Volume 2 Supplement 1

Neural Control of Breathing

Open Access

Associative conditioning of the exercise ventilatory response in humans

  • W Al-Harbi1,
  • JC Coates1 and
  • JW Reed1
Respiratory Research20012(Suppl 1):P25

https://doi.org/10.1186/rr142

Received: 2 August 2001

Published: 17 August 2001

In goats, repeated exposure to moderate steady-state exercise with an added deadspace has been shown to alter the ventilatory response to subsequent exercise tests [1], a phenomenon termed long-term modulation (LTM). There are few relevant studies in humans, but it has been proposed that LTM can be achieved by a form of associative conditioning involving exercise and hypercapnia [2]. However, such data as there is would appear to be conflicting [3,4]. We have further investigated this phenomenon in humans in an attempt to resolve the disparity.

After providing informed consent as approved by the Local Ethics Committee, and familiarisation, 16 subjects (9 female, age 22.4 ± 2.7 years) were randomly divided into two groups; a control group (8 subjects, 5 female) and an intervention group (8 subjects, 4 female).

The Intervention protocol consisted an initial (pre) steady-state exercise bout (100 W, 5 min) on a cycle ergometer, followed by a 'conditioning session' of 10 repeated bouts of steady-state exercise (100 W) while breathing through an additional deadspace (+VD = 1.35 l). Two post-conditioning steady-state exercise tests (100 W, 5 min) were performed, one 7 min after (post1) and one 1 h after (post2) the end of the last conditioning bout. Each bout was interposed by a 7-min period of unencumbered rest.

The control group protocol was identical to the Intervention protocol, except that at no time was exercise associated with an added deadspace.

Breath-by-breath recordings for ventilatory parameters and respired gases (including PetCO2) were measured during exercise (Morgan Benchmark, Kent). The results are given in Table 1.
Table 1

Changes in exercise response following conditioning.

 

Intervention

Control

 

Pre vs Post1

Pre vs Post2

Pre vs Post1

Pre vs Post2

ΔVE (%)

-2.92

-4.95

-0.62

1.33

ΔfR (%)

12.85

9.06

11.13

8.47

ΔVT (%)

-11.31

-12.30

-10.63§

-7.16§

ΔPetCO2 (mmHg)

-1.67

-1.30

-1.72

-1.92

P < 0.05; P < 0.01; § P = 0.07.

Post-conditioning ventilation was not augmented in either group. Respiratory frequency was increased significantly in both groups post-conditioning, whilst both tidal volume and PetCO2 were reduced in both groups. The magnitude of the changes in the pattern of breathing and the PetCO2 were similar between groups at both post-conditioning assessments. The mechanisms underlying these changes are not immediately obvious, but the results do not support the concept of a LTM of exercise ventilation dependant on associative conditioning.

Authors’ Affiliations

(1)
Department of Physiological Sciences, University of Newcastle

References

  1. Martin PA, Mitchell GS: Long-term modulation of the exercise ventilatory response in goats. J Physiol. 1993, 470: 601-617.PubMedPubMed CentralView ArticleGoogle Scholar
  2. Turner DL, Bach KB, Martin PA, Olsen EB, Brownfield M, Foley KT, Mitchell GS: Modulation of ventilatory control during exercise. Respir Physiol. 1997, 110: 277-285. 10.1016/S0034-5687(97)00093-5.PubMedView ArticleGoogle Scholar
  3. Adams L, Moosavi SH, Guz A: Ventilatory response to exercise in man increases by prior conditioning of breathing with added deadspace. Am Rev Respir Dis. 1992, 145: A882-View ArticleGoogle Scholar
  4. Cathcart AJ, Herrold N, Turner AP, Wilson J, Ward SA: Absence of long-term modulation in response to external dead space loading during moderate exercise in humans. J Physiol. 2000, 528: 44-Google Scholar

Copyright

© BioMed Central Ltd 2001

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