Background: Both near and far infrared have shown interesting biological effects and have been suggested as new ergogenic aid to enhance sport performance. Although, some studies have
shown the utility of near infrared to improve strength and endurance performance; these results were obtained from phototherapy devices (LED or laser light), non-portable and fed by electric power. A
new technology can partly solve these issues; Far Infrared (FIR) emitting fabric (polyamide fiber mixed to emitting inorganic substances) is capable to absorb heat and re-emit this energy as FIR
radiation. It is known that FIR emitted by materials can enhance cell metabolism and function, improve blood circulation and an ex-vivo study of skeletal muscle have shown the effect of delay fatigue.
Although, FIR share in vitro findings of positive effects with near infrared; ergogenic effects of both forms of infrared have never been compared, as well as their mechanisms are not fully
understood. Furthermore, the effect of the FIR fabric on performance was poorly investigated. Thus, our study analyses the effect of FIR fabric on exercise bioenergetics and exercise tolerance during
moderated and very heavy intensity exercise.
Methods: Sixteen men (age 25.1+3.7 years; mass 69.8+7.4 kg, height 174.1+5.8 cm; VO2max 36.6+4.9 ml.kg-1.min-1; POmax 290,9+29,4 W) performed two testing days, two weeks apart,
composed by a square-wave cycling exercise at moderate intensity (2 sets of 10 min), followed by very heavy intensity (until exhaustion). Tests occurred after 96 hours of use of FIR or Placebo fabric,
in a crossover, double-blind, placebo-controlled design. The Total Energy Expenditure (TE) and the Aerobic Contribution (AC) (exercise oxygen uptake), Anaerobic Lactic Contribution (AnLC) (plasma
lactate accumulation) and Anaerobic Alactic Contribution (AnAC) (fast VO2 off-kinetics), absolute and relative to TE values, were calculated using the GEDAE-LaB software (http://gedaelab.org/).
Results: Total exercise time (Placebo 3326±84 s – FIR 3372±120 s, p=0.03). Absolute energy system contributions (kJ), for the moderate exercise: TE (Placebo 99.26±48.38 – FIR
97.09±48.85, p>0.05); AC (Placebo 87.32±41.44 – FIR 85.01±43.12, p>0.05); AnLC (Placebo 4.53±3.32 – FIR 4.61±3.65, p>0.05); AnAC (Placebo 7.40±4.90 – FIR 7.47±3.61, p>0.05). For the very heavy
exercise until exhaustion: TE (Placebo 204.19±90.02 – FIR 250.64±99.31, p=0.005); AC (Placebo 134.59±83.70 – FIR 174.12±93.58, p=0.004); AnLC (Placebo 41.90±9.13 – FIR 47.21±9.36, p=0.003); AnAC
(Placebo 27.70±27.43 – FIR 29.31±27.09, p>0.05). Relative energy system contributions (%), for the moderate exercise: AC (Placebo 88.52+3.17 – FIR 87.83+3.21, p>0.05); AnLC (Placebo 4.29+2.34 – FIR
4.45+2.88, p>0.05); AnAC (Placebo 7.18+2.47 – FIR 7.72+1.45, p>0.05). For the very heavy exercise until exhaustion: AC (Placebo 62.82+14.57 – FIR 67.64+11.01, p=0.06); AnLC (Placebo 22.75+6.88 – FIR
20.28+4.93, p=0.07); AnAC (Placebo 14.43+12.90 – FIR 12.08+9.86, p>0.05).
Conclusion: Far infrared emitting fabric enhances aerobic energy system and improves exercise tolerance during very heavy intensity, thus confirming the ergogenic effect of this aid.