NEWLY DESIGHED MILITARY SUIT ON THERMAL STRAIN AND PHYSICAL PERFORMANCE

Manutsawee Sedsuwan, Metta Pinthong and Rungchai ChaunchaiyakulCollege of Sports Science and Technology, Mahidol University

Exercise in heat: Severe challenge

Heat, Fitness & Performance: Man can withstand large variations of environmental temp, while relatively small

increases in core temp (< 3oC) can lead to injury and even death uncompensation causes internal temperature reach the upper ‘safe’ limit within

10 min of moderate exercise intensity (Kenny and Johnson, 1992) Marathon performance declines 1-2 min for each 1 °C increase in air temperature

above 15 °C (Maughan, 2010) Aerobically fit individuals are able to perform for longer in hot environments, and

tolerate higher levels of hyperthermia than less fit individuals but Abnormally high core temperatures impair exercise performance in all individuals in

the heat, irrespective of fitness Fatigue generally occurs with core temperatures between 38 - 40 °C (Crandall &

Gonzalez, 2010).

C. G. Crandall and J. González-Alonso. Acta Physiol. 2010 ; 199(4): 407–423.

Maughan RJ. Scan.J.Med.Sci Sports. 2010, Suppl3:95-102.

Kenney WL, Johnson JM. Med Sci Sports Exerc. 1992; 24:303–312.

Performance Impairment

Sweating Dehydration

Cardiovascular Insufficiency

Vasodilatation

Overheating Impaired Performance

Coyle. Sports Sci Exchange. 1991;4:34.

Commercial Clothing

Investigators Study group Conditions Findings

Kwon et al., 1998. sedentary 100% Polyester, wool/long sleeve,Cycle 10 min at 32 W,

34๐C, 63%RH

↔ Skin Temp.↑ Heat storage↑ Core temp.

Dai et al. (2008) sedentary 100% Polyester, 52% wool,

Exerc at 70% VO2max, 30 min,

32๐C, 20%RH

↔ Heart rate,↔ Skin temp.↔ Core temp

Gavin et al. (2001) sedentary Synthetic material, 100%cotton/Short sleevesExerc at 70% VO2max, 30 min

30๐C, 35% RH

↔ Heart rate,↔ Skin temp.,↔ Core temp.,

↔ VO2

Clothing should be Lightweight Light in colour Breathable/open weave

Loose Absorbent Assist sweat evaporation

Missions under Extreme Environment

Military clothing

Long and short sleeve battle dress uniform

Total weight: 15-25 kg.

Cover about 22% of body surface area.

Hadid et al, 2008; Chinevere et al, 2008

Protective Military T-Shirts

Investigators Study group Conditions Findings

Cadarette et al, 2001 Elite athletes New modular body design (open shoulder and collar)

Exerc: walking, 100 min on a treadmillAt 40 ๐C, 20% rh

core temp, heart rate

Cheuvront et al, 2008.

Active men Protective vest,Exerc: 50 min walk/10 min rest * 4 hrs

At 35 ๐C, 30% RH

↑ core temp, ↑ heart rate

Chinevere et al. 2008

Sedentary Ventilated vest,Exerc: 2-h treadmill at 200 W.m-2

At 40 ๐C, 20% RH

↑ core temp, ↑ heart rate

after 1 hr

Barwood, et al 2009.

Active men Wearing the vest, blowing ambient air around the torso for 10 days

Exerc: walked on a treadmill (5 km/h, 2% incline)

At 45๐C, 10% RH

↓ core temp, ↑ heart rate, RPE,

↑ performance 18%

Problem with the climate

Problem within the body

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2OH2O

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2OH2O

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2OH2O

H2O

H2O

H2O

H2O

H2O

Evaporation

Radiation

Convection

Conduction

H2O

For a man, 70 kg, BSA approx 1.8 m2

His uncovered facial area approx 0.14-0.2 m2

New military suit has been designed for better heat exchange!

Purposes of study

- To study the effects of newly designed military shirt on physiological functions during exercise under hot condition

Hypothesis

- Wearing a military shirts (old style, CON and new designed, NMS) would differently affected on exercise tolerance under hot-humid condition.

Participants

Inclusion criteria

- Healthy military men, age between 18 – 25 yrs

- BMI in normal ranges

- Regularly trained at least 3 months

- VO2max > 40 ml/kg/min

Exclusion criteria

- Joint, muscle, cardiovascular and respiratory diseases

- Problems of GI tract, Gag reflex

Termination criteria

- can not sustain 60 min exercise continuously.

- Core temperature > 39.5 ๐C.

- Voluntarily stop

10 military men

Variables

Anthropometry: Ages, Weight, Height, BMI, % Fat, RHR, BP, VO2max (Treadmill, Bruce)

Thermoregulatory system: Core temp, Skin temp (left side, forearm, chest, back, thigh and calf; Ramanathan 1964)

Cardiovascular system: Heart rate (HR), Stroke volume (SV), Cardiac output (CO)

Metabolic system: Oxygen Consumption (VO2), Carbon dioxide production (VCO2), Respiratory exchange ratio (RER), Tidal volume (VT), Minute ventilation (VE), Respiratory rate (RR)

Subjective evaluation: Rating of perceived Exertion (RPE), Thermal sensation scale (TSS), Thermal discomfort scale (TDS)

Cor Temp® Temperature Sensor

Rating perceived exertion (RPE) Thermal sensation scale (TSS) Thermal discomfort scale (TDS) Rating perceived exertion (RPE) Thermal sensation scale (TSS) Thermal discomfort scale (TDS)

Rating perceived exertion (RPE) Thermal sensation scale (TSS) Thermal discomfort scale (TDS)

Subjective Variables

Experimental protocol

Visit 1

AnthropometryVO2max

Visit 2 Visit 3

Cross-over, randomized

1 wk ap

art

1 wk ap

art

35oC, 50%RH

50 ml water * 6 50 ml water * 6

3.5 km/hr, 0 grade, 60 min 3.5 km/hr, 0 grade, 60 minBruce’s protocol

USGExerc tolerance

ThermoregCVS

MetabSubjective

-The normal distribution: Shapiro-Wilk W test. Main effects of shirt types (CON vs. NMS) and time: Two-way (time × trial) repeated-measures ANOVA. Statistical significance will be set at P < 0.05.

USGExerc tolerance

ThermoregCVS

MetabSubjective

CONor

NMS

Table 2. Averaged room temperatures and % relative humidity during two experimental conditions (means, SD).

Variables CONTROL (CON) New Military Shirt (NMS)

Room temperature (◦C) 35.18 ±0.35 35.20 ±0.24

Relative humidity () 49.71 ±3.19 49.84 ±4.70

Results: Table 1. General characteristics of subjects (n = 10).

Variables Mean +SD Age (yrs) 20.7 ±1.1 Body weight (kg) 65.4 ±6.2 Height (cm) 172.8 ±5.5 Body mass index (kg/m2) 22.3 ±1.7 %Fat 13.7 ±3.4 Max.oxygen consumption )ml/min/kg) 42.9 ±4.4 Resting heart rate (bpm) 72.9 ±8.3 Systolic BP (mmHg) 125.1 ±12.2 Diastolic BP (mmHg) 71.5±6.3

Table 3. Averaged core temperatures at rest and after exercise, exercise tolerance duration and total sweat loss (means, SEM).

Variables CON NMS Resting core temperature (◦C) 37.13 ±0.05 37.24 ±0.27 Post-exercise core temperature (◦C) 38.43 ±0.13 38.23 ±0.18 Exercise tolerance time (min)* 58.25 ±4.07 56.58 ±3.94 Total sweat loss (L) 1.34 ±0.13 1.49 ±0.12

* voluntarily stopped.

Results: Cardiorespiratory

RP

E (

6-20

)

minutes

CONNMS

RPE

VO

2(m

l/m

in)

VO2

minutes

CONNMS

VE

minutes

VE

(L/m

in)

CONNMS

HR

HR

(b

pm

)

CONNMS

Results: Skin & Core Temperatures

3434.5

3535.5

3636.5

3737.5

3838.5

39

1 2 3 4 5 6 7 8 9

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

calf back

arm thigh

chest

arm

tem

p. (

o C

)

thig

h te

mp.

(o

C)

core

tem

p. (

o C

)

ches

t tem

p. (

o C

)ca

lf te

mp.

(o

C)

back

tem

p. (

o C

)

CONNMS

37

37.2

37.4

37.6

37.8

38

38.2

38.4

1 2 3 4 5 6 7 8 9

coreCONNMS

**

*

*

**

*

*

3434.5

3535.5

3636.5

3737.5

3838.5

39

1 2 3 4 5 6 7 8 934

34.535

35.536

36.537

37.538

38.539

1 2 3 4 5 6 7 8 9

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

calf back

arm thigh

chest

arm

tem

p. (

o C

)

thig

h te

mp.

(o

C)

core

tem

p. (

o C

)

ches

t tem

p. (

o C

)ca

lf te

mp.

(o

C)

back

tem

p. (

o C

)

CONNMS

CONNMS

core

**

*

*

**

*

*

3434.5

3535.5

3636.5

3737.5

3838.5

39

1 2 3 4 5 6 7 8 934

34.535

35.536

36.537

37.538

38.539

1 2 3 4 5 6 7 8 9

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

5 10 15 20 25 30 35 40 45

minutes

calf back

arm thigh

chest

arm

tem

p. (

o C

)

thig

h te

mp.

(o

C)

core

tem

p. (

o C

)

ches

t tem

p. (

o C

)ca

lf te

mp.

(o

C)

back

tem

p. (

o C

)

CONNMS

CONNMS

core

**

*

*

**

*

*

Results: Subjective evaluations

0

0.5

1

1.5

2

2.5

3

3.5

4

1 2 3 4 5 6 7 8 9

5

7

9

11

13

15

17

19

1 2 3 4 5 6 7 8 9

5 10 15 20 25 30 35 40 45

minutes

TSS

TSS

CONNMS

CONNMS

RPE

RP

E

Conclusion

• Exercises in the heat with newly designed military suit exhibit– Similar cardiorespiratory stresses, as well as subjective evaluations– Lower core and skin temperatures at the back– Exercise termination durations (voluntary) were the same– Subjective evaluations were the same.

• With limited sample size, NMS offers some positive outcomes during exercise under the heat, at least it lowers core temperature which possibly be related to back region

THANK YOU FORYOUR ATTENTION

References

• Barwood, Phillip et al. Ventilated vest and tolerance for intermittent exercise in hot, dry conditions with military clothing. Aviat Space Environ Med 2009;80:353-9.

• C. G. Crandall and J. González-Alonso. Cardiovascular function in the heat-stressed human. Acta Physiol (Oxf). 2010 August ; 199(4): 407–423.

• Cheuvront, Goodman et al. Impact of a protective vest and spacer garment on exercise - heat strain. Eur J Appl Physiol 2008: 102:577-583.

• Chinevere, Cadarette, et al. Efficacy of body ventilation system for reducing strain in warm and hot climates. Eur J Appl Physiol 2008:103:307-314.

• Coyle EF. Cardiovascular function during exercise: neural control factors. Sports Sci Exchange. 1991;4:34.• Dai, et al. Effect of moisture transport on microclimate under T-shirt. Eur J Appl Physiol 2008;104(2), 337-340.• Gavin, et al. Clothing fabric does not affect thermoregulation during exercise in moderate heat. Medicine and Science in

Sports and Exercise 2001; 33(12): 2124-2130.• Kenney WL, Johnson JM. Control of skin blood flow during exercise. Med Sci Sports Exerc. 1992; 24:303–312. • Kwon, Kato, Kawamura, Yanai & Tokura. physiological significance of hydrophilic Textile materials during intermittent

exercise in humans under the influence of warm ambient temperature with and without wind. Eur J Appl Physiol 1998;78:487-493.

• Maughan RJ. Distance running in hot environments: a thermal challenge to the elite runner. Scan.J.Med.Sci Sports. 2010, Suppl3:95-102.

• Rowell LB, O'Leary DS, Kellogg DL. Integration of cardiovascular control systems in dynamic exercise. In: Rowell LB, Shepherd JT, eds. Exercise: Regulation and Integration of Multiple Systems. New York, NY: Oxford University Press; 1996:770-738.

• Tatterson, A. J., Hahn, et al. Effects of heat stress on physiological response and exercise performance in elite cyclists. Journal of Science and Medicine in Sport 2000;3(2): 186-193.