Changes In Muscle Oxygenation Research Articles

Changes in Spinal Muscle Oxygenation and Perfusion During the Biering-Sørensen Test: Preliminary Results of a Study Employing NIRS-Based Muscle Oximetry.

We measured muscle perfusion in healthy subjects during the Biering-Sørensen (BS) test (the gold standard for evaluating back muscle endurance) using a commercial near-infrared spectroscopy (NIRS) device. We analysed data sets of five female healthy subjects (age: 34 ± 15years) who reached the maximum of 4 min during the BS test. Muscle oxygenation (SmO2) and perfusion ([tHb]) were measured using the Moxy NIRS device (Fortiori Design LLC, Hutchinson, USA). Probes were set unilaterally on M. longissimus, M. iliocostalis and M. multifidus. Additionally, mean arterial blood pressure (MAP), pulse pressure (PP), heart rate (HR), arterial oxygen saturation (SpO2) and lactate (pre, task, post) were measured. We observed (i) a large inter-subject variability in the SmO2 and [tHb] responses in the three muscles (i.e., SmO2 desaturations in the in M. longissimus across subjects during the task ranging from 1.1% to -56.6%), and (ii) a consistent response of the systemic signals in all subjects (i.e., increase in MAP, PP and HR). Lactate changes (post task minus task period) correlated with changes in PP and SmO2 of the multifidus muscle. Our preliminary results showed that during the BS test the response in the peripheral muscles was more variable than the central systemic response. A goal for future investigations is to explain this variability in the periphery by considering, for example, subject-specific changes in systemic cardiovascular activity, lactate and in the microvascular perfusion of muscle tissue.

Near Infrared Spectroscopy (NIRS) Observation of Vastus Lateralis (Muscle) and Prefrontal Cortex (Brain) Tissue Oxygenation During Synchronised Swimming Routines in Elite Athletes.

The development of underwater Near-Infrared Spectroscopy (uNIRS) has enabled the measurement of tissue oxygenation within the swim environment. Unique physiological responses, such as the diving reflex, have been shown to occur during synchronized swimming and demonstrate an innate oxygen-conserving reflex. However, the prevalence of a sudden loss of consciousness ('hypoxic blackout') is an ongoing concern in this swim population. The purpose of this study was to investigate the reported low tissue oxygen conditions experienced in elite level synchronized swimmers (SyncS) during swim routines. Changes in peripheral muscle and brain oxygenation (Tissue Saturation Index (TSI %)) were continuously recorded during simulated synchronized swim routines. Six elite female synchronized swimmers were assessed; age 29.0 ± 4.4years; height 168.4 ± 7.1cm; weight 53.2 ± 3.2kg; quadriceps skin fold; 10.2 ± 0.8mm; ΔTSI (%) between the vastus lateralis (VL) and prefrontal cortex (PFC) were analyzed using paired (two-tailed) t-tests. The level of significance for analysis was set at p<0.05. Significant difference (p=0.001) was found in ΔTSI (%) between the VL and PFC. During dynamic leg kicking exercise, the initial effect of each leg kicking sequence is a rapid drop in TSI (%). This is consistent with an initial constriction (drop in blood flow in the muscle) accompanied by an increase in oxygen consumption. Cerebral oxygenation (PFC) remained largely unchanged during both maximal breath-hold and during vigorous exercise, presumably due to protective mechanisms in the brain in this population. We conclude that uNIRS is able to provide novel insights into SyncS hemodynamic responses and could be used to inform on the safety of new routines.

Muscle Oximetry in Sports Science: A Systematic Review.

Since the introduction (in 2006) of commercially available portable wireless muscle oximeters, the use of muscle near-infrared spectroscopy (NIRS) technology is gaining in popularity as an application to observe changes in muscle metabolism and muscle oxygenation during and after exercise or training interventions in both laboratory and applied sports settings. The objectives of this systematic review were to highlight the application of muscle oximetry in evaluating oxidative skeletal muscle performance to sport activities and emphasize how this technology has been applied to exercise and training. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed in a systematic fashion to search, assess and synthesize existing literature on this topic. The Scopus and MEDLINE/PubMed electronic databases were searched to 1 March 2017. Potential inclusions were screened against eligibility criteria relating to recreationally trained to elite athletes, with or without training programs, who must have assessed physiological variables monitored by commercial oximeters or NIRS instrumentation. Of the 14,609 identified records, only 57 studies met the eligibility criteria. This systematic review highlighted a number of key findings in 16 sporting activities. Overall, NIRS information can be used as a marker of skeletal muscle oxidative capacity and for analyzing muscle performance factors. Although NIRS instrumentation is promising in evaluating oxidative skeletal muscle performance when used in sport settings, there is still the need for further instrumental development and randomized/longitudinal trials to support the detailed advantages of muscle oximetry utilization in sports science.

Effect of high-flow nasal therapy during acute aerobic exercise in patients with chronic obstructive pulmonary disease after exacerbation: protocol for a randomised, controlled, cross-over trial

IntroductionEarly pulmonary rehabilitation is recommended after a severe exacerbation of chronic obstructive pulmonary disease (COPD). However, this is difficult to implement, particularly for exercise training. High-flow nasal therapy (HFNT) may...

Dissociation of local and global skeletal muscle oxygen transport metrics in type 2 diabetes

AimsExercise capacity is impaired in type 2 diabetes, and this impairment predicts excess morbidity and mortality. This defect appears to involve excess skeletal muscle deoxygenation, but the underlying mechanisms remain unclear. We hypothesized that reduced blood flow, reduced local recruitment of blood volume/hematocrit, or both contribute to excess skeletal muscle deoxygenation in type 2 diabetes. MethodsIn patients with (n=23) and without (n=18) type 2 diabetes, we recorded maximal reactive hyperemic leg blood flow, peak oxygen utilization during cycling ergometer exercise (VO2peak), and near-infrared spectroscopy-derived measures of exercise-induced changes in skeletal muscle oxygenation and blood volume/hematocrit. ResultsWe observed a significant increase (p<0.05) in skeletal muscle deoxygenation in type 2 diabetes despite similar blood flow and recruitment of local blood volume/hematocrit. Within the control group skeletal muscle deoxygenation, local recruitment of microvascular blood volume/hematocrit, blood flow, and VO2peak are all mutually correlated. None of these correlations were preserved in type 2 diabetes. ConclusionsThese results suggest that in type 2 diabetes 1) skeletal muscle oxygenation is impaired, 2) this impairment may occur independently of bulk blood flow or local recruitment of blood volume/hematocrit, and 3) local and global metrics of oxygen transport are dissociated.

Cardiopulmonary Responses, Brain And Muscle Oxygenation During Incremental Exercise On Acute Hypoxia And Hyperoxia

Changes in inspired oxygen concentration will be affect the peak oxygen uptake compared with normoxia. These underlying mechanism are not fully understood, but peripheral and central mechanisms have been proposed. PURPOSE: Our study focuses on the effect of acute moderate hypoxia and hyperoxia on cardiopulmonary responses, brain and muscle oxygenation during exercise. METHODS: Seven healthy male subjects performed on incremental maximal exercise test under normoxia (Norm: 20.9 FIO2), hypoxia (Hypo: 14.5% FIO2) and hyperoxia (Hyper: 28.5% FIO2) conditions. We measured cardiopulmonary measurements (VE, VO2, HR and Q) and blood gas (PO2 and PCO2) on incremental exercise. Near-infrared spectroscopy (NIRS) was also used to monitor concentration (μM) changes of oxy- and deoxyhemoglobin ([INCREMENT][O2Hb], [INCREMENT][HHb]) in left frontal cortex region of the forehead and ipsilateral vastus lateralis muscle. Changes in total Hb and StO2 were calculated and used as index of change in regional blood volume. Repeated-measures ANOVA were performed across treatments. RESULTS: VO2 peak decreased in Hypo (38.5±3.1 ml/kg/min, p<0.05) and no difference in Hyper (42.6±3.4 ml/kg/min) compered with Norm (42.2±3.9 ml/kg/min). But blood PO2 at rest and moderate exercise was low in Hypo (57.7±3.1 and 52.2±5.4 mmHg, p<0.05) and high in Hyper (98.6±8.8 and 105.3±9.3 mmHg, p<0.05) compared with Norm (79.3±12.6 and 84.3±4.7 mmHg). Muscle oxygenation dropped progressively during Hypo, and also changes in muscle oxygenation during Hyper were similar to Norm. Interestingly, Brain oxygenation ([INCREMENT][O2Hb]) was slightly increased and deoxygenation ([INCREMENT][HHb]) was increased during exercise under each three conditions, respectively. Furthermore, changes brain and muscle oxygenation was also greater in Hypo compared with Norm and Hyper (p>0.05). CONCLUSIONS: Acute hypoxia decrease oxygen uptake with decreased muscle oxygenation and slightly increased brain oxygenation. But it is unlikely that changes in brain and muscle oxygenation was related with oxygen uptake in hyperoxia, despite a similar difference absolute PO2 in inspired oxygen and blood from hypoxia and/or hyperoxia to normoxia.

Hemodynamic function during finger force production tasks in healthy adults.

Near-infrared spectroscopy (NIRS) is a noninvasive technique used to measure muscle hemodynamics. The focus of this study was to evaluate changes in muscle oxygenation during sustained maximal force production in young, healthy control individuals to establish baseline function in an ideal population. NIRS was used to monitor reduced hemoglobin (HbR) and oxygenated hemoglobin (HbO) in forearm muscles. Hemodynamic responses during force production tasks were monitored in real time. During handgrip exercises, maximal force production declined significantly. Increased HbR was found while HbO remained constant. The correlation between force production and HbO was positive (r = 0.18), while the correlation between force and HbR was negative (r = -0.48). The application of NIRS to monitor the correlation between force production and hemodynamic measures in the forearm was successful. These data set the foundation for future use of NIRS as a diagnostic tool for individuals with peripheral vascular disease: Muscle Nerve 56: 472-478, 2017.

Limitations of skeletal muscle oxygen delivery and utilization during moderate-intensity exercise in moderately impaired patients with chronic heart failure.

The extent and speed of transient skeletal muscle deoxygenation during exercise onset in patients with chronic heart failure (CHF) are related to impairments of local O2 delivery and utilization. This study examined the physiological background of submaximal exercise performance in 19 moderately impaired patients with CHF (Weber class A, B, and C) compared with 19 matched healthy control (HC) subjects by measuring skeletal muscle oxygenation (SmO2) changes during cycling exercise. All subjects performed two subsequent moderate-intensity 6-min exercise tests (bouts 1 and 2) with measurements of pulmonary oxygen uptake kinetics and SmO2 using near-infrared spatially resolved spectroscopy at the vastus lateralis for determination of absolute oxygenation values, amplitudes, kinetics (mean response time for onset), and deoxygenation overshoot characteristics. In CHF, deoxygenation kinetics were slower compared with HC (21.3 ± 5.3 s vs. 16.7 ± 4.4 s, P < 0.05, respectively). After priming exercise (i.e., during bout 2), deoxygenation kinetics were accelerated in CHF to values no longer different from HC (16.9 ± 4.6 s vs. 15.4 ± 4.2 s, P = 0.35). However, priming did not speed deoxygenation kinetics in CHF subjects with a deoxygenation overshoot, whereas it did reduce the incidence of the overshoot in this specific group (P < 0.05). These results provide evidence for heterogeneity with respect to limitations of O2 delivery and utilization during moderate-intensity exercise in patients with CHF, with slowed deoxygenation kinetics indicating a predominant O2 utilization impairment and the presence of a deoxygenation overshoot, with a reduction after priming in a subgroup, indicating an initial O2 delivery to utilization mismatch.

Mitochondrial function assessed by 31P MRS and BOLD MRI in non-obese type 2 diabetic rats.

The study aims to characterize age‐associated changes in skeletal muscle bioenergetics by evaluating the response to ischemia‐reperfusion in the skeletal muscle of the Goto‐Kakizaki (GK) rats, a rat model of non‐obese type 2 diabetes (T2D). 31P magnetic resonance spectroscopy (MRS) and blood oxygen level‐dependent (BOLD) MRI was performed on the hindlimb of young (12 weeks) and adult (20 weeks) GK and Wistar (control) rats. 31P‐MRS and BOLD‐MRI data were acquired continuously during an ischemia and reperfusion protocol to quantify changes in phosphate metabolites and muscle oxygenation. The time constant of phosphocreatine recovery, an index of mitochondrial oxidative capacity, was not statistically different between GK rats (60.8 ± 13.9 sec in young group, 83.7 ± 13.0 sec in adult group) and their age‐matched controls (62.4 ± 11.6 sec in young group, 77.5 ± 7.1 sec in adult group). During ischemia, baseline‐normalized BOLD‐MRI signal was significantly lower in GK rats than in their age‐matched controls. These results suggest that insulin resistance leads to alterations in tissue metabolism without impaired mitochondrial oxidative capacity in GK rats.

Cerebral and Muscle Oxygenation During Intermittent Hypoxia Exposure in Healthy Humans.

To evaluate changes in muscle and cerebral oxygenation during intermittent hypoxia (IH). Fifteen healthy subjects were exposed to 45-min IH (2-min cycles). Arterial blood oxygen saturation (SpO2), prefrontal cortex and brachial biceps muscle oxygenation (assessed by near-infrared spectroscopy), heart rate, and ventilation were continuously recorded. During 2-min IH cycles, changes in SpO2 (9.2% ± 3.3%) were associated with significant changes in cortex oxygenation (3.2% ± 1.8%), minute ventilation, and heart rate, but no change in muscle oxygenation (0.2% ± 1.0%). Fluctuations of blood oxygen levels comparable to severe obstructive sleep apnea translate into distinct pattern of oxygenation changes in the muscle and cortex.

Effects of Acute Hypoxia and Hyperoxia on Oxygen Uptake, Brain and Muscle Oxygenation during Incremental Exercise

Changes in inspired oxygen concentration will be affect the peak oxygen uptake compared with normoxia. These underlying mechanism are not fully understood, but central and peripheral mechanisms have been proposed. PURPOSE: Our study focuses on the effect of acute hypoxia and hyperoxia on oxygen uptake, brain and muscle oxygenation during exercise. METHODS: Eight healthy male subjects performed on incremental maximal exercise test (15W/min step) under normoxia (Norm: 20.9 FIO2), acute hypoxia (Hypox: 14.5% FIO2) and acute hyperoxia (Hyper: 28.0% FIO2) conditions. The order of each condition was randomized and trials were spaced by 5 days. We measured oxygen uptake (VO2 peak) on incremental exercise. Near-infrared spectroscopy (NIRS) was used to monitor concentration (μM) changes of oxy- and deoxyhemoglobin ([INCREMENT][O2Hb], [INCREMENT][HHb]) in left frontal cortex region of the forehead and ipsilateral vastus lateralis muscle. Changes in total Hb and StO2 were calculated ([INCREMENT][THb] = [INCREMENT][O2Hb] + [INCREMENT][HHb], [INCREMENT][StO2]) and used as index of change in regional blood volume. Repeated-measures ANOVA were performed across treatments. RESULTS: VO2 peak decreased in Hypox (38.6±4.0ml/kg/min, p>0.05) and slightly increased in Hyper (45.2±7.5ml/kg/min) compered with Norm (43.3±5.9ml/kg/min). Muscle oxygenation dropped progressively during Hypox (decrease [INCREMENT][O2Hb]; −1.79±0.61μM and [INCREMENT]StO2; −19.55±3.86%, increase [INCREMENT][HHb]; 3.37±0.96μM at 100% Powerpeak), and also changes in muscle oxygenation during Hyper (decrease [INCREMENT][O2Hb]; −1.26±0.76μM and [INCREMENT]StO2; −16.30±5.13%, increase [INCREMENT][HHb]; 2.96±1.06μM at 100% Powerpeak) were similar to Norm (decrease [INCREMENT][O2Hb]; −1.35±0.76μM and [INCREMENT]StO2; −16.17±5.30%, increase [INCREMENT][HHb]; 3.01±1.35μM at 100% Powerpeak). Interestingly, Brain oxygenation ([INCREMENT][O2Hb]) was slightly increased and deoxygenation ([INCREMENT][HHb]) was increased during exercise under each three conditions, respectively. Furthermore, changes brain and muscle oxygenation was also greater in Hypox compared with Norm and Hyper (p>0.05). CONCLUSIONS: Acute hypoxia decrease oxygen uptake with decreased muscle oxygenation and slightly increased brain oxygenation. But it is unlikely that changes in brain and muscle oxygenation was relate with oxygen uptake in hyperoxia, despite a similar change absolute PO2 from hypoxia and/or hyperoxia to normoxia.

Relationship of post-exercise muscle oxygenation and duration of cycling exercise.

BackgroundAerobic adaptations following interval training are supposed to be mediated by increased local blood supply. However, knowledge is scarce on the detailed relationship between exercise duration and local post-exercise blood supply and oxygen availability. This study aimed to examine the effect of five different exercise durations, ranging from 30 to 240 s, on post-exercise muscle oxygenation and relative changes in hemoglobin concentration.MethodsHealthy male subjects (N = 18) performed an experimental protocol of five exercise bouts (30, 60, 90, 120, and 240 s) at 80 % of peak oxygen uptake left({overset{.}{mathrm{V}}mathrm{O}}_{2mathrm{peak}}right) in a randomized order, separated by 5-min recovery periods. To examine the influence of aerobic fitness, we compared subjects with gas exchange thresholds (GET) above 60 % overset{.}{mathrm{V}}{mathrm{O}}_{2mathrm{peak}} (GET60+) with subjects reaching GET below 60 % overset{.}{mathrm{V}}{mathrm{O}}_{2mathrm{peak}} (GET60−). overset{.}{mathrm{V}}{mathrm{O}}_2 and relative changes in concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, and total hemoglobin were continuously measured with near-infrared spectroscopy of the vastus lateralis muscle.ResultsPost-exercise oxygen availability and local blood supply increased significantly until the 90-s exercise duration and reached a plateau thereafter. Considering aerobic fitness, the GET60+ group reached maximum post-exercise oxygen availability earlier (60 s) than the GET60− group (90 s).ConclusionsOur results suggest that (1) 90 s has evolved as the minimum interval duration to enhance local oxygen availability and blood supply following cycling exercise at 80 % overset{.}{mathrm{V}}{mathrm{O}}_{2mathrm{peak}} ; whereas (2) 60 s is sufficient to trigger the same effects in subjects with GET60 + .

Effects of friction massage of the popliteal fossa on dynamic changes in muscle oxygenation and ankle flexibility.

[Purpose] This study aimed to examine whether or not friction massage of the popliteal fossa would be effective for achieving dynamic changes in muscle oxygenation and ankle flexibility. [Subjects and Methods] Twelve healthy male university students participated. Before and after friction massage, dynamic changes in muscle oxygenation and ankle flexibility were measured by near-infrared spectroscopy to evaluate its efficacy. [Results] Oxygenated hemoglobin was significantly higher after as compared to before massage. The range of ankle dorsiflexion tended to increase after massage. [Conclusion] These results suggest that friction massage of the popliteal fossa stimulates venous return in the lower leg.

Underwater Near-Infrared Spectroscopy: Muscle Oxygen Changes in the Upper and Lower Extremities in Club Level Swimmers and Triathletes.

To date, measurements of oxygen status during swim exercise have focused upon systemic aerobic capacity. The development of a portable, waterproof NIRS device makes possible a local measurement of muscle hemodynamics and oxygenation that could provide a novel insight into the physiological changes that occur during swim exercise. The purpose of this study was to observe changes in muscle oxygenation in the vastus lateralis (VL) and latissimus dorsi (LD) of club level swimmers and triathletes. Ten subjects, five club level swimmers and five club level triathletes (three men and seven women) were used for assessment. Swim group; mean±SD=age 21.2±1.6 years; height 170.6±7.5 cm; weight 62.8±6.9 kg; vastus lateralis skin fold 13.8±5.6 mm; latissimus dorsi skin fold 12.6±3.7. Triathlete group; mean±SD=age 44.0±10.5 years; height 171.6±7.0 cm; weight 68.6±12.7 kg; vastus lateralis skin fold 11.8±3.5 mm; latissimus dorsi skin fold 11.2±3.1. All subjects completed a maximal 200 m freestyle swim, with the PortaMon, a portable NIR device, attached to the subject's dominant side musculature. ΔTSI% between the vastus lateralis and latissimus dorsi were analysed using either paired (2-tailed) t-tests or Wilcoxon signed rank test. The level of significance for analysis was set at p<0.05. No significant difference (p=0.686) was found in ΔTSI (%) between the VL and LD in club level swimmers. A significant difference (p=0.043) was found in ΔTSI (%) between the VL and LD in club level triathletes. Club level swimmers completed the 200 m freestyle swim significantly faster (p=0.04) than club level triathletes. Club level swimmers use both the upper and lower muscles to a similar extent during a maximal 200 m swim. Club level triathletes predominately use the upper body for propulsion during the same exercise. The data produced by NIRS in this study are the first of their kind and provide insight into muscle oxygenation changes during swim exercise which can indicate the contribution of one muscle compared to another. This also enables a greater understanding of the differences in swimming techniques seen between different cohorts of swimmers and potentially within individual swimmers.

Muscle Oxygenation During Running Assessed by Broad Band NIRS.

We used spatially resolved near-infrared spectroscopy (SRS-NIRS) to assess calf and thigh muscle oxygenation during running on a motor-driven treadmill. Two protocols were used: An incremental speed protocol was performed in 5-min stages, while a pacing paradigm modulated the step frequency (2.3Hz [SLow]; 3.3Hz [SHigh]) during a constant velocity for 2min each. A SRS-NIRS broadband system was used to measure total haemoglobin concentration and oxygen saturation (SO2). An accelerometer was placed on the hip joints to measure limb acceleration through the experiment. The data showed that the calf desaturated to a significantly lower level than the thigh. During the pacing protocol, SO2 was significantly different between the high and low step frequencies. Additionally, physiological data as measured by spirometry were different between the SLow vs. SHigh pacing trials. Significant differences in VO2 at the same workload (speed) indicate alterations in mechanical efficiency. These data suggest that SRS broadband NIRS can be used to discern small changes in muscle oxygenation, making this device useful for metabolic exercise studies in addition to spirometry and movement monitoring by accelerometers.

Effects of Cold Water Immersion on Muscle Oxygenation During Repeated Bouts of Fatiguing Exercise: A Randomized Controlled Study.

Postexercise cold water immersion has been advocated to athletes as a means of accelerating recovery and improving performance. Given the effects of cold water immersion on blood flow, evaluating in vivo changes in tissue oxygenation during cold water immersion may help further our understanding of this recovery modality. This study aimed to investigate the effects of cold water immersion on muscle oxygenation and performance during repeated bouts of fatiguing exercise in a group of healthy young adults.Twenty healthy subjects performed 2 fatiguing bouts of maximal dynamic knee extension and flexion contractions both concentrically on an isokinetic dynamometer with a 10-min recovery period in between. Subjects were randomly assigned to either a cold water immersion (treatment) or passive recovery (control) group. Changes in muscle oxygenation were monitored continuously using near-infrared spectroscopy. Muscle performance was measured with isokinetic dynamometry during each fatiguing bout. Skin temperature, heart rate, blood pressure, and muscle soreness ratings were also assessed. Repeated measures ANOVA analysis was used to evaluate treatment effects.The treatment group had a significantly lower mean heart rate and lower skin temperature compared to the control group (P < 0.05). Cold water immersion attenuated a reduction in tissue oxygenation in the second fatiguing bout by 4% when compared with control. Muscle soreness was rated lower 1 day post-testing (P < 0.05). However, cold water immersion had no significant effect on muscle performance in subsequent exercise.As the results show that cold water immersion attenuated decreased tissue oxygenation in subsequent exercise performance, the metabolic response to exercise after cold water immersion is worthy of further exploration.

The Effects of Passive Cycling Exercise for 20 min on Cardiorespiratory Dynamics in Healthy Men [corrected

An increase in the incidence rate of cardiovascular disease is attributed to high daily sitting time, while a drop in risk of cardiovascular disease comes from a decrease in daily sitting time, rather than an increase in physical activity levels. Although short-duration passive exercise increases energy expenditure and blood flow, few studies have reported on the responses of cardiorespiratory dynamics to long-duration passive exercise. The purpose of this study was to consider the effect of long-duration passive exercise for 20 min on cardiorespiratory and muscle oxygen dynamics. Eight healthy men continuously performed passive exercise using a cycle ergometer for 20 min at 50 rpm. Changes in oxygen uptake, cardiac output and muscle oxygenation were measured during passive cycling exercise. The oxygen uptake at 1 min after the start of passive exercise was significantly increased, compared to resting level, but subsequently returned to the same as resting level. Cardiac output showed no change during passive cycling exercise. Tissue oxygen saturation increased after the start of passive exercise and subsequently maintained steady state. These results suggest that the effect of increases in energy expenditure was not maintained by passive exercise for 20 min. In addition, it is likely that passive cycling exercise for 20 min has an effect on peripheral circulation, although the exercise seems to have no effect on central circulation.

Development of Portable, Wireless and Smartphone Controllable Near-Infrared Spectroscopy System.

We have developed portable near-infrared tissue oxygenation monitoring systems, called the "PocketNIRS Duo" and the "PocketNIRS HM", which features wireless data communication and a sampling rate of up to 60 data readings per second. The systems can be controlled by smartphone or personal computer. We demonstrate the efficacy of the systems for monitoring changes in brain and arm muscle hemodynamics and oxygenation in breath-holding and cuff-occlusion tests, respectively.Our systems should prove to be useful as an oxygenation monitor not only in research but also in healthcare applications.

Influence of Hypoxic Interval Training and Hyperoxic Recovery on Muscle Activation and Oxygenation in Connection with Double-Poling Exercise.

Here, we evaluated the influence of breathing oxygen at different partial pressures during recovery from exercise on performance at sea-level and a simulated altitude of 1800 m, as reflected in activation of different upper body muscles, and oxygenation of the m. triceps brachii. Ten well-trained, male endurance athletes (25.3±4.1 yrs; 179.2±4.5 cm; 74.2±3.4 kg) performed four test trials, each involving three 3-min sessions on a double-poling ergometer with 3-min intervals of recovery. One trial was conducted entirely under normoxic (No) and another under hypoxic conditions (Ho; FiO2 = 0.165). In the third and fourth trials, the exercise was performed in normoxia and hypoxia, respectively, with hyperoxic recovery (HOX; FiO2 = 1.00) in both cases. Arterial hemoglobin saturation was higher under the two HOX conditions than without HOX (p<0.05). Integrated muscle electrical activity was not influenced by the oxygen content (best d = 0.51). Furthermore, the only difference in tissue saturation index measured via near-infrared spectroscopy observed was between the recovery periods during the NoNo and HoHOX interventions (P<0.05, d = 0.93). In the case of HoHo the athletes’ Pmean declined from the first to the third interval (P < 0.05), whereas Pmean was unaltered under the HoHOX, NoHOX and NoNo conditions. We conclude that the less pronounced decline in Pmean during 3 x 3-min double-poling sprints in normoxia and hypoxia with hyperoxic recovery is not related to changes in muscle activity or oxygenation. Moreover, we conclude that hyperoxia (FiO2 = 1.00) used in conjunction with hypoxic or normoxic work intervals may serve as an effective aid when inhaled during the subsequent recovery intervals.

Muscle oxygen changes following Sprint Interval Cycling training in elite field hockey players.

This study examined the effects of Sprint Interval Cycling (SIT) on muscle oxygenation kinetics and performance during the 30-15 intermittent fitness test (IFT). Twenty-five women hockey players of Olympic standard were randomly selected into an experimental group (EXP) and a control group (CON). The EXP group performed six additional SIT sessions over six weeks in addition to their normal training program. To explore the potential training-induced change, EXP subjects additionally completed 5 x 30s maximal intensity cycle testing before and after training. During these tests near-infrared spectroscopy (NIRS) measured parameters; oxyhaemoglobin + oxymyoglobin (HbO2+ MbO2), tissue deoxyhaemoglobin + deoxymyoglobin (HHb+HMb), total tissue haemoglobin (tHb) and tissue oxygenation (TSI %) were taken. In the EXP group (5.34±0.14 to 5.50±0.14m.s-1) but not the CON group (pre = 5.37±0.27 to 5.39±0.30m.s-1) significant changes were seen in the 30-15IFT performance. EXP group also displayed significant post-training increases during the sprint cycling: ΔTSI (−7.59±0.91 to −12.16±2.70%); ΔHHb+HMb (35.68±6.67 to 69.44±26.48μM.cm); and ΔHbO2+ MbO2 (−74.29±13.82 to −109.36±22.61μM.cm). No significant differences were seen in ΔtHb (−45.81±15.23 to −42.93±16.24). NIRS is able to detect positive peripheral muscle oxygenation changes when used during a SIT protocol which has been shown to be an effective training modality within elite athletes.