Although not a form of breathing, the Valsalva maneuver involves the respiratory muscles. It is, in fact, a very forceful exhalatory effort against a tightly closed glottis , so that no air can escape from the lungs.  Instead abdominal contents are evacuated in the opposite direction, through orifices in the pelvic floor. The abdominal muscles contract very powerfully, causing the pressure inside the abdomen and thorax to rise to extremely high levels. The Valsalva maneuver can be carried out voluntarily, but is more generally a reflex elicited when attempting to empty the abdomen during, for instance, difficult defecation, or during childbirth. Breathing ceases during this maneuver.
Small business employers may contact OSHA's free and confidential On-Site Consultation program to help determine whether there are hazards at their worksites and work with OSHA on correcting any identified hazards. Consultants in this program from state agencies or universities work with employers to identify workplace hazards, provide advice on compliance with OSHA standards, and assist in establishing injury and illness prevention programs. On-Site Consultation services are separate from enforcement activities and do not result in penalties or citations. To contact OSHA's free consultation service, go to OSHA's On-Site Consultation web page or call 1-800-321-OSHA (6742) and press number 4.