This is a complex question, but a common one.  Many injured and disabled employees keep working longer then they should, and do so for many reasons.  Sometimes it is financial pressure, or it may be the desire to keep doing what he or she always has after building a successful career.  Insurance companies often use those efforts to prove you are not really disabled.  However, insurance companies often overstate the significance of this evidence.  As the Court observed in Garcia v. Colum, 2013 U.S. App. LEXIS 25452 (7th Cir. December 20, 2013):

One can be employed full time without being capable of substantial gainful activity, paradox though that may seem. Gentle v. Barnhart, 430 F.3d 865 (7th Cir. 2005; Hawkins v. First UNUM Corp. LTD Plan, 326 F.3d 914 (7th Cir. 2003; Wilder v. Apfel, 153 F.3d 799 (7th Cir. 1998); Kelley v. Callahan, 133 F.3d 583 (8th Cir. 1998). The reasons given in the cases we’ve just cited are a desperate employee, or a lenient or altruistic employer. But another reason why a disabled employee might be treated by his employer as a full-time employee…

The Tenth Circuit (where Colorado is located) - - and several others - - have expressed the same sentiment.  As one Judge explained :  "A desperate person might force himself to work despite an illness that everyone agreed was totally disabling."; Levinson v. Reliance Standard Life Ins. Co., 245 F.3d 1321, 1326 (11th Cir. 2001) (full-time work status is not reliable evidence that he is able to perform the material duties of his occupation on a full-time basis).