Effects of inspiratory muscle training combined with circadian rhythm-based running programs in children male football players

Abstract Background Research on the effect of inspiratory muscle training (IMT) on exercise performance is inconsistent. There are limited studies on the effect of IMT on fit child athletes who are more likely to develop inspiratory muscle fatigue and therefore benefit from IMT. However, the effects of IMT added to circadian rhythm-based running exercise interventions on physical fitness in fit child athletes have not been investigated. This study aimed to investigate the effects of inspiratory muscle training supplemented with six-week circadian rhythm-based running interventions on lower extremity strength, agility, and respiratory parameters in preadolescent male soccer players. Materials and Methods In the study, the participants were divided into 3 groups according to their answers to the Morningness-Eveningness Scale for Children. Participants who scored below 21 points were assigned as evening jogging + IMT (ERG + IMT), those who scored between 22–34 points were assigned as running only group (RG), and those who scored 35 points and above were assigned as morning jogging + IMT (MRG + IMT). Participants visited the laboratory three times at one-day intervals, before and after their 6-week running training program. Assessments included maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio. In addition, a 6-minute walk test (6MWT) and an agility performance test were performed. Results At the conclusion of the study, a significantly greater improvement in agility scores was observed in the MRG + IMT group compared to the ERG + IMT and RG groups (p < 0.001). Similarly, the 6MWT results revealed a higher performance improvement in the MRG + IMT group compared to the other groups (p < 0.001). In pulmonary function evaluations, significant increases in forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁) scores were similar between MRI + IMT and ERG + IMT groups, whereas these increases were more limited in the RG group. The FEV₁/FVC ratio increased statistically significantly more in the MRI + IMT group compared to the other groups (p = 0.003). Although there was no significant difference between the groups in maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) scores, all groups recorded similar rates of improvement (p > 0.05). Conclusion Running training was particularly effective in motor performance tests and some respiratory functions, and this effect became more pronounced when combined with a gradual loading IMT protocol. This supports the potential contribution of graded-load IMT in conditioning training programs for preadolescent children and the suitability of the MRG model. Trial registration Effects of Inspiratory Muscle Training Combined with Circadian Rhythmbased Running Programs in Children Football Players, ClinicalTrials.gov NCT06817486, Date 27012025.