**Background:** Aging is associated with osteopenia, sarcopenia, overweight, and dynapenia, increasing the risk of functional dependence and reduced quality of life. Resistance training (RT) and nutritional supplementation have shown promise as non-pharmacological strategies. Microfiltered seawater (SW) has demonstrated ergogenic effects in endurance sports, but its chronic effects combined with RT in older populations were unknown. This study aimed to evaluate the effects of 32 weeks of elastic band RT with or without SW supplementation on strength, bone health, body composition, and quality of life in postmenopausal women.
**Methods:** This was a 32-week prospective, randomized, double-blinded, placebo-controlled trial. Ninety-three untrained older women (age: 70.00 ± 6.26 years; BMI: 22.05 ± 3.20 kg/m²; body fat: 37.77 ± 6.38%) were allocated into four groups: RT+SW (n=35), RT+PLA (n=35), CON+SW (n=11), and CON+PLA (n=12). The RT intervention consisted of two weekly sessions (55-60 min) of whole-body exercises with elastic bands at submaximal intensities (85% of 1RM for high intensity, 65-70% for moderate intensity). Participants consumed 20 mL of microfiltered SW or placebo (water) just before each session. Outcomes included isokinetic strength (hip adduction, knee flexion, elbow flexion at 60 and 180°/s) measured by Biodex dynamometer; bone mineral density (global, hip, spine) by DXA; bone turnover markers (P1NP and BCTX/1000) by automated Roche ECLIA system; body composition by DXA; and quality of life by SF-36 questionnaire. Statistical analyses used two-way mixed ANOVA with Bonferroni post hoc corrections.
**Key Results:** Seventy-seven participants completed the 32-week intervention (17.2% dropout rate; ~75% attendance). Both RT groups significantly improved all isokinetic strength variables (p < 0.05), with greater effect sizes in the RT+SW group, though between-group differences were non-significant. Both RT groups showed significant improvements in hip BMD, P1NP (bone formation marker), and BCTX/1000 (bone resorption marker). The RT+SW group additionally showed significant improvements in global BMD and spine BMD, while RT+PLA did not. For body composition, RT+SW significantly improved all variables; RT+PLA improved muscle mass and body fat percentage but not fat mass (kg). Both control groups showed non-significant variations. For quality of life, both RT groups improved almost all SF-36 dimensions, with significantly greater improvements in bodily pain for RT+SW compared to controls. Significant between-group differences (RT groups vs. controls) were found in isokinetic strength, body fat percentage, and bodily pain. Non-significant differences existed between RT+SW and RT+PLA for all outcomes.
**Clinical Implications:** This study demonstrates that a 32-week elastic band resistance training program is effective for improving strength, bone health markers, body composition, and quality of life in postmenopausal women. While microfiltered seawater supplementation showed larger effect sizes across most outcomes, the differences were not statistically significant compared to RT alone, suggesting that RT is the primary determinant of adaptations. Elastic band training represents a safe, portable, and accessible exercise modality for older adults. The significant improvements in bone formation markers (P1NP) and reductions in bone resorption markers (BCTX/1000) in both RT groups support the role of resistance exercise in bone health management. The study was limited by the absence of acute effect measurements and the relatively low mineral concentrations in the SW supplement compared to other studies.