If you hold down the run key while crouched you hear the heavy breathing and see the increased oxygen usage from running despite remaining crouched and moving at the same speed.
Good catch. Somehow I overlooked this. Will change this in probably the next update.
This should be resolved in v0.51. Thanks for the report.
This update is now available in v0.51 which you can download via your Humble library. If you have a chance to check the changes I'd love to hear your feedback. Thanks!
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