title: Loading of trained inspiratory muscles speeds lactate recovery kinetics.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effects of inspiratory threshold loading (ITL) and inspiratory muscle training (IMT) on blood lactate concentration ([lac(-)]B) and acid-base balance after maximal incremental cycling.
  
  
  METHODS
  Eighteen subjects were divided into a control (n = 9) or an IMT group (n = 9). Before and after a 6-wk intervention, subjects completed two maximal incremental cycling tests followed by 20 min of recovery with (ITL) or without (passive recovery (PR)) a constant inspiratory resistance (15 cm H2O). The IMT group performed 6 wk of pressure threshold IMT at 50% maximal inspiratory mouth pressure. Throughout recovery, acid-base balance was quantified using the physicochemical approach by measuring the strong ion difference ([SID] = [Na+] + [K+] - [Cl-] + [lac-]), the total concentration of weak acids ([Atot-]), and the partial pressure of carbon dioxide (PCO2).
  
  
  RESULTS
  After the intervention, maximal inspiratory mouth pressure increased in the IMT group only (+34%). No differences in lactate clearance were observed between PR and ITL before the intervention in both groups and after the intervention in the control group. After IMT, relative to PR, [lac-]B was reduced throughout ITL (minutes 2-20) by 0.66 +/- 1.28 mmol x L(-1) (P < 0.05), and both the fast (lactate exchange) and the slow (lactate clearance) velocity constants of the lactate recovery kinetics were increased (P < 0.05). Relative to pre-IMT, ITL reduced plasma [H], which was accounted for by an IMT-mediated increase in [SID] due almost exclusively to a 1.7-mmol x L(-1) reduction in [lac-]B.
  
  
  CONCLUSIONS
  After maximal exercise, ITL affected lactate recovery kinetics only after IMT. Our data support the notion that the inspiratory muscles are capable of lactate clearance that increases [SID] and reduces [H+]. These effects may facilitate subsequent bouts of high-intensity exercise.
authors.affiliation: Optimal Performance Limited, Bristol, United Kingdom. peter@optimalperformance.co.uk
authors.forename: Peter I
authors.initials: PI
authors.lastname: Brown
authors.forename: Graham R
authors.initials: GR
authors.lastname: Sharpe
authors.forename: Michael A
authors.initials: MA
authors.lastname: Johnson
mesh_terms: D000140:Acidosis, Lactic / Q000517:prevention & control; D001642:Bicycling / Q000502:physiology*; D001784:Blood Gas Analysis; D001945:Breathing Exercises; D016022:Case-Control Studies; D005080:Exercise Test; D005541:Forced Expiratory Volume; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D010101:Oxygen Consumption; D012132:Respiratory Muscles / Q000502:physiology*; D055815:Young Adult
chemical_list: D019344:Lactic Acid