Fig 1.
Inspiratory muscle strength testing to fatigue on a study subject.
Fig 2.
Training mask with a resistance valve inserted.
Fig 3.
Training mask on a study subject with a resistance valve in place.
Fig 4.
Incremental breath-loading protocol used for the respiratory muscle strength test to fatigue.
Blue bars indicate low-resistance recovery breaths while red bars represent an increasing load of high-resistance breaths (modified from Allen et al., 2019).
Table 1.
Summary of a group of Thoroughbred horses (n = 20) at the time of placement into an inspiratory muscle training treatment (n = 10) or control (n = 10) group based on when they finished exercise training and their current exercise workload.
Table 2.
The number of study horses at each exercise level in the inspiratory muscle training (IMT) treatment and control groups for each of the inspiratory muscle strength testing measurement time-points.
Table 3.
The average peak measured values from the inspiratory muscle strength test to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. *significantly different from T0. §significantly different from the Tr group.
Fig 5.
The average total number of inspiratory breaths achieved during inspiratory muscle strength testing to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. *significantly different from T0. **significantly different from the Tr group. T0: baseline, T1: after four weeks of IMT, T2: after eight weeks of IMT.
Fig 6.
The average peak inspiratory muscle strength index (IMSi) measurements from inspiratory muscle strength testing to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. *indicates significantly different from T0. **indicates significantly different from the Tr group. T0: baseline, T1: after four weeks of IMT, T2: after eight weeks of IMT.
Fig 7.
The average peak load measurements from inspiratory muscle strength testing to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. *indicates significantly different from T0. **indicates significantly different from the Tr group. T0: baseline, T1: after four weeks of IMT, T2: after eight weeks of IMT.
Fig 8.
The average peak power measurements from inspiratory muscle strength testing to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. T0: baseline, T1: after four weeks of IMT, T2: after eight weeks of IMT.
Fig 9.
The average peak volume measurements from inspiratory muscle strength testing to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. *indicates significantly different from T0. **indicates significantly different from the Tr group. T0: baseline, T1: after four weeks of IMT, T2: after eight weeks of IMT.
Fig 10.
The average peak flow measurements from inspiratory muscle strength testing to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. *indicates significantly different from T0. T0: baseline, T1: after four weeks of IMT, T2: after eight weeks of IMT.
Fig 11.
The average peak energy measurements from inspiratory muscle strength testing to fatigue for each time-point for n = 20 Thoroughbred horses in an inspiratory muscle training (IMT) treatment (Tr, n = 10) or control (Con, n = 10) group.
Data presented as mean ± SEM and analysed using a mixed linear model with P≤0.05 significant. *indicates significantly different from T0. **indicates significantly different from the Tr group. T0: baseline, T1: after four weeks of IMT, T2: after eight weeks of IMT.