Pilot reported an off airport landing after engine power loss precluded an airport landing.

Narrative

On Date; I was receiving an aircraft check out in a Cessna 182P. Preflight inspection of the aircraft including the engine and engine oil was ordinary. The engine operation was also normal during start; taxi; runup; and takeoff. During each of those phases; various throttle positions including throttle full rearward to throttle full forward were typical with expected corresponding engine manifold and RPM indications. A normal crosswind takeoff was conducted at throttle full forward and engine operation during takeoff and climb indicated the engine was producing full power. The power was subsequently reduced to cruise setting after leveling off at 6;500 feet MSL before again increasing to full power for a step-climb to 7;500 feet MSL for airspace avoidance. Again; power indications on the second climb and level off to cruise were normal for the corresponding throttle positions. After clearing the area for traffic; the instructor asked me to perform a stall and recovery. To set up for the maneuver; the throttle was reduced to partial power to reduce airspeed. At some point during the maneuver the throttle was increased to full forward; however the engine remained at very low thrust and the engine was unresponsive to throttle control movement. An immediate turn towards ZZZ was commenced and a radio call requesting a full stop landing. An attempt was made to diagnose the problem during which we both confirmed we were no longer able to maintain altitude at a safe airspeed and [advised ATC] and landed in a field approximately 5 miles southwest of ZZZ1. Impressions: The throttle was moved to various positions during all phases prior to flight and no anomalies were noted. This included movements from full aft throttle to full forward. I do not believe any preflight check would have indicated an issue prior to throttle cable breakage. An A&P mechanic made a comment that it's difficult to inspect the throttle cable during routine maintenance. My recommendation would be the further investigation into the feasibility of inspecting the throttle cable for wear during maintenance.