercise training and circulating irisin in adults: A meta-analysis. Sports Med 2015;45:1577-88. 20. Huh JY, Siopi A, Mougios V, et al. Irisin in response to exercise in humans with and without metabolic syn- drome. J Clin Endocrinol Metab 2015;100:E453-E7. 21. Nygaard H, Slettaløkken G, Vegge G, et al. Irisin in blood increases transiently after single sessions of in- tense endurance exercise and heavy strength training. PloS One 2015;10:e0121367. 22. Tsuchiya Y, Ando D, Takamatsu K, Goto K. Resistance exercise induces a greater irisin response than endur- ance exercise. Metabolism 2015;64:1042-50. 23. He Z, Tian Y, Valenzuela PL, et al. Myokine response to high-intensity interval vs. resistance exercise: an in- dividual approach. Front Physiol 2018;9:1735. 24. Gibson AL, Wagner DR, Heyward VH. Advanced fit- ness assessment and exercise prescription: Human ki- netics; 2024. 25. Schoenfeld B, Grgic J, Plotkin D, Van Every D. Load- ing recommendations for muscle strength, hypertrophy, and local endurance: a re-examination of the repetition continuum. Sports 2021;9:9020032. 26. Spada TC, Silva JM, Francisco LS, et al. High intensity resistance training causes muscle damage and increases biomarkers of acute kidney injury in healthy individ- uals. PloS One 2018;13:e0205791. Disclaimer All claims expressed in this article are solely those of the authors and do not necessarily represent those of their af- filiated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher. Submitted: 7 May 2025. Accepted: 26 May 2025. Early access: 9 July 2025. - 309 -