X hits on this document

PDF document

This article has been cited by 4 other HighWire hosted articles - page 5 / 7





5 / 7




37.02 0.06

36.90 0.10

36.67 0.15*


37.06 0.08

37.05 0.09

36.92 0.11


75 1.5*

72 1.4*

70 1.2*


67 2.2

65 1.9

63 1.6


136 13*

130 13*

132 15*


74 3

73 5

71 5


1.1 0.3*

0.6 0.3*

0.7 0.3*


2.0 0.2

1.9 0.2

1.9 0.2


3.1 0.2*

3.3 0.2*

3.3 0.2*


2.2 0.2

2.2 0.3

2.4 0.3

30 min

˙ HR, heart rate; M,

Thermal discomfort

body immersion; Tre, rectal temperature;

Table 2. Effect of lower body and head-out whole body cold-water immersion on core body temperature, heart rate, metabolic heat production, thermal sensation, and thermal discomfort at 10, 20, and 30 min of immersion

Values are means SE. LBI, lower body immersion; WBI, metabolic heat production. *Significant treatment differences

head-out whole , P 0.05.

Variable Tre, °C

HR, beats/min

˙ M, W/m2

Thermal sensation


10 min

20 min

by the two immersion techniques (11), with WBI ex- p o s i n g a p p r o x i m a t e l y t w i c e a s m u c h s k i n s u r f a c e a r e a . ˙ In cold air, increasing M may preserve core tempera-

Differential responses in temperature and metabo- l i s m b e t w e e n L B I a n d W B I r e s u l t e d i n s i g n i fi c a n t ˙ differences in S rates over the course of the experi-

t u r e b u t c a n n o t o f f s e t h e a t l o s s i n c o o l o r c o l d w a t e r ( 6 , ˙ 17). M during LBI was somewhat higher than reported

during thermoneutral conditions (73 W/m2 during LBI compared with 4049 W/m2) (19). Using the W e i r ( 2 4 ) e q u a t i o n , L e e e t a l . ( 1 7 ) r e p o r t e d s l i g h t l y ˙ lower M during resting immersion to the hip and neck

in 15 and 25°C than was observed in the present study. The differences between hip- and neck-level immersion at 15 and 25°C were 140˙and 40 W/m2, respectively (17). At 15°C, increased M during neck-level immer- sion was likely due to greater thermal afferent input and shivering induced by larger decreases in Tc. In the present study, a difference of 60 W/m2 between WBI and LBI was observed, which is consistent with the findings of Lee et al. for˙the 25°C immersion condition.

ment. WBI resulted in a significantly greater rate of heat loss˙during immersion and a significantly greater positive S rate during exercise compared with LBI (Fig. 2). However, the net effect of both immersion tech- niques was essentially the same when the negative and positive changes were balanced for the entire experi- ment. This is in contrast to our laboratorys previous work using the same exercise protocol preceded by either LBI precooling or no cooling (25). Although pre- c o o l i n g r e s u l t e d i n g r e a t e r r a t e s o f n e g a t i v e a n d p o s i - t i v e S ˙ d u r i n g i m m e r s i o n a n d e x e r c i s e , r e s p e c t i v e l y , n e t ˙ S over the course of the experiment was significantly

greater for the no-cooling condition (25). This higher heat gain corresponded to significantly higher Tre in the noncooled condition for the duration of exercise.

Smaller increases in M during LBI may be beneficial for some clinical populations. For example, MS pa- tients have limited physical capacity for work due to a c c u m u l a t e d d i s a b i l i t y a n d a b n o r m a l f a t i g u e , w h i c h i s ˙ worsened by increased Tb. The increase in M induced

by WBI is somewhat counterproductive to the purpose of precooling for individuals with MS, which is to facil- itate achievement of physical activities.

LBI and WBI produced different thermoregulatory responses during water immersion, but both treat- ments produced a significant reduction in Tre during the first minutes of exercise, although WBI resulted in a significantly larger reduction in Tre. In practical terms, both WBI and LBI treatments provided an ef- fective heat sink to lengthen the time to reach an increase in Tre of 0.5°C above baseline. During exer-



12.8 0.4

14.4 0.6

15.4 0.6

M, W/m2


419 15

396 38

439 14


10 min

20 min

30 min


139 3 135 2 13.1 0.6

155 3 150 3 14.1 0.6

164 3 160 3 15.1 0.6


382 13

412 22

432 20


1.4 0.2*

2.8 0.2*

3.8 0.2


1.9 0.2

3.3 0.2

4.1 0.2


4.9 0.4

5.8 0.3

6.2 0.3


5.4 0.2

6.3 0.1

6.7 0.1


1.7 0.2

2.3 0.1

2.7 0.2


2.0 0.2

2.5 0.3

2.9 0.3

Table 3. Effect of lower body and head-out whole body precooling on heart rate, rating of perceived exertion, m e t a b o l i c h e a t p r o d u c t i o n , s w e a t s e n s a t i o n , t h e r m a l s e n s a t i o n , a n d t h e r m a l d i s c o m f o r t ˙ during submaximal exercise at a workload corresponding to 60% VO2max

Variable HR, beats/min

RPE, 9-20 point scale

, P 0.05.

Sweat sensation

Thermal sensation

Thermal discomfort

Values are means SE. RPE, rating of perceived exertion. *Significant treatment differences

J Appl Physiol VOL 94 MARCH 2003 www.jap.org

Downloaded from on February 3, 2015

Document info
Document views20
Page views20
Page last viewedWed Jan 18 20:39:58 UTC 2017