Effect of high-intensity interval training on the profile of muscle deoxygenation heterogeneity during incremental exercise

Comparing the effects of dynamic and holding isometric contractions on cardiovascular, perceptual, and near-infrared spectroscopy parameters: A pilot study

The aim of this pilot study was to assess the effect of muscle contraction type on SmO2 during a dynamic contraction protocol (DYN) and a holding isometric contraction protocol (ISO) in the back squat exercise. Ten voluntary participants (age: 26.6 ± 5.0 years, height: 176.8 ± 8.0 cm, body mass: 76.7 ± 8.1 kg, and one-repetition maximum (1RM): 112.0 ± 33.1 kg) with back squat experience were recruited. The DYN consisted of 3 sets of 16 repetitions at 50% of 1RM (56.0 ± 17.4 kg), with a 120-second rest interval between sets and 2 seconds per movement cycle. The ISO consisted of 3 sets of 1 isometric contraction with the same weight and duration as the DYN (32 seconds). Through near-infrared spectroscopy (NIRS) in the vastus lateralis (VL), soleus (SL), longissimus (LG), and semitendinosus (ST) muscles, the minimum SmO2 (SmO2 min), mean SmO2 (SmO2 avg), percent change from baseline (SmO2 Δdeoxy) and time to recovery 50% of baseline value (t SmO2 50%reoxy) were determined. No changes in SmO2 avg were found in the VL, LG, and ST muscles, however the SL muscle had lower values in DYN, in the 1st set (p = 0.002) and in the 2nd set (p = 0.044). In terms of SmO2 min and ΔSmO2 deoxy, only the SL muscle showed differences (p≤0.05) and lower values in the DYN compared to ISO regardless of the set. The t SmO2 50%reoxy was higher in the VL muscle after ISO, only in the 3rd set. These preliminary data suggested that varying the type of muscle contraction in back squat with the same load and exercise time resulted in a lower SmO2 min in the SL muscle in DYN, most likely because of a higher demand for specialized muscle activation, indicating a larger oxygen supply-consumption gap.

Repeated sprint training under hypoxia improves aerobic performance and repeated sprint ability by enhancing muscle deoxygenation and markers of angiogenesis in rugby sevens

OBJECTIVE

To evaluate the effects of repeated sprint (RS) training in hypoxia on aerobic performance, repeated sprint ability (RSA), and muscle oxygenation in Rugby Sevens.

METHODS

Fourteen Rugby Sevens players were randomly allocated into hypoxic (RSH, F_IO₂ = 14.5%, n = 7) or normoxic (RSN, F_IO₂ = 20.9%, n = 7) groups. Both groups underwent RS training consisting of 3 sets of 6-s × 10 sprints at 140% of velocity at peak oxygen uptake ([Formula: see text]) on a motorized treadmill, 3 days/week for 6 weeks in addition to usual training. Hematological variables, hypoxia-inducible factor-1 alpha (HIF-1α), and vascular endothelial growth factor (VEGF) concentrations were measured. Aerobic performance, RSA, and muscle oxygenation during the running-based anaerobic sprint (RAS) test were analyzed.

RESULTS

RSH caused no changes in hemoglobin concentration and hematocrit but significant improvements in [Formula: see text] (7.5%, p = 0.03, ES = 1.07), time to exhaustion (17.6%, p = 0.05, ES = 0.92), and fatigue index (FI, - 12.3%, p = 0.01, ES = 1.39) during the RSA test compared to baseline but not RSN. While ∆deoxygenated hemoglobin was significantly increased both after RSH and RSN (p < 0.05), ∆tissue saturation index (- 56.1%, p = 0.01, ES = 1.35) and ∆oxygenated hemoglobin (- 54.7%, p = 0.04, ES = 0.97) were significantly decreased after RSH. These changes were concomitant with increased levels of HIF-1α and VEGF in serum after RSH with a strong negative correlation between ∆FI and ∆deoxygenated hemoglobin after RSH (r = - 0.81, p = 0.03).

CONCLUSION

There was minimal benefit from adding RSH to standard Rugby Sevens training, in eliciting improvements in aerobic performance and resistance to fatigue, possibly by enhanced muscle deoxygenation and increased serum HIF-1α and VEGF concentrations.

Effects of arm cranking exercise on muscle oxygenation between active and inactive muscles in people with spinal cord injury

Objective: We investigated the effects of the incremental arm-cranking exercise (ACE) on tissue oxygen saturation (StO₂) between active and inactive muscles, and the relationship between peak oxygen uptake (VO_2peak) and changes in the StO₂ in inactive muscles.Design: Observational study.Setting: Community-based supervised intervention.Participants: The participants were individuals with motor and sensory complete spinal cord injury (complete SCI; n = 8) and motor complete but sensory incomplete SCI (incomplete SCI; n = 8), and able-bodied (AB) individuals (n = 8) matched for age, height, and body mass index.Intervention: The ACE was performed at a rate increasing by 10 watts min^-1 until exhaustion.Outcome Measures: VO_2peak, heart rate (HR), and StO₂.Results: While VO_2peak was similar among the groups, peak HR was significantly higher in both SCI groups than in the AB (P < 0.05). In active muscles (biceps brachii), no differences in the StO₂ were observed among the groups (P > 0.05). In inactive muscles (vastus lateralis), the StO₂ in the AB and the incomplete SCI began to decrease at approximately 40% of the peak work rate; however, they remained unchanged in the complete SCI. The reductions in StO₂ in the AB were significantly greater than in the incomplete SCI.Conclusions: These results suggest that sympathetic vasoconstriction occurred in the incomplete SCI and AB, although it did not occur in the complete SCI, probably due to a reduction in sympathetic nerve activity. Sympathetic vasoconstriction in inactive muscles may not contribute to an individual's VO_2peak regardless of their group.

Aerobic Interval Training Impacts Muscle and Brain Oxygenation Responses to Incremental Exercise

The purpose of the present study was to assess the effects of aerobic interval training on muscle and brain oxygenation to incremental ramp exercise. Eleven physically active subjects performed a 6-week interval training period, proceeded and followed by an incremental ramp exercise to exhaustion (25 W min^–1). Throughout the tests pulmonary gas exchange and muscle (Vastus Lateralis) and brain (prefrontal cortex) oxygenation [concentration of deoxygenated and oxygenated hemoglobin, HHb and O₂Hb, and tissue oxygenation index (TOI)] were continuously recorded. Following the training intervention V.⁢O2_peak had increased with 7.8 ± 5.0% (P < 0.001). The slope of the decrease in muscle TOI had decreased (P = 0.017) 16.6 ± 6.4% and the amplitude of muscle HHb and totHb had increased (P < 0.001) 40.4 ± 15.8 and 125.3 ± 43.1%, respectively. The amplitude of brain O₂Hb and totHb had increased (P < 0.05) 40.1 ± 18.7 and 26.8 ± 13.6%, respectively. The training intervention shifted breakpoints in muscle HHb, totHb and TOI, and brain O₂Hb, HHb, totHb and TOI to a higher absolute work rate and V.⁢O2 (P < 0.05). The relative (in %) change in V.⁢O2_peak was significantly correlated to relative (in %) change slope of muscle TOI (r = 0.69, P = 0.011) and amplitude of muscle HHb (r = 0.72, P = 0.003) and totHb (r = 0.52, P = 0.021), but not to changes in brain oxygenation. These results indicate that interval training affects both muscle and brain oxygenation, coinciding with an increase in aerobic fitness (i.e., V.⁢O2_peak). The relation between the change in V.⁢O2_peak and muscle but not brain oxygenation suggests that brain oxygenation per se is not a primary factor limiting exercise tolerance during incremental exercise.

Prevalence and predictors of dropout from high-intensity interval training in sedentary individuals: A meta-analysis

Recent evidence suggests that high-intensity interval training (HIIT) is an effective method to improve fitness and various health markers. However, the tolerability and acceptability of HIIT among sedentary individuals is currently controversially discussed. Therefore, our objective was to investigate the prevalence and predictors of dropout among sedentary individuals in HIIT-based exercise interventions. MEDLINE/PubMed, SPORTDiscus, and Web of Science were searched systematically for relevant articles until 06/2018. Studies included were required to (a) be written in English, (b) include sedentary healthy adults, (c) use some form of HIIT without any complementary intervention, (d) last ≥4 weeks, (e) report detailed description of the applied HIIT protocol, and (f) report data that allow calculation of a dropout rate. Fifty-five studies reporting results from 67 HIIT interventions with 1318 participants met the eligibility criteria. The trim and fill adjusted pooled dropout rate across all interventions was 17.6% (95% confidence interval 14.2-21.5%). Dropout rates were significantly lower in cycling-based interventions compared with studies using running/walking as exercise modality (P < 0.001). Longer session time (β = 0.02, P < 0.05), higher time effort/week (β = 0.005, P < 0.05), and overall time effort/intervention (β = 0.0003, P < 0.05) predicted greater dropout. Exercise intensity was not related to dropout. Our data suggest that HIIT-based interventions are tolerable and acceptable for previously sedentary individuals, exhibiting generally lower dropout rates than commonly reported for traditional exercise programs. Given the association between HIIT volume and dropouts, future studies should further focus on identifying the minimally effective dose of practical HIIT for improving health status. Such efforts would be important to increase implementation and public health impact of HIIT.

The effect of running versus cycling high-intensity intermittent exercise on local tissue oxygenation and perceived enjoyment in 18-30-year-old sedentary men

BACKGROUND

High-intensity interval training (HIIT) has been proposed as a time-efficient exercise format to improve exercise adherence, thereby targeting the chronic disease burden associated with sedentary behaviour. Exercise mode (cycling, running), if self-selected, will likely affect the physiological and enjoyment responses to HIIT in sedentary individuals. Differences in physiological and enjoyment responses, associated with the mode of exercise, could potentially influence the uptake and continued adherence to HIIT. It was hypothesised that in young sedentary men, local and systemic oxygen utilisation and enjoyment would be higher during a session of running HIIT, compared to a session of cycling HIIT.

METHODS

A total of 12 sedentary men (mean ± SD; age 24 ± 3 years) completed three exercise sessions: a maximal incremental exercise test on a treadmill (MAX) followed by two experiment conditions, (1) free-paced cycling HIIT on a bicycle ergometer (HIITCYC) and (2) constant-paced running HIIT on a treadmill ergometer (HIITRUN). Deoxygenated haemoglobin (HHb) in the gastrocnemius (GN), the left vastus lateralis (LVL) and the right vastus lateralis (RVL) muscles, oxygen consumption (VO2), heart rate (HR), ratings of perceived exertion (RPE) and physical activity enjoyment (PACES) were measured during HIITCYC and HIITRUN.

RESULTS

There was a higher HHb in the LVL (p = 0.001) and RVL (p = 0.002) sites and a higher VO2 (p = 0.017) and HR (p < 0.001) during HIITCYC, compared to HIITRUN. RPE was higher (p < 0.001) and PACES lower (p = 0.032) during HIITCYC compared to HIITRUN.

DISCUSSION

In sedentary individuals, free-paced cycling HIIT produces higher levels of physiological stress when compared to constant-paced running HIIT. Participants perceived running HIIT to be more enjoyable than cycling HIIT. These findings have implications for selection of mode of HIIT for physical stress, exercise enjoyment and compliance.

Underwater near-infrared spectroscopy can measure training adaptations in adolescent swimmers

The development of an underwater near-infrared spectroscopy (uNIRS) device has enabled previously unattainable measurements of peripheral muscle hemodynamics and oxygenation to be taken within the natural aquatic environment. The purposes of this study were (i) to trial the use of uNIRS, in a real world training study, and (ii) to monitor the effects of a swim training program upon muscle oxygenation status in short distance swimming. A total of 14 junior club level swimmers completed a repeated swim sprint test before and after an eight week endurance training program. A waterproof, portable Near-Infrared Spectroscopy device was attached to the vastus lateralis. uNIRS successfully measured changes in muscle oxygenation and blood volume in all individuals; rapid sub-second time resolution of the device was able to demonstrate muscle oxygenation changes during the characteristic swim movements. Post training heart rate recovery and swim performance time were significantly improved. uNIRS data also showed significant changes. A larger rise in deoxyhemoglobin during individual sprints suggested training induced an increase in muscle oxygen extraction; a faster recovery time for muscle oxygenation suggested positive training induced changes and significant changes in muscle blood flow also occur. As a strong correlation was seen between an increased reoxygenation rate and an improved swim performance time, these findings support the use of uNIRS as a new performance analysis tool in swimming.

Moderate-intensity endurance training improves endothelial glycocalyx layer integrity in healthy young men

NEW FINDINGS

What is the central question of this study? The main aim of the present study was to determine the effect of prolonged moderate-intensity endurance training on the endothelial glycocalyx layer integrity in relationship to the training-induced changes in oxidative stress and antioxidant defence in humans. What is the main finding and its importance? We have shown, for the first time, a protective effect of prolonged moderate-intensity endurance training on endothelial glycocalyx layer integrity, as judged by significantly lower basal and end-exercise serum concentrations of glycocalyx damage markers, i.e. syndecan-1 and heparan sulfate, accompanied by attenuation of oxidative stress and enhancement of antioxidant defence after training in previously untrained healthy young men. In this study, we evaluated the effect of 20 weeks of moderate-intensity endurance training (ET) on the endothelial glycocalyx layer integrity in relationship to the training-induced changes in antioxidant defence. Eleven healthy young, untrained men performed an incremental cycling exercise bout until exhaustion before and after 20 weeks of ET. Endurance training consisted of 40 min sessions, mainly of moderate intensity (∼50% of maximal oxygen uptake), performed four times per week. Venous blood samples were taken at rest and at the end of the maximal exercise test. Muscle biopsies from vastus lateralis were taken before and after the training. Endurance training resulted in a significant increase in physical capacity (P < 0.05) as reflected by an increase in power output reached at the lactate threshold and at maximal oxygen uptake. Training led to a decrease (P < 0.05) in basal and end-exercise concentrations of blood markers of glycocalyx damage (syndecan-1 and heparan sulfate). The lowering of glycocalyx shedding after the ET was accompanied by an attenuation of oxidative stress, as evidenced by a decrease in the basal plasma concentration of isoprostanes, and by an increase in antioxidant defence, reflected by an enhancement in superoxide dismutase 2 protein content in vastus lateralis (P < 0.05). In contrast, training did not induce a significant increase in basal nitrite/nitrate plasma concentration (P > 0.05). Moderate-intensity ET exerts a pronounced protective effect on endothelial glycocalyx integrity at rest and during exercise, probably through an improvement of antioxidant defence that may represent the vasoprotective mechanisms highly responsive to moderate-intensity endurance training.

The Effect of Active versus Passive Recovery Periods during High Intensity Intermittent Exercise on Local Tissue Oxygenation in 18 - 30 Year Old Sedentary Men

PURPOSE

High intensity interval training (HIIT) has been proposed as a time-efficient format of exercise to reduce the chronic disease burden associated with sedentary behaviour. Changes in oxygen utilisation at the local tissue level during an acute session of HIIT could be the primary stimulus for the health benefits associated with this format of exercise. The recovery periods of HIIT effect the physiological responses that occur during the session. It was hypothesised that in sedentary individuals, local and systemic oxygen utilisation would be higher during HIIT interspersed with active recovery periods, when compared to passive recovery periods.

METHODS

Twelve sedentary males (mean ± SD; age 23 ± 3 yr) completed three conditions on a cycle ergometer: 1) HIIT with passive recovery periods between four bouts (HIITPASS) 2) HIIT with active recovery periods between four bouts (HIITACT) 3) HIITACT with four HIIT bouts replaced with passive periods (REC). Deoxygenated haemoglobin (HHb) in the vastus lateralis (VL) and gastrocnemius (GN) muscles and the pre-frontal cortex (FH), oxygen consumption (VO2), power output and heart rate (HR) were measured continuously during the three conditions.

RESULTS

There was a significant increase in HHb at VL during bouts 2 (p = 0.017), 3 (p = 0.035) and 4 (p = 0.035) in HIITACT, compared to HIITPASS. Mean power output was significantly lower in HIITACT, compared to HIITPASS (p < 0.001). There was a significant main effect for site in both HIITPASS (p = 0.029) and HIITACT (p = 0.005). There were no significant differences in VO2 and HR between HIITPASS and HIITACT.

CONCLUSIONS

The increase in HHb at VL and the lower mean power output during HIITACT could indicate that a higher level of deoxygenation contributes to decreased mechanical power in sedentary participants. The significant differences in HHb between sites indicates the specificity of oxygen utilisation.

An integrated view on the oxygenation responses to incremental exercise at the brain, the locomotor and respiratory muscles

In the past two decades oxygenation responses to incremental ramp exercise, measured non-invasively by means of near-infrared spectroscopy at different locations in the body, have advanced the insights on the underpinning mechanisms of the whole-body pulmonary oxygen uptake ([Formula: see text]) response. In healthy subjects the complex oxygenation responses at the level of locomotor and respiratory muscles, and brain were simplified and quantified by the detection of breakpoints as a deviation in the ongoing response pattern as work rate increases. These breakpoints were located in a narrow intensity range between 75 and 90 % of the maximal [Formula: see text] and were closely related to traditionally determined thresholds in pulmonary gas exchange (respiratory compensation point), blood lactate measurements (maximal lactate steady state), and critical power. Therefore, it has been assumed that these breakpoints in the oxygenation patterns at different sites in the body might be equivalent and could, therefore, be used interchangeably. In the present review the typical oxygenation responses (at locomotor and respiratory muscle level, and cerebral level) are described and a possible framework is provided showing the physiological events that might link the breakpoints at different body sites with the thresholds determined from pulmonary gas exchange and blood lactate measurements. However, despite a possible physiological association, several arguments prevent the current practical application of these breakpoints measured at a single site as markers of exercise intensity making it highly questionable whether measurements of the oxygenation response at one single site can be used as a reflection of whole-body responses to different exercise intensities.

Aerobic training enhances muscle deoxygenation in early post-myocardial infarction

Purpose

Exercise-induced skeletal muscle deoxygenation is startling by its absence in early post-myocardial infarction (MI) patients. Exercise training early post-MI is associated with reduced cardiovascular risk and increased aerobic capacity. We therefore investigated whether aerobic training could enhance the muscle deoxygenation in early post-MI patients.

Methods

21 ± 8 days after the first MI patients (n = 16) were divided into 12-week aerobic training (TR, n = 10) or non-training (CON, n = 6) groups. Before and after intervention, patients performed ramp bicycle exercise until exhaustion. Muscle deoxygenation was measured at vastus lateralis by near-infrared spectroscopy during exercise.

Results

Aerobic training significantly increased peak oxygen uptake (VO₂) (18.1 ± 3.0 vs. 22.9 ± 2.8 mL/kg/min), decreased the change in muscle oxygen saturation from rest to submaximal and peak exercise (∆SmO₂; 2.4 ± 5.7 vs. −7.0 ± 3.4 %), and increased the relative change in deoxygenated hemoglobin/myoglobin concentration from rest to submaximal (−1.5 ± 2.3 vs. 3.0 ± 3.6 μmol/L) and peak exercise (1.1 ± 4.5 vs. 8.2 ± 3.5 μmol/L). Change in total hemoglobin/myoglobin concentration in muscle was not significantly affected by training. In CON, no significant alterations were found after 12 weeks in either muscle deoxygenation or peak VO₂ (18.6 ± 3.8 vs. 18.9 ± 4.6 mL/kg/min). An increase in peak VO₂ was significantly negatively correlated with change in ∆SmO₂ (r = −0.65) and positively associated with change in ∆deoxy-Hb/Mb at peak exercise (r = 0.64) in TR.

Conclusions

In early post-MI patients, aerobic training enhanced skeletal muscle deoxygenation, and the enhancement was related to increased aerobic capacity.

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 ± 0.14 m.s(-1)) but not the CON group (pre = 5.37 ± 0.27 to 5.39 ± 0.30 m.s(-1)) significant changes were seen in the 30-15 IFT 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 ± 26.48 μM.cm); and ΔHbO2+ MbO2 (-74.29 ± 13.82 to -109.36 ± 22.61 μM.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.

Improvements in exercise performance with high-intensity interval training coincide with an increase in skeletal muscle mitochondrial content and function

Six sessions of high-intensity interval training (HIT) are sufficient to improve exercise capacity. The mechanisms explaining such improvements are unclear. Accordingly, the aim of this study was to perform a comprehensive evaluation of physiologically relevant adaptations occurring after six sessions of HIT to determine the mechanisms explaining improvements in exercise performance. Sixteen untrained (43 ± 6 ml·kg−1·min−1) subjects completed six sessions of repeated ( 8 – 12 ) 60 s intervals of high-intensity cycling (100% peak power output elicited during incremental maximal exercise test) intermixed with 75 s of recovery cycling at a low intensity (30 W) over a 2-wk period. Potential training-induced alterations in skeletal muscle respiratory capacity, mitochondrial content, skeletal muscle oxygenation, cardiac capacity, blood volumes, and peripheral fatigue resistance were all assessed prior to and again following training. Maximal measures of oxygen uptake (V̇o2peak; ∼8%; P = 0.026) and cycling time to complete a set amount of work (∼5%; P = 0.008) improved. Skeletal muscle respiratory capacities increased, most likely as a result of an expansion of skeletal muscle mitochondria (∼20%, P = 0.026), as assessed by cytochrome c oxidase activity. Skeletal muscle deoxygenation also increased while maximal cardiac output, total hemoglobin, plasma volume, total blood volume, and relative measures of peripheral fatigue resistance were all unaltered with training. These results suggest that increases in mitochondrial content following six HIT sessions may facilitate improvements in respiratory capacity and oxygen extraction, and ultimately are responsible for the improvements in maximal whole body exercise capacity and endurance performance in previously untrained individuals.

High-intensity interval training in stroke rehabilitation

After stroke, people with weakness enter a vicious cycle of limited activity and deconditioning that limits functional recovery and exacerbates cardiovascular risk factors. Conventional aerobic exercise improves aerobic capacity, function, and overall cardiometabolic health after stroke. Recently, a new exercise strategy has shown greater effectiveness than conventional aerobic exercise for improving aerobic capacity and other outcomes among healthy adults and people with heart disease. This strategy, called high-intensity interval training (HIT), uses bursts of concentrated effort alternated with recovery periods to maximize exercise intensity. Three poststroke HIT studies have shown preliminary effectiveness for improving functional recovery. However, these studies were varied in approach and the safety of poststroke HIT has received little attention. The objectives of this narrative review are to (1) propose a framework for categorizing HIT protocols; (2) summarize the safety and effectiveness evidence of HIT among healthy adults and people with heart disease and stroke; (3) discuss theoretical mechanisms, protocol selection, and safety considerations for poststroke HIT; and (4) provide directions for future research.