Category Nuances for null:

• local,
• positive,
• actual,
• routine,
• healthy,
• extracurricular,
• minor,
• new,
• animal,
• solitary,
• regular,
• preventative,
• physical,
• outdoor,
• personal,
• pleasurable,
• dynamic,
• usual,
• everyday,
• planned,
• natural,
• increased,
• metabolic,
• rhythmic,
• incidental,
• favorite,
• miscellaneous,
• familiar,
• innocuous,
• meaningful,
• enjoyable,
• informal,
• important,
• preventive,
• strenuous,
• cardiovascular,
• efficient,
• external,
• beneficial,
• normal,
• individual,
• extreme,
• basic,
• physiologic,
• crucial,
• indoor,
• corporate,
• joint,
• common,
• heavy,
• compulsive,
• stimulating,
• alternative,
• complex,
• appropriate,
• recreational,

Simple Categories for null:

• exertion,
• behavior,
• process,
• training,
• activity,
• outlet,
• task,
• effort,
• measure,
• behaviour,
• thing,
• event,
• practice,
• action,
• recreation,
• care,
• exercise,
• preparation,
• project,
• work,