I maintain a resource center for plus sized riders (not that you are plus sized!) and I ran an article called "How Big is Too Big?- The Great Weight Debate" where I touch upon the weight bearing capacity of horses. Here is a summation of my article:
Scientific studies show that horses can safely carry 20% of their body weight with little indication of stress, while horses who carries 25-30% of their body weights experiences higher heart rates, faster breathing, and more muscle soreness and tightness. The article concludes that a 1200lb horse would be best suited for carrying no more than 240lbs of tack and rider.
Other research demonstrates the importance of equine fitness in correlation with weight bearing capacity, concluding that the standard for a horse is to carry 20% of it’s body weight safely, but it is strongly suggested that “it depends” on factors such as the horses health, overall fitness level, and type and duration of riding he is used for.
I have another article coming up next week called "How to detect lamness in your horse" where we go over ways to make sure your horse is sound with proper fitting tack to prevent lameness potentially caused or exacerbated by a rider's weight. Briefly:
- Look for non-specific signs
- Look at the whole horse
- Watch your horse move
- Listen to your horse's footfalls
- Feel for under saddle clues
- Observe your horses feet
I think at 155 pounds your horse is MORE than capable of carrying you, but if you have cause for concern check your tack for proper fit and keep him/her well conditioned to avoid potential soundness issues. It is nice to see owners who are respectful of the horses well-being!