Effects of training on maximum oxygen consumption of ponies

Objectives--To establish maximum oxygen consumption ((V) over dot O(2)max) in ponies of different body weights, characterize the effects of training o f short duration on (V) over dot O(2)max, and compare these effects to thos e of similarly trained Thoroughbreds. Animals--5 small ponies, amid-sized ponies, and 6 Thoroughbreds. Procedure--All horses were trained for 4 weeks. Horses were trained every o ther day for 10 minutes on a 10% incline at a combination of speeds equated with 40, 60, 80, and 100% of (V) over dot O(2)max. At the beginning and en d of the training program, each horse performed a standard incremental exer cise test in which (V) over dot O(2)max was determined. Cardiac output (Q), stroke volume (SV), and arteriovenous oxygen content difference (C [a-v] O -2) were measured in the 2 groups of ponies but not in the Thoroughbreds. Results--Prior to training, mean (V) over dot O(2)max for each group was 82 .6 +/- 2.9, 97.4 +/- 13.2, and 130.6 +/- 10.4 ml/kg/min, respectively. Foll owing training, mean (V) over dot O(2)max increased to 92.3 +/- 6,0, 107.8 +/- 12.8, and 142.9 +/- 10.7 ml/kg/min. Improvement in (V) over dot O(2)max was significant in all 3 groups. For the 2 groups of ponies, this improvem ent was mediated by an increase inQ; this variable was not measured in the Thoroughbreds, Body weight decreased significantly in the Thoroughbreds but not in the ponies, Conclusions and Clinical Relevance--Ponies have a lower (V) over dot O(2)max than Thoroughb reds, and larger ponies have a greater (V) over dot O(2)max than smaller po nies. Although mass-specific (V) over dot O(2)max changed similarly in all groups, response to training may have differed between Thoroughbreds and po nies, because there were different effects on body weight.