***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Whole-body active warm-ups ( AWU ) and inspiratory muscle warm-up ( IMW ) prior to exercise improves performance on some endurance exercise tasks . This study investigated the effects of AWU with and without IMW upon 2.4-km running time-trial performance while carrying a 25-kg backpack , a common task and backpack load in physically dem and ing occupations . Participants ( n = 9 ) performed five 2.4-km running time-trials with a 25-kg thoracic load preceded in r and om order by ( i ) IMW comprising 2 × 30 inspiratory efforts against a pressure-threshold load of 40 % maximal inspiratory pressure ( PImax ) , ( ii ) 10-min unloaded running ( AWU ) at lactate turnpoint ( 10.33 ± 1.58 km·h-1 ) , ( iii ) placebo IMW ( PLA ) comprising 5-min breathing using a sham device , ( iv ) AWU+IMW , and ( v ) AWU+PLA . Pooled baseline PImax was similar between trials and increased by 7 % and 6 % following IMW and AWU+IMW ( P < 0.05 ) . Relative to baseline , pooled PImax was reduced by 9 % after the time-trial , which was not different between trials ( P > 0.05 ) . Time-trial performance was not different between any trials . Whole-body AWU and IMW performed alone or combination have no ergogenic effect upon high-intensity , short- duration performance when carrying a 25-kg load in a backpack Fatigue of the respiratory muscles during intense exercise might compromise leg blood flow , thereby constraining oxygen uptake ( Vo(2 ) ) and limiting exercise tolerance . We tested the hypothesis that inspiratory muscle training ( IMT ) would reduce inspiratory muscle fatigue , speed Vo(2 ) kinetics and enhance exercise tolerance . Sixteen recreationally active subjects ( mean + or - SD , age 22 + or - 4 yr ) were r and omly assigned to receive 4 wk of either pressure threshold IMT [ 30 breaths twice daily at approximately 50 % of maximum inspiratory pressure ( MIP ) ] or sham treatment ( 60 breaths once daily at approximately 15 % of MIP ) . The subjects completed moderate- , severe- and maximal-intensity " step " exercise transitions on a cycle ergometer before ( Pre ) and after ( Post ) the 4-wk intervention period for determination of Vo(2 ) kinetics and exercise tolerance . There were no significant changes in the physiological variables of interest after Sham . After IMT , baseline MIP was significantly increased ( Pre vs. Post : 155 + or - 22 vs. 181 + or - 21 cmH(2)O ; P < 0.001 ) , and the degree of inspiratory muscle fatigue was reduced after severe- and maximal-intensity exercise . During severe exercise , the Vo(2 ) slow component was reduced ( Pre vs. Post : 0.60 + or - 0.20 vs. 0.53 + or - 0.24 l/min ; P < 0.05 ) and exercise tolerance was enhanced ( Pre vs. Post : 765 + or - 249 vs. 1,061 + or - 304 s ; P < 0.01 ) . Similarly , during maximal exercise , the Vo(2 ) slow component was reduced ( Pre vs. Post : 0.28 + or - 0.14 vs. 0.18 + or - 0.07 l/min ; P < 0.05 ) and exercise tolerance was enhanced ( Pre vs. Post : 177 + or - 24 vs. 208 + or - 37 s ; P < 0.01 ) . Four weeks of IMT , which reduced inspiratory muscle fatigue , result ed in a reduced Vo(2 ) slow-component amplitude and an improved exercise tolerance during severe- and maximal-intensity exercise . The results indicate that the enhanced exercise tolerance observed after IMT might be related , at least in part , to improved Vo(2 ) dynamics , presumably as a consequence of increased blood flow to the exercising limbs The purpose was to determine the effect of moderate-intensity exercise training ( ET ) on inspiratory muscle fatigue ( IMF ) and if an additional inspiratory load during ET ( ET+IL ) would further improve inspiratory muscle strength , IMF , and time-trial performance . 15 subjects were r and omly divided to ET ( n=8 ) and ET+IL groups ( n=7 ) . All subjects completed six weeks of exercise training three days/week at ∼70%V̇O2peak for 30min . The ET+IL group breathed through an inspiratory muscle trainer ( 15 % PImax ) during exercise . 5-mile , and 30-min time-trials were performed pre-training , weeks three and six . Inspiratory muscle strength increased ( p<0.05 ) for both groups to a similar ( p>0.05 ) extent . ET and ET+IL groups improved ( p<0.05 ) 5-mile time-trial performance ( ∼10 % and ∼18 % ) and the ET+IL group was significantly faster than ET at week 6 . ET and ET+IL groups experienced less ( p<0.05 ) IMF compared to pre-training following the 5-mile time-trial . In conclusion , these data suggest ET leads to less IMF , ET+IL improves inspiratory muscle strength and IMF , but not different than ET alone Inspiratory threshold loading ( ITL ) induces cortical activation . It is sustained over time and is resistant to distraction , suggesting automaticity . We hypothesized that ITL-induced changes in cerebral activation may differ between single-breath ITL and continuous ITL , with differences resembling those observed after cortical automatization of motor tasks . We analyzed the brain blood oxygen level dependent ( BOLD ) signal of 11 naive healthy volunteers during 5 min of r and om , single-breath ITL and 5 min of continuous ITL . Single-breath ITL  increased BOLD in many areas ( premotor cortices , bilateral insula , cerebellum , reticular formation of the lateral mesencephalon ) and decreased BOLD in regions co-localizing with the default mode network . Continuous ITL induced signal changes in a limited number of areas ( supplementary motor area ) . These differences are comparable to those observed before and after overlearning of motor tasks . We conclude that the respiratory-related cortical activation observed in response to ITL is likely due to automated , attention-independent mechanisms . Also , ITL activates cortical circuits right from the first breath Inspiratory muscle training ( IMT ) has been shown to improve time trial performance in competitive athletes across a range of sports . Surprisingly , however , the effect of specific IMT on surface swimming performance remains un-investigated . Similarly , it is not known whether any ergogenic influence of IMT upon swimming performance is confined to specific race distances . To determine the influence of IMT upon swimming performance over 3 competitive distances , 16 competitive club-level swimmers were assigned at r and om to either an experimental ( pressure threshold IMT ) or sham IMT placebo control group . Participants performed a series of physiological and performance tests , before and following 6 weeks of IMT , including ( 1 ) an incremental swim test to the limit of tolerance to determine lactate , heart rate and perceived exertion responses ; ( 2 ) st and ard measures of lung function ( forced vital capacity , forced expiratory volume in 1 s , peak expiratory flow ) and maximal inspiratory pressure ( MIP ) ; and ( 3 ) 100 , 200 and 400 m swim time trials . Training utilised a h and -held pressure threshold device and consisted of 30 repetitions , twice per day . Relative to control , the IMT group showed the following percentage changes in swim times : 100 m , −1.70 % ( 90 % confidence limits , ±1.4 % ) , 200 m , −1.5 % ( ±1.0 ) , and 400 m , 0.6 % ( ±1.2 ) . Large effects were observed for MIP and rates of perceived exertion . In conclusion , 6 weeks of IMT has a small positive effect on swimming performance in club-level trained swimmers in events shorter than 400 Inspiratory muscle training ( IMT ) has consistently been shown to reduce exertional dyspnea in health and disease ; however , the physiological mechanisms remain poorly understood . A growing body of literature suggests that dyspnea intensity can be explained largely by an awareness of increased neural respiratory drive , as measured indirectly using diaphragmatic electromyography ( EMGdi ) . Accordingly , we sought to determine whether improvements in dyspnea following IMT can be explained by decreases in inspiratory muscle electromyography ( EMG ) activity . Twenty-five young , healthy , recreationally active men completed a detailed familiarization visit followed by two maximal incremental cycle exercise tests separated by 5 wk of r and omly assigned pressure threshold IMT or sham control ( SC ) training . The IMT group ( n = 12 ) performed 30 inspiratory efforts twice daily against a 30-repetition maximum intensity . The SC group ( n = 13 ) performed a daily bout of 60 inspiratory efforts against 10 % maximal inspiratory pressure ( MIP ) , with no weekly adjustments . Dyspnea intensity was measured throughout exercise using the modified 0 - 10 Borg scale . Sternocleidomastoid and scalene EMG was measured using surface electrodes , whereas EMGdi was measured using a multipair esophageal electrode catheter .  IMT significantly improved MIP ( pre : -138 ± 45 vs. post : -160 ± 43 cmH2O , P < 0.01 ) , whereas the SC intervention did not . Dyspnea was significantly reduced at the highest equivalent work rate ( pre : 7.6 ± 2.5 vs. post : 6.8 ± 2.9 Borg units , P < 0.05 ) , but not in the SC group , with no between-group interaction effects . There were no significant differences in respiratory muscle EMG during exercise in either group . Improvements in dyspnea intensity ratings following IMT in healthy humans can not be explained by changes in the electrical activity of the inspiratory muscles . NEW & NOTEWORTHY Exertional dyspnea intensity is thought to reflect an increased awareness of neural respiratory drive , which is measured indirectly using diaphragmatic electromyography ( EMGdi ) . We examined the effects of inspiratory muscle training ( IMT ) on dyspnea , EMGdi , and EMG of accessory inspiratory muscles . IMT significantly reduced submaximal dyspnea intensity ratings but did not change EMG of any inspiratory muscles . Improvements in exertional dyspnea following IMT may be the result of nonphysiological factors or physiological adaptations unrelated to neural respiratory drive ABSTRACT This study was conducted to determine the effects of inspiratory muscle training ( IMT ) on respiratory and peripheral muscles oxygenation during a maximal exercise tolerance test and on repeated-sprint ability ( RSA ) performance in professional women football players . Eighteen athletes were r and omly assigned to one of the following groups : SHAM ( n = 8) or IMT ( n = 10 ) . After a maximal incremental exercise test , all participants performed ( on a different day ) a time-to-exhaustion ( Tlim ) test . Peripheral and respiratory muscles oxygenation by near-infrared spectroscopy , breath-by-breath ventilatory and metabolic variables , and blood lactate concentration were measured . The RSA test was performed on a grass field . After a 6 week intervention , all athletes were reevaluated . Both groups showed increases in inspiratory muscles strength , exercise tolerance and RSA performance , however only the IMT group presented lower deoxyhemoglobin and total hemoglobin blood concentrations on intercostal muscles concomitantly to an increased oxyhemoglobin and total hemoglobin blood concentrations on vastus lateralis muscle during Tlim . In conclusion , these results may indicate the potential role of IMT to attenuate inspiratory muscles metaboreflex and consequently improve oxygen and blood supply to limb muscles during high-intensity exercise , with a potential impact on inspiratory muscle strength , exercise tolerance and sprints performance in professional women football players We have recently demonstrated that changes in the work of breathing during maximal exercise affect leg blood flow and leg vascular conductance ( C. A. Harms , M. A. Babcock , S. R. McClaran , D. F. Pegelow , G. A. Nickele , W. B. Nelson , and J. A. Dempsey . J. Appl . Physiol . 82 : 1573 - 1583 , 1997 ) . Our present study examined the effects of changes in the work of breathing on cardiac output ( CO ) during maximal exercise . Eight male cyclists [ maximal O2 consumption ( VO2 max ) : 62 + /- 5 ml . kg-1 . min-1 ] performed repeated 2.5-min bouts of cycle exercise at VO2 max . Inspiratory muscle work was either 1 ) at control levels [ inspiratory esophageal pressure ( Pes ) : -27.8 + /- 0.6 cmH2O ] , 2 ) reduced via a proportional-assist ventilator ( Pes : -16.3 + /- 0.5 cmH2O ) , or 3 ) increased via resistive loads ( Pes : -35.6 + /- 0.8 cmH2O ) . O2 contents measured in arterial and mixed venous blood were used to calculate CO via the direct Fick method . Stroke volume , CO , and pulmonary O2 consumption ( VO2 ) were not different ( P > 0.05 ) between control and loaded trials at VO2 max but were lower (-8 , -9 , and -7 % , respectively ) than control with inspiratory muscle unloading at VO2 max . The arterial-mixed venous O2 
    Output:
    
Recent evidence confirms the ergogenic effects of RMT and explores different loading protocol s , such as concurrent exercise and RMT ( i.e. , “ functional ” RMT ) .
These studies suggest that adapting new training protocol s may have an additive improvement effect , but evidence of the efficacy of such an approach is conflicting thus far .
Importantly , changes in ventilatory efficiency , oxygen delivery , cytokine release , motor recruitment patterns , and respiratory muscle fatigue resistance are highlighted as potential mechanistic factors linking RMT with performance improvements .