Efectos del entrenamiento de fuerza en la salud cardiovascular

Laburpena

Introduction: Cardiovascular health has drawn the attention of researchers and international organizations as it is one of the most reliable predictors of death and disability nowadays. Within endothelial function, blood pressure (BP) and arterial stiffness (AS) are two of the strongest cardiovascular risk predictors. Regular physical activity is considered as one of the major non-pharmacological cardiovascular disease's treatment and prevention strategies. Unlike other training modalities, the effects of resistance training on BP and AS have been less studied. Moreover, the results of previous research are inconclusive and sometimes contradictory. In this regard, there are still concerns about the safety of applying certain protocols, such as high-intensity or isometric resistance training, as they may be potentially dangerous for significantly increasing BP and AS. Aim: i) To gather evidence and analyze the acute and chronic effects of different modalities and manifestations of resistance training on cardiovascular health, expressed by BP and AS. ii) To generate statistical results that unify the contributions of scientific studies on the effects of resistance training on AS. iii) To acknowledge the acute effect of different intensities of lower-limb isometric resistance on BP. iv) To analyze the effects of high intensity resistance training with different degrees of effort on BP. Methodology: (I) The first study is a systematic review that evaluated the acute and chronic effects of resistance training on AS. Studies published in PubMed and SportDiscus databases between 1999 and April 2019 were reviewed. (II) Given the recent increase in the number of scientific papers, and the need and appropriateness of conducting a metaanalysis, a new systematic search of randomized controlled studies published up to October 2020 was conducted for the in the PubMed, SportDiscus, Medline and Web of Sciences databases. Nineteen studies, with a methodological quality of 12.58 ± 0.82 points (out of 15 possible) and a total of 626 participants were selected. (III) In the third study, the acute BP response to lower limb isometric resistance exercise, performed at different intensities (20, 40, 60 and 80% of IMF), from 25 healthy subjects (23.96 ± 2.95 years; 14 females) was analyzed. (IV) Finally, 24 subjects (25.25 ± 5.11 years; 12 females) participated in a single-group randomized experimental study examining the acute effects of two highintensity upper limb resistance training protocols, with different degrees of effort (20 and 40% velocity loss in the set), on BP. Results: (I) Regarding the chronic effects of resistance training, most groups showed large (d = -1.49 to -1.20) and moderate (d = -1.07) decreases, or small or trivial AS changes. In terms of acute effects, both large and very large (d = 3.88) AS decreases (d = -3.92) and increases (d = 1.24-1.48) were found. (II) No significant chronic effects of resistance training on AS were found (ES = -0.07; 95% CI: -0.59 to 0.45; p = 0.789). However, a single session produced significant acute increases (ES = 1.07; 95% CI: 1.55 to 0.59; p < 0.001). No other variable (age, gender, measurement method, upper vs. lower limbs, training intensity, duration or frequency) had a significant influence on AS for both acute and chronic interventions. (III) BP significantly increased as intensity increased. A very similar correlation was observed between BP values and absolute (R = 0.851, p = 0.00001; R = 0.842, p = 0.00001; R = 0.833, p = 0.00001) and relative intensity (R = 0.853, p = 0.00001; R = 0.839, p = 0.00001; R = 0.837, p = 0.00001). (IV) No significant pre-post BP differences were found for both the lower (20% speed loss; F = 0.185, p = 0.669) and the higher effort degree protocols (40% speed loss; F = -0.770, p = 0.454). Conclusions: With this Doctoral Thesis it can be concluded that resistance training is a cardiovascular-health safe modality, as it does not chronically increase AS, regardless of the intensity and type of exercise performed. Furthermore, hitherto controversial modalities, such as isometric or high-intensity resistance exercise training, also seem to be safe, as they do not increase short-term BP.