Determination of the Respiratory Compensation Point by Detecting Changes in Intercostal Muscles Oxygenation by Using Near-Infrared Spectroscopy

Abstract

This study aimed to evaluate if the changes in oxygen saturation levels at intercostal muscles (SmO2-m.intercostales) assessed by near-infrared spectroscopy (NIRS) using a wearable device could determine the respiratory compensation point (RCP) during exercise. Fifteen healthy competitive triathletes (eight males; 29 ± 6 years; height 167.6 ± 25.6 cm; weight 69.2 ± 9.4 kg; V˙O2-máx 58.4 ± 8.1 mL·kg−1·min−1) were evaluated in a cycle ergometer during the maximal oxygen-uptake test (V˙O2-máx), while lung ventilation (V˙E), power output (watts, W) and SmO2-m.intercostales were measured. RCP was determined by visual method (RCPvisual: changes at ventilatory equivalents (V˙E·V˙CO2−1, V˙E·V˙O2−1) and end-tidal respiratory pressure (PetO2, PetCO2) and NIRS method (RCPNIRS: breakpoint of fall in SmO2-m.intercostales). During exercise, SmO2-m.intercostales decreased continuously showing a higher decrease when V˙E increased abruptly. A good agreement between methods used to determine RCP was found (visual vs NIRS) at %V˙O2-máx, V˙O2, V˙E, and W (Bland-Altman test). Correlations were found to each parameters analyzed (r = 0.854; r = 0.865; r = 0.981; and r = 0,968; respectively. p < 0.001 in all variables, Pearson test), with no differences (p < 0.001 in all variables, Student’s t-test) between methods used (RCPvisual and RCPNIRS). We concluded that changes at SmO2-m.intercostales measured by NIRS could adequately determine RCP in triathletes.

Reliability of threshold determination using portable muscle oxygenation monitors during exercise testing: a systematic review and meta-analysis

“…The wearable lactate threshold sensor could be implemented by coaches and athletes Cayot et al 46 N = 9 (M); 5 (F) Recreationally 2 × GXT (separated by 7–10 days) 5-min W-UP (25 W) ↑ 25 W every 180 s * Cycle ergometer LT 2 Moxy VL MOT 2 detection was moderately correlated with the LT 2 and the heart rate. The results do not support the use of two different mathematical methods for MOT 2 determination Contreras-Briceño et al 39 N = 8 (M); 7 (F) Highly trained triathletes GXT 2-min rest 3-min W-UP (100 W) ↑ 20 W every 80 s * Bike on a cycle ergometer VT 2 Moxy 7th IC A good-to-excellent correlation was obtained between MOT 2 and VT 2 for each variable of all analyses in the 7th IC, muscle Driller et al 47 N = 10 (M); 5 (F) Highly Trained Cyclists GXT 3-min 80–120 W ↑ 20 W every 180 s * Bicycle on an ergometer LT 2 BSX Insight GC LT 2 determination through MOT 2 showed an excellent correlation during cycling. These results were shown in all methods for LT 2 detection Farzam et al 48 N = 15 (M); 3 (F) Recreationally GXT 4-min 30 W ↑30 W every 240 s * Cycle ergometer LT 2 Humon Hex, MetaOX* RF MOT 2 determination showed good agreements with LT 2 NIRS portable and NIRS non-portable showed a good correlation during the exercise.…”

“…Our meta-analyses were focused on showing whether the exercise intensity where the first and second thresholds were detected using the portable NIRS was more reliable than the gold standards methods (gas exchange and blood lactate). Table 1 shows how the relationship between MOT and VT was analyzed in 7 studies 16 , 25 , 39 – 43 and in 9 studies for LT 17 , 26 , 41 , 44 – 49 .…”

“…However, the ICC value of two studies were not obtained 46 , 48 . The remaining studies also compared gas exchange with muscle oxygenation in the second threshold in cycling 16 , 39 , 42 , 43 and running 16 , 40 . The results of the different studies suggest that the relationship between both methods in threshold determination is affected by the region assessed by the NIRS device, as good values (ICC = 0.92–0.97) were observed on assessing the intercostalis during cycling 39 .…”

Respiratory muscle training induces additional stress and training load in well-trained triathletes—randomized controlled trial

“…A computation window of 2 s was used. SmO 2 changes during RMT session (ΔSMO 2 B) and SmO 2 recovery after RMT session (ΔSMO 2 A) were recorded to assess exercise intensity ( Contreras-Briceño et al, 2022 ) as below: …”

Agreement between Ventilatory Thresholds and Bilaterally Measured Vastus Lateralis Muscle Oxygen Saturation Breakpoints in Trained Cyclists: Effects of Age and Performance

“…Nevertheless, the general practice for study design has been comparing oxygen uptake data to muscle deoxygenation [ 14 , 15 , 16 ]. Although, commonly available NIRS devices measure oxygen saturation in arbitrary units and therefore it would be more applicable to use the same parameters the data are measured in as has been performed in latter studies [ 11 , 12 , 13 , 17 , 18 ]. As mentioned before, many studies have been performed to establish the correlation between thresholds identified using pulmonary gas exchange devices and NIRS signals.…”