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Effect of inspiratory muscle work on peripheral fatigue of locomotor muscles in healthy humans
Author(s) -
Romer Lee M.,
Lovering Andrew T.,
Haverkamp Hans C.,
Pegelow David F.,
Dempsey Jerome A.
Publication year - 2006
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2005.099697
Subject(s) - medicine , muscle fatigue , peripheral , cardiology , physical medicine and rehabilitation , electromyography , physical therapy
The work of breathing required during maximal exercise compromises blood flow to limb locomotor muscles and reduces exercise performance. We asked if force output of the inspiratory muscles affected exercise‐induced peripheral fatigue of locomotor muscles. Eight male cyclists exercised at ≥ 90% peak O 2 uptake to exhaustion (CTRL). On a separate occasion, subjects exercised for the same duration and power output as CTRL (13.2 ± 0.9 min, 292 W), but force output of the inspiratory muscles was reduced (−56% versus CTRL) using a proportional assist ventilator (PAV). Subjects also exercised to exhaustion (7.9 ± 0.6 min, 292 W) while force output of the inspiratory muscles was increased (+80% versus CTRL) via inspiratory resistive loads (IRLs), and again for the same duration and power output with breathing unimpeded (IRL‐CTRL). Quadriceps twitch force ( Q tw ), in response to supramaximal paired magnetic stimuli of the femoral nerve (1–100 Hz), was assessed pre‐ and at 2.5 through to 70 min postexercise. Immediately after CTRL exercise, Q tw was reduced −28 ± 5% below pre‐exercise baseline and this reduction was attenuated following PAV exercise (−20 ± 5%; P < 0.05). Conversely, increasing the force output of the inspiratory muscles (IRL) exacerbated exercise‐induced quadriceps muscle fatigue ( Q tw =−12 ± 8% IRL‐CTRL versus −20 ± 7% IRL; P < 0.05). Repeat studies between days showed that the effects of exercise per se , and of superimposed inspiratory muscle loading on quadriceps fatigue were highly reproducible. In conclusion, peripheral fatigue of locomotor muscles resulting from high‐intensity sustained exercise is, in part, due to the accompanying high levels of respiratory muscle work.