$args = array('post_type'=>'bbfitness_exercises',
			'tax_query' => array(
					array(
						'taxonomy' => 'bbfitness_exercises_types',
						'field' => 'id',
						'terms' => $etype
					)
				)
		);				

		// The Query
		$the_query = new WP_Query( $args );
		$result = $the_query->posts;

When you create a custom post type and need to query by ID then you can pass in the 'field' and the 'terms' with the ID for that post type.

WordPress Query Taxonomy by ID

post, wordpress

PHP