Ageing exacerbates the adverse effects of respiratory muscle fatigue on vascular function, locomotor muscle fatigue and exercise performance in males

Figures

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  FIGURE 1. Cardiovascular response to fatiguing ILT at 60% of maximal inspiratory pressure (ILT60%). MAP, HR, CO, TPR, limb blood flow (Q̇ L) and LVC response to ILT60% in young (YA, n = 10, group mean shown as blue squares, individual data as shaded blue lines) and master (MA, n = 10, group mean shown as red open squares, individual data as shaded red lines) athletes. Note that no change in the cardiovascular indices were observed after ILT2% and ILT2% ISO (data not shown for figure clarity). § P < 0.05 between YA and MA. CO, cardiac output; HR, heart rate; ILT, inspiratory loading task; LVC, limb vascular conductance; MAP, Mean arterial pressure; TPR, total peripheral resistance.

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  FIGURE 2. Time to exhaustion during the CWT. The constant workload cycling test was performed after the ILT at 60% of maximal inspiratory pressure (CWTILT60%) and, on separate days, after a sham condition (CWTILT2%). Group mean (bars), and individual (circles and lines) data are shown for each condition, with young athletes (YA, n = 10) represented by blue filled circles and master athletes (MA, n = 11) by red open circles. Power output was identical between CWTILT60% and CWTILT2%. * P < 0.05 between CWTILT60% and CWTILT2%; ** P < 0.001 between CWTILT60% and CWTILT2%; § P < 0.05 between YA and MA. CWT, constant workload cycling tests; ILT, inspiratory loading task.

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  FIGURE 3. Quadriceps muscle activation during the CWT. The RMS of the VL, VM and RF EMGs measured during exercise in young (YA, n = 10, black, left panel) and master (MA, n = 10, white, right panel) athletes was normalized to the M MAX recorded during the pre‐exercise MVC of the quadriceps (%MVC). CWT was performed following an ILT at 60% (CWTILT60%) and 2% (i.e., sham conditions CWTILT2% and CWTILT2%–ISO) of each participant's maximal inspiratory pressure. CWTILT60% and CWTILT2% were performed to exhaustion. CWTILT2%–ISO was interrupted at the time equal to that performed during CWTILT60%. CWT, constant workload cycling tests; ILT, inspiratory loading task; MVC, maximal voluntary isometric contraction; RF, rectus femoris; RMS, root mean square; VL, vastus lateralis; VM, vastus medialis.

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  FIGURE 4. Exercise‐induced neuromuscular fatigue. Pre‐ to post‐exercise difference in MVC, in potentiated twitch force evoked by a single electrical stimulation of the femoral nerve (QTSINGLE) and in VA in young (YA, n = 10, filled, left panel) and master (MA, n = 10, open, right panel) athletes. The CWT was performed following and ILT at 60% (CWTILT60%) and 2% (i.e., sham conditions CWTILT2% and CWTILT2%–ISO) of each participant's maximal inspiratory pressure. CWTILT60% and CWTILT2% were performed to exhaustion. CWTILT2%–ISO was interrupted at the time equal to that performed during CWTILT60%. * P < 0.05 between CWTILT2% and CWTILT2%–ISO; # P < 0.05 between CWTILT60% and CWTILT2%–ISO; † P < 0.05 between 15 s and the corresponding point; ‡ P < 0.05 between VA baseline and the corresponding point in CWTILT2%; § P < 0.05 between VA baseline and the corresponding point in CWTILT60%. CWT, constant workload cycling tests; ILT, inspiratory loading task; MVC, maximal voluntary contractions; VA, voluntary activation.

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  FIGURE 5. Metabolic and ventilatory response to the CWT. Changes in O2 uptake (V˙O2), CO2 production (V˙CO2), minute ventilation (V˙E), ventilatory equivalent for CO2 (V˙E/V˙CO2) and partial pressure of end tidal CO2 (PETCO2) during CWT in young (YA, n = 10, filled symbols, left panel) and master (MA, n = 11, open symbols, right panel) athletes. CWT was performed following and ILT at 60% (CWTILT60%) and 2% (i.e., sham conditions CWTILT2% and CWTILT2%–ISO) of each participant's maximal inspiratory pressure. CWTILT60% and CWTILT2% were performed to exhaustion. CWTILT2%–ISO was interrupted at the time equal to that performed during CWTILT60%. CWT, constant workload cycling tests; ILT, inspiratory loading task.

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  FIGURE 6. Ratings of perceived breathing and leg discomfort during the CWT. Perceptual responses to CWT, in young (YA, n = 10, filled, left panels) and master (MA, n = 11, open, right panel) athletes. CWT was performed following and ILT at 60% (CWTILT60%) and 2% (i.e., sham conditions CWTILT2% and CWTILT2%–ISO) of each participant's maximal inspiratory pressure. CWTILT60% and CWTILT2% were performed to exhaustion. CWTILT2%–ISO was interrupted at the time equal to that performed during CWTILT60%. * P < 0.05 between CWTILT2% and CWTILT60%; # P < 0.05 between CWTILT2%–ISO and CWTILT60%; † P < 0.05 between CWTILT2% and CWTILT2%–ISO. CWT, constant workload cycling tests; ILT, inspiratory loading task.