Near infrared spectroscopy-derived interstitial hydrogen ion concentration and tissue oxygen saturation during ambulation

Abstract

The objective of this study was to determine whether walking and running at different treadmill speeds resulted in different metabolic and cardiovascular responses in the vastus lateralis (VL) and lateral gastrocnemius (LG) by examining metabolite accumulation and tissue oxygen saturation. Ten healthy subjects (6 males, 4 females) completed a submaximal treadmill exercise test, beginning at 3.2 km h(-1) and increasing by 1.6 km h(-1) increments every 3 min until reaching 85% of age-predicted maximal heart rate. Muscle tissue oxygenation (SO(2)), total hemoglobin (HbT) and interstitial hydrogen ion concentration ([H(+)]) were calculated from near infrared spectra collected from VL and LG. The [H(+)] threshold for each muscle was determined using a simultaneous bilinear regression. Muscle and treadmill speed effects were analyzed using a linear mixed model analysis. Paired t-tests were used to test for differences between muscles in the [H(+)] threshold. SO(2) decreased (P = 0.001) during running in the VL and LG, but the SO(2) response across treadmill speeds was different between muscles (P = 0.047). In both muscles, HbT and [H(+)] increased as treadmill speed increased (P < 0.001), but the response to exercise was not different between muscles. The [H(+)] threshold occurred at a lower whole-body VO(2) in the LG (1.22 ± 0.63 L min(-1)) than in the VL (1.46 ± 0.58 L min(-1), P = 0.01). In conclusion, interstitial [H(+)] and SO(2) are aggregate measures of local metabolite production and the cardiovascular response. Inferred from simultaneous SO(2) and [H(+)] measures in the VL and LG muscles, muscle perfusion is well matched to VL and LG work during walking, but not running.

Alveolar gas exchange and tissue oxygenation during incremental treadmill exercise, and their associations with blood O2 carrying capacity

“…In the leg muscle (m. vastus lateralis), the oxygenation pattern is in accordance with other studies that have examined incremental treadmill exercise (Hiroyuki et al, 2002; Lee et al, 2011). At the onset of baseline walking, TSI immediately increased above standing level, which indicates increased leg muscle oxygenation.…”

“…Varying running mechanics across subjects may also explain the inter-individual variability of oxygenation responses observed in our subjects, also noted by previous investigators (e.g., Lee et al, 2011), and reflects the variability of metabolic efficiency of running, which may vary as much as 40% across individuals (Joyner and Coyle, 2008). One must also note that we only measured m. vastus lateralis and m. biceps brachii, while there is heterogeneity in activation and metabolism within muscle groups during exercise (Kalliokoski et al, 2011).…”

“…Tissue oxygenation results from arterial O 2 saturation (SpO 2 %), local metabolic rate, and tissue blood flow (Lee et al, 2011). In this study, SpO 2 % remained relatively constant at 95–100% during submaximal intensities, and was 93% on average at peak exercise, which indicates mild-to-moderate exercise-induced arterial hypoxemia (Dempsey and Wagner, 1999).…”

“…During incremental treadmill exercise, oxygenation in m. vastus lateralis remains relatively constant during walking, but decreases during running as a result of increased local O 2 extraction and utilization due to increasing muscle work (Hiroyuki et al, 2002; Lee et al, 2011). Arm muscle oxygenation has not been studied during incremental treadmill exercise, but during incremental cycling, an initial moderate decrease in oxygenation followed by a rapid decrease during more severe exercise has been reported (Ogata et al, 2007; Peltonen et al, 2012).…”

The efficacy of novel anatomical sites for the assessment of muscle oxygenation during central hypovolemia

“…For example, if an individual is in an active state immediately prior to a hemorrhagic insult (such as during combat), or a patient is moving the muscle site where the sensor is placed, increased muscle activity will also affect SmO 2 , 18,19 even in the absence of decreasing central blood volume. Ideally, injury detection algorithms should be developed that can allow differentiation between decreases in SmO 2 that occur with increased muscle activity (e.g., with movement sensors), and those that are characteristic of blood loss.…”