AbstractHeat induced changes in aged bovine m. longissimus dorsi (LD) and m. biceps femoris (BF) were studied by water bath cooking to 60, 70 or 80°C at slow (.12°C/min) and fast (.6°C/min) heating rates. Forcedeformation curves from the Warner‐Bratzler (WB) shear device were used to evaluate specific changes in the myofibrillar (WB M‐force) and connective tissue component (WB C‐force) of tenderness. Other measurements include WB peak force value, cooking loss, collagen solubility and sensory evaluations. Differences due to muscle type were significant in all parameters except collagen solubility. Both WB M‐ and WB C‐force were reduced by slow heating rate but for samples heated to 80°C, WB M‐force was affected only by heating rate below 60°C while WB C‐force was most influenced above 60°C. Effect of final temperature resulted in higher WB M‐force from 60°C to 70°C, whereas WB C‐force was most affected from 70°C to 80°C. On the contrary, WB peak force was less affected by final temperature. Due to concomitant and opposing changes in myofibrillar and connective tissue strength with increasing end point temperature, it is concluded that improvements in interpretations with regard to heat‐induced changes and response of heat treatment in various muscles may be increased by measurement of WB M‐force and WB C‐force fr