Effects of 4-Week Inspiratory Muscle Training on Sport Performance in College 800-Meter Track Runners

Background and objectives: Respiratory muscle fatigue is one of the important factors limiting sports performance due to the metaboreflex. This reflex will cause a decrease in blood flow to the extremities and accelerate exercising limb fatigue. Previous studies found that inspiratory muscle training (IMT) can effectively enhance the respiratory muscle endurance and reduce fatigue during long-duration exercise or aerobic exercise, thereby enhancing athletic performance. However, the mechanism between inspiratory muscle strength, change of limb blood flow and sports performance still requires investigation, especially in short-duration exercise, anaerobic or both aerobic and anaerobic exercise. The purpose of this study was to investigate the effects of 4-week inspiratory muscle training on respiratory muscle strength, limb blood flow change rate and sports performance in recreational 800-m college runners. Materials and Methods: Twenty healthy 800-m college runners randomized into the IMT group (11 subjects) and control group (9 subjects). IMT consisted of 30 inspiratory efforts twice daily, 5 days a week, with intensity at 50%, 60%, 70% and 80% of maximum inspiratory pressure (MIP) for 4 weeks, while a control group kept 50% of MIP for 4 weeks. An 800-m trial test, limb blood flow change rate by using Impedance Plethysmography, and MIP were as the outcome measured variables and be evaluated. All measured variables were assessed before and after 4-week IMT training. Two-way ANOVA was conducted for statistical analysis. Results: The results showed significantly interaction between groups and pre-posttest. IMT group significantly decreased limb blood flow change rate from 19.91 ± 11.65% to 9.63 ± 7.62% after received the IMT training program (p < 0.05). The MIP significantly improved from 112.95 ± 27.13 cmH2O to 131.09 ± 28.20 cm H2O in IMT group, and the 800-m trial test also shorted the running time from 162.97 ± 24.96 s to 156.75 ± 20.73 s. But the control group no significantly changed in MIP and 800-m trial test. Conclusions: Our results indicated that the 4-week IMT training (twice a day, 5 days a week) significantly improves participants’ inspiratory muscle strength, 800-m running performance and decreases the limb blood flow change rate.

E-Cigarette Use and Subclinical Cardiac Effects

ABSTRACTBACKGROUNDElectronic (e-) cigarettes are marketed as a safer alternative to conventional tobacco cigarettes. Although e-cigarettes contain a lower level of nicotine, the delivery method involves delivering an aerosolized bolus of poorly-characterized ultrafine particles that have unknown cardiovascular effects.METHODSWe studied apparently adult volunteers, free of any chronic disease, including: non-smoking controls, chronic e-cigarette users, and chronic tobacco cigarette smokers. After overnight abstinence, we used myocardial contrast echocardiography to measure acute increases in myocardial blood flow (MBF)induced by ischemic rhythmic handgrip stress, which causes sympathetically-mediated increases in myocardial work and oxygen demand and, in turn, shear stress, nitric oxide production, and coronary endothelial-dependent vasodilation.RESULTSIn non-smoking controls, handgrip stress increased myocardial blood flow, reflecting normal endothelial function. Chronic tobacco cigarette smokers demonstrated stress-induced blunting in myocardial blood flow change, when compared to non-smoking controls. Chronic e-cigarette smokers demonstrated a decrease, rather than increase, in myocardial blood flow change.CONCLUSIONChronic e-cigarette users demonstrated substantially impaired coronary microvascular endothelial function, even more pronounced than that seen in chronic tobacco cigarette users. These findings suggest that chronic e-cigarette use leads to measurable and persistent adverse vascular effects that are not directly related to nicotine.