Purpose: This study aimed to investigate the time course of β-endorphin (β-EDP) levels in healthy males following an acute exercise, while considering their age and physical fitness (PF) level. Methods: Participants (N = 29, 20–65 years) were categorized in good PF young adult (YA1), excellent PF young adult (YA2), and excellent PF middle-aged adult (MA) group, depending on peak oxygen uptake and age. They underwent a maximal incremental cycling test, with blood samples collected at baseline (T0), 15 min (T1), and 24 h post-exercise (T2). Serum β-EDP levels were measured using an ELISA kit. Results: Significant increases in β-EDP levels were observed from T0 to T1 in all enrolled subjects. In YA1, levels rose from 170.1 to 202.5 pg/ml (p < 0.001), in YA2 from 188.4 to 230.3 pg/ml (p < 0.05), and in MA level increased from 153 to 189.3 pg/ml (p < 0.01). YA2 showed higher levels of β-EDP than MA in any time point (p < 0.05). All groups displayed a significant decrease of β-EDP from T1 to T2. Comparison between groups revealed that age significantly influenced baseline β-EDP levels, with notable differences between young and middle-aged individuals. Noteworthy, MA with excellent PF presented similar β-EDP levels to young with good PF. Conclusion: Acute exercise triggers a notable but transient elevation of serum β-EDP levels in both young and middle-aged adults, with the latter exhibiting lower baseline levels. Additionally, our findings suggest that age may have a greater influence on β-EDP secretion, both at rest and after physical exercise compared to PF level.

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.

This 12-week intervention study investigated the effects of a combined resistance and aerobic training (CT) program on body composition and functional capacity in sedentary middle-aged adults (n = 64; 32 males, 32 females; mean age 51.3 ± 6.2 years). Participants underwent supervised CT sessions three times weekly. Outcomes were assessed at baseline, week 6, and week 12, including fat mass (FM), fat-free mass (FFM), phase angle (PhA), handgrip strength (HGS), and estimated ̇VO2max. Significant reductions in FM (−3.6 ± 1.1 kg) and increases in FFM (+1.8 ± 0.7 kg) and PhA (+0.6 ± 0.2°) were observed. Functional capacity improved markedly, with HGS increasing by 4.2 ± 1.3 kg (males) and 3.1 ± 1.1 kg (females), and ̇VO2max by 4.6 ± 1.5 ml/kg/min. Correlational and regression analyses revealed PhA as a strong predictor of functional gains. No significant changes in diet or physical activity outside the intervention were noted. The findings support the utility of CT in enhancing health-related outcomes during middle age and suggest that PhA may serve as a practical biomarker of exercise responsiveness.

Background: Adiponectin is an adipokine with insulin-sensitizing, anti-inflammatory, and cytoprotective properties that also plays a key role in metabolic adaptation to exercise. Although its regulation after resistance exercise has been extensively documented, less is known about its short-term modulation and its correlation with muscle damage markers following resistance training. Methods: Nine resistance-trained young men completed two sessions of total-body resistance exercise: (1) high time under tension (TUT) (5-1-2-1 cadence, to failure; ETS1) and (2) moderate TUT (2-1-2-1 cadence, two repetitions in reserve; ETS2). Plasma and saliva samples were collected before exercise and at 15 min, 24 h, and 48 h after exercise to assess total adiponectin by ELISA. Plasma creatine kinase (CK) and a Visual Analog Scale (VAS) were also measured for muscle soreness. Results: Plasma adiponectin significantly decreased from baseline to 48 h post-exercise in both sessions (p < 0.001), with no differences between the TUT conditions. Salivary adiponectin remained unchanged. Although a significant increase in CK and a decrease in adiponectin were observed at the group level, correlation analysis revealed no significant linear relationship between the magnitude of CK elevation and adiponectin reduction. Conclusions: Overall, these findings support the role of adiponectin as a marker of acute metabolic adaptation to resistance exercise. Acute resistance exercise elicited a time-dependent decrease in circulating adiponectin, irrespective of TUT. The temporal pattern of adiponectin decrease coincided with the rise in muscle damage markers, yet the lack of direct correlation suggests distinct regulatory mechanisms, while the lack of salivary changes underscores the complexity of adipokine regulation in vivo and suggests that saliva is not a reliable indicator of changes in circulating adiponectin.