The effects of locomotor‐respiratory coupling on the pattern of breathing in horses.

Abstract

1. To investigate the effect of locomotor activity on the pattern of breathing in quadrupeds, ventilatory response was studied in four healthy horses during horizontal and inclined (7 %) treadmill exercise at different velocities (1 4-6-9 m s-1) and during chemical stimulation with a rebreathing method. Stride frequency (fe) and locomotor-respiratory coupling (LRC)were also simultaneously determined by means of video recordings synchronized with respiratory events. 2. Tidal volume (VT) was positively correlated with pulmonary ventilation (VE) but significantly different linear regression equations were found between the experimental conditions (P < 0 0001), since the chemical hyperventilation was mainly due to increases in VT, whereas the major contribution to exercise hyperpnoea came from changes in respiratory frequency (fR).3. The average fR at each exercise level was not significantly different from f", although therewas not always a tight 1: 1 LRC. At constant speeds, fs was independent of the treadmill slope and hence the greater VE during inclined exercise was due to increased VT. 4. At any ventilatory level, the differences in breathing patterns between locomotion and rebreathing or locomotion at different slopes derived from different set points of the inspiratory off-switch mechanism. 5. The percentage of single breaths entrained with locomotor rhythm rose progressively and significantly with treadmill speed (P < 0 0001) up to a 1: 1 LRC and was significantly affected by treadmill slope (P < 0 001). 6. A LRC of 1: 1 was systematically observed at canter (10 out of 10 trials) and sometimes at trot (5 out of 14) and it entailed (i) a 4-to 5-fold reduction in both VT and fR variability, and (ii) a gait-specific phase locking of inspiratory onset during the locomotor cycle. 7. It is concluded that different patterns of breathing are employed during locomotion and rebreathing due to the interference between locomotor and respiratory functions, which may play a role in the optimization and control of exercise ventilation in horses.

Centre of mass movement and mechanical energy fluctuation during gallop locomotion in the Thoroughbred racehorse

“…This effectively increases the CoM movement in the horizontal direction. Assuming a tidal volume of a galloping horse of about 10-15·l (Lafortuna et al, 1996) and a cross-sectional area of the thorax of about 0.25·m 2 , the diaphragm will move by about 0.05·m, which is slightly less than the observed displacement of the trunk. Ventilation should thus increase the actual fluctuation of the horizontal kinetic energy of the CoM relative to trunk movement and not contribute to a reduction of mechanical work.…”

“…Relative to its mean position the horse goes backward in the aerial phase and during early non-lead hind stance (Figs·4, 5). The onset of inspiration at canter is approximately seen some time between the end of the lead front leg stance phase and the beginning of the aerial phase (Attenburrow, 1982;Lafortuna et al, 1996). This effectively increases the CoM movement in the horizontal direction.…”

Coupling of breathing and movement during manual wheelchair propulsion.

“…At higher speeds, it switched to a 1:1 (monofrequency) ratio between stride frequency and respiratory frequency. The components of LRC were studied more extensively in another quadruped, the horse, which maintains a constant 1:1 ratio during the canter (slow gallop) and gallop (Bramble & Carrier, 1983;Lafortuna, Reinach, & Saibene, 1996). Human runners demonstrate more flexibility than quadrupeds, shifting from 4:1 (four strides per breath) to 2:1 with 1243 increased velocity and altering frequency ratios (e.g., 2:1,3:1,4:1,3:2, 5:2) during steady-state behavior (Bramble & Carrier, 1983).…”

Lungs And Legs: Entrainment Of Breathing To Locomotion In Highly Trained Distance Runners

“…While strict entrainment occurs in antelopes (Kamau, 1990), hopping wallabies (Baudinette et al, 1987), and in horses while running (Bramble & Carrier, 1983;Young et al, 1992) and cantering (Lafortuna et al, 1996), it occurs infrequently in cats while walking (Iscoe, 1981) and in rabbits at slow running speeds (Simons, 1999). Entrainment has also been shown to occur, sometimes infrequently or transiently, in humans while walking and running (Bechbache & Duffin, 1977;Bernasconi & Kohl, 1993;Berry et al, 1988;Bonsignore et al, 1998;Bramble & Carrier, 1983;Hill et al, 1988;McDermott et al, 2003;Paterson et al, 1987;Raßler & Kohl, 1996;Takano, 1995), cycling (Bechbache & Duffin, 1977;Bernasconi & Kohl, 1993;Bonsignore et al, 1998;Jasinskas et al, 1980;Paterson et al, 1986), rowing (Mahler et al, 1991), and even while walking with crutches (Hurst et al, 2001) ( Table 1).…”

“…Entrainment has also been shown to occur, sometimes infrequently or transiently, in humans while walking and running (Bechbache & Duffin, 1977;Bernasconi & Kohl, 1993;Berry et al, 1988;Bonsignore et al, 1998;Bramble & Carrier, 1983;Hill et al, 1988;McDermott et al, 2003;Paterson et al, 1987;Raßler & Kohl, 1996;Takano, 1995), cycling (Bechbache & Duffin, 1977;Bernasconi & Kohl, 1993;Bonsignore et al, 1998;Jasinskas et al, 1980;Paterson et al, 1986), rowing (Mahler et al, 1991), and even while walking with crutches (Hurst et al, 2001) ( Table 1). Animals that run on four legs seem to be constrained to a 1:1 ratio between steps and breaths, especially as speed increases (Boggs, 2002;Lafortuna et al, 1996;Simons, 1999 (Bramble & Carrier, 1983). On the other end of the locomotion spectrum is the sluggish terrestrial turtle, which seems to be the only animal studied that does not entrain breathing to stride rate (Landberg et al, 2003).…”