Impact of a protective vest and spacer garment on exercise heat strain

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA477047&Location=U2&doc=GetTRDoc.pdf


Protective vests worn by global security personnel,
and weighted vests worn by athletes, may increase
physiological strain due to added load, increased clothing
insulation and vapor resistance. The impact of protective
vest clothing properties on physiological strain, and the
potential of a spacer garment to reduce physiological
strain, was examined. Eleven men performed 3 trials of
intermittent treadmill walking over 4 h in a hot, dry environment
(35C, 30% rh). Volunteers wore the US Army
battledress uniform (trial B), B + protective vest (trial P),
and B + P + spacer garment (trial S). Biophysical clothing
properties were determined and found similar to many law
enforcement, industry, and sports ensembles. Physiological
measurements included core (Tc), mean skin (Tsk) and chest
(Tchest) temperatures, heart rate (HR), and sweating rate
(SR). The independent impact of clothing was determined
by equating metabolic rate in all trials. In trial P, HR was
+7 b/min higher after 1 h of exercise and +19 b/min by the
fourth hour compared to B (P\0.05). Tc (+0.30C), Tsk
(+1.0C) and Physiological Strain Index were all higher in
P than B (P\0.05). S did not abate these effects except to
reduce Tsk (P[S) via a lower Tchest (-0.40C) (P\0.05).
SR was higher (P\0.05) in P and S versus B, but the
magnitude of differences was small. A protective vest
increases physiological strain independent of added load,
while a spacer garment does not alter this outcome.