Submaximal Trials Research Articles

Effect of Caffeine and Nitrates Combination on Exercise Performance, Heart Rate and Oxygen Uptake: A Systematic Review and Meta-Analysis.

The evidence about the synergy of combining caffeine (CAF) and nitrates on exercise performance has not been summarized, although there is a possibility of additive/synergistic effects of the co-ingestion of these substances given their different mechanisms of action in central (CAF) and peripheral tissues (nitrates). The aim was to analyze the effects of co-supplementation of CAF and nitrates on sports performance in comparison to the isolated ingestion of these substances. The databases of PubMed, Web of Science, Medline, CiNAHL and SPORTDiscus were used until June 2024 following PRISMA guidelines. Randomized controlled trials, at least one single-blind trial, conducted in adults were considered. A meta-analysis was performed using the random effects model to calculate the standardized mean difference estimated by Hedges' g and 95% confidence intervals (CIs) for studies with four arms. Six studies were included (N = 95). The meta-analysis revealed that caffeine and nitrates supplementation (CAF+nitrates) did not enhance performance in time trials (TTs) over the CAF alone (g = -0.06; 95% CI = -0.46 to 0.35; p = 0.78) or nitrates alone (g = 0.29; 95% CI = -0.12 to 0.70; p = 0.17). CAF+nitrates did not affect heart rate during submaximal exercise trials over CAF alone (g = 0.04; 95% CI = -0.31 to 0.40; p = 0.80) or nitrates alone (g = -0.15; 95% CI = -0.50 to 0.20; p = 0.40). Likewise, CAF+nitrates did not affect oxygen uptake during submaximal exercise trials over CAF alone (g = -0.04; 95% CI = -0.45 to 0.37; p = 0.84) or nitrates alone (g = -0.29; 95% CI = -0.70 to 0.12; p = 0.16). CAF+nitrates did not offer further benefits on exercise performance or physiological variables from the isolated intake of CAF and nitrates.

Effects of Acute Beetroot Juice Supplementation and Exercise on Cardiovascular Function in Healthy Men in Preliminary Study: A Randomized, Double-Blinded, Placebo-Controlled, and Crossover Trial.

Nitrate-rich beetroot juice (NRBRJ) can potentially enhance exercise performance and improve cardiovascular function, leading to an increased use of NRBRJ over the years. However, the combined effects of NRBRJ supplementation and exercise on cardiovascular function remain unclear. Therefore, this study compared cardiovascular function responses to submaximal exercise with either placebo (PLA) or NRBRJ supplementation in healthy men. Twelve healthy men (aged 25.2 ± 2.3 years) completed the 30-min submaximal cycle ergometer exercise trials corresponding to 70% maximal heart rate (HRmax) with either PLA or NRBRJ supplementation in a random order. The mean exercise load, heart rate (HR), stroke volume (SV), cardiac output (CO), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and total peripheral resistance (TPR) were measured during exercise. The brachial-ankle pulse wave velocity (baPWV) and flow-mediated dilation (FMD) were measured before and after exercise. NRBRJ supplementation was more effective than PLA in increasing the mean exercise load and decreasing DBP and MAP during submaximal exercise. Furthermore, baPWV decreased in the NRBRJ trial and was considerably lower after exercise in the NRBRJ-supplemented group than in the PLA-supplemented group. FMD significantly increased in the PLA and NRBRJ trials; however, NRBRJ supplementation demonstrated a significantly higher FMD before and after exercise than PLA supplementation. In conclusion, acute NRBRJ supplementation and exercise were more effective than PLA supplementation and exercise in improving aerobic exercise capacity and cardiovascular function in healthy men.

Impact of Respiratory Muscle Training on Exercise Tolerance in Hypobaric Hypoxia

Hypoxia and certain chronic diseases can intensify the work of breathing, potentially impacting the muscle hyperemic response during exercise and overall exercise performance. Respiratory muscle training (RMT) has been observed to decrease perceived effort under hypoxic conditions; however, it remains unclear if RMT boosts exercise performance in acute hypoxia. We investigated whether 4 weeks of RMT could enhance maximal and submaximal exercise performance in hypoxia (PB=425 mmHg, ~4876 m). Seven adult males underwent a 250 kJ submaximal (RPE 15-17) cycling trial in hypoxia, followed by an incremental test to maximal exertion. After 4 weeks of RMT under normoxic conditions, these tests were repeated in hypoxia. Although six of the participants displayed improvements in submaximal exercise performance, these numerical differences failed to reach statistical significance. However, RMT did raise VO2max peak power (Pre-RMT: 242.62 ± 35, Post-RMT: 251.85 ± 38 W, p=0.04). Moreover, even with an increased HR during the submaximal exercise trial after RMT (Pre-RMT:154.14 ± 16, Post-RMT: 160.86 ± 12, p<0.05), the RPE showed no significant difference during the test (Pre-RMT: 17.43 ± 0.79, Post-RMT: 17.43 ± 0.53, P>0.05). Despite this, no substantial increase in hypoxic submaximal exercise performance was observed, likely due to the small sample size. These findings suggest RMT might increase hypoxic exercise tolerance by reducing perceived exertion for a given HR. This work was supported by funding from the United States Special Operations Command (USSOCOM) and the National Institutes of Health (2L30HL134123-03). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Influence of intellectual disability on exercise regulation: exploring verbal, auditory and visual guidance to contribute to promote inclusive exercise environments

ObjectiveThe role of intellectual disability (ID) in exercise regulation has remained largely unexplored, yet recent studies have indicated cognitive-related impaired pacing skills in people with ID. In a well-controlled laboratory...

Persistent Contralateral Pain Compromises Exercise Tolerance but Does not Alter Corticomotor Responses During Repeated, Submaximal Isometric Knee Extensions to Task Failure

Muscle pain is an important determinant of exercise tolerance, but its relationship with neurophysiological responses during a submaximal exercise trial is unclear. The purpose of this study was to determine the effect of persistent contralateral pain on neurophysiological function and perceptual responses during ipsilateral isometric knee extensions to task failure. Ten participants performed a single-leg repeated submaximal isometric knee extensions with (PAIN) or without (CTRL) constant pain induced by intermittent blood flow occlusion combined with evoked muscle contraction applied to the contralateral, resting leg. Transcranial magnetic stimulation (TMS) applied over the motor cortex was used to assess corticospinal excitability (quantified as motor evoked potentials), corticospinal inhibition (quantified as silent period duration), and short interval intracortical inhibition. Maximal voluntary contractions (MVCs), coupled with femoral nerve stimulation to the exercising leg, were performed every 12 submaximal contractions to assess neuromuscular function. Perceived leg pain and effort were also assessed throughout the exercise. The experimental pain shortened the time to task failure compared to CTRL (P = 0.019). Although time effects were present, no differences appeared between conditions for MVC force, voluntary activation, or potentiated twitch force across both tasks (all P > 0.05). Additionally, no differences between CTRL and PAIN were demonstrated for any TMS-derived measures assessing corticospinal responses. Exercising leg pain was higher in CTRL (P = 0.018), as was perceived exertion (P = 0.030). Overall, when using a persistent, submaximal experimental pain intervention, it appears that although muscle pain compromises exercise tolerance, this phenomenon occurs independently of potential alterations in corticomotor mechanisms.

Do poles really "save the legs" during uphill pole walking at different intensities?

In sky- and trail-running competitions, many athletes use poles. The aims of this study were to investigate whether the use of poles affects the force exerted on the ground at the feet (Ffoot), cardiorespiratory variables and maximal performance during uphill walking. Fifteen male trail runners completed four testing sessions on different days. On the first two days, they performed two incremental uphill treadmill walking tests to exhaustion with (PWincr) and without poles (Wincr). On the following days, they performed submaximal and maximal tests with (PW80 and PWmax) and without (W80 and Wmax) poles on an outdoor trail course. We measured cardiorespiratory parameters, the rating of perceived exertion, the axial poling force and Ffoot. When walking on the treadmill, we found that poles reduced maximum Ffoot (- 2.8 ± 6.4%, p = 0.03) and average Ffoot (- 2.4 ± 3.3%, p = 0.0089). However, when outdoors, we found pole effect only for average Ffoot (p = 0.0051), which was lower when walking with poles (- 2.6 ± 3.9%, p = 0.0306 during submaximal trial and - 5.21 ± 5.51%, p = 0.0096 during maximal trial). We found no effects of poles on cardiorespiratory parameters across all tested conditions. Performance was faster in PWmax than in Wmax (+ 2.5 ± 3.4%, p = 0.025). The use of poles reduces the foot force both on the treadmill and outdoors at submaximal and maximal intensities. It is, therefore, reasonable to conclude that the use of poles "saves the legs" during uphill without affecting the metabolic cost.

Unraveling the Role of (Meta-) Cognitive Functions in Pacing Behavior Development during Adolescence: Planning, Monitoring, and Adaptation.

This study aimed to investigate whether (meta-) cognitive functions underpin the development of the self-regulated distribution of effort during exercise (i.e., pacing) throughout adolescence. Participants included 18 adolescents (9 girls, 15.6 ± 2.5 yr old) and 26 adults (13 women, 26.8 ± 3.1 yr old), all recreationally active but unfamiliar with time trial cycling. The (meta-) cognitive functions involved in preexercise planning were quantified by calculating the difference between estimated and actual finish time during a 4-km cycling time trial. The capability to monitor and adapt one's effort distribution during exercise was measured during a 7-min submaximal trial, in which the participants were tasked with adhering to a set submaximal goal velocity either with (0-5 min) or without (5-7 min) additional feedback provided by the researcher. Analyses included between-group comparisons (ANOVA) and within-group comparisons (correlation) ( P < 0.05). Adolescents were less accurate in their estimation of the task duration. The adolescents' overestimation of task duration of the 4-km time trial was accompanied by pacing behavior characteristics resembling a longer trial (i.e., more even power output distribution, lower RPE, more pronounced end-spurt). Contrary to the adults, the adolescents deviated relatively more from the goal velocity during the 7-min submaximal trial, when no additional feedback was provided by the researcher. Within the adolescent group, estimation of task duration accuracy ( r = 0.48) and adherence to goal velocity ( r = 0.59) correlated with age. The (meta-) cognitive functions involved in the preexercise planning and the monitoring and adaptation of the distribution of effort during exercise underpin the development of pacing behavior during adolescence. Feedback from the (social) environment can be used to aid the monitoring and adaptation of effort expenditure in adolescents.

A Double-Blind, Randomized, Placebo-Controlled Pilot Study examining an Oxygen Nanobubble Beverage for 16.1-km Time Trial and Repeated Sprint Cycling Performance

There is growing interest of ergogenic aids that deliver supplemental oxygen during exercise and recovery, however, breathing supplemental oxygen via specialist facemasks is often not feasible. Therefore, this study investigated the effect of an oxygen-nanobubble beverage during submaximal and repeated sprint cycling. In a double-blind, randomized, placebo-controlled study, 10 male cyclists (peak aerobic capacity, 56.9 ± 6.1 mL·kg−1·min−1; maximal aerobic power, 385 ± 25 W) completed submaximal or maximal exercise after consuming an oxygen-nanobubble (O2) or placebo (PLA) beverage. Submaximal trials comprised 30-min of steady-state cycling at 60% peak aerobic capacity and 16.1-km time-trial (TT). Maximal trials involved 4 × 30 s Wingate tests interspersed by 4-min recovery. Time-to-completion during the 16.1-km TT was 2.4% faster after O2 compared with PLA (95% CI = 0.7–4.0%, p = 0.010, d = 0.41). Average power for the 16.1-km TT was 4.1% higher for O2 vs. PLA (95% CI = 2.1–7.3%, p = 0.006, d = 0.28). Average peak power during the repeated Wingate tests increased by 7.1% for O2 compared with PLA (p = 0.002, d = 0.58). An oxygen-nanobubble beverage improves performance during submaximal and repeated sprint cycling, therefore may provide a practical and effective ergogenic aid for competitive cyclists.

Horizontal Foot Speed During Submaximal and Maximal Running.

Horizontal foot speed is fundamental for running synchronization and stability, and may also be important for sprinting performance. In this investigation, we quantified the following during steady-speed running: (a) peak forward foot speed during the swing phase, (b) backward foot speed at touchdown, and (c) ground speed difference (GSD), i.e., the difference between forward running speed and backward foot speed at touchdown. We hypothesized that forward and backward foot speed would be significantly and positively correlated with top speed, and that GSD would be significantly and negatively correlated with top speed. Participants (20 male, 20 female) completed 40-m submaximal and maximal-effort running trials, with kinematic data collected from 31-39 m. Across top speed trials, forward foot speed (r = 0.90, p < 0.001) and backward foot speed (r = 0.85, p < 0.001) were significantly and positively correlated with running speed. However, counter to expectations, GSD values slightly increased with top speed (r = 0.36, p = 0.027). These findings indicate that forward and backward foot speeds are important variables for sprinting performance, but faster runners may not necessarily exhibit lower GSD values at top speed.

Pulmonary ventilation and gas exchange during prolonged exercise in humans: Influence of dehydration, hyperthermia and sympathoadrenal activity.

What is the central question of the study? Ventilation increases during prolonged intense exercise, but the impact of dehydration and hyperthermia, with associated blunting of pulmonary circulation, and independent influences of dehydration, hyperthermia and sympathoadrenal discharge on ventilatory and pulmonary gas exchange responses remain unclear. What is the main finding and its importance? Dehydration and hyperthermia led to hyperventilation and compensatory adjustments in pulmonary CO2 and O2 exchange, such that CO2 output increased and O2 uptake remained unchanged despite the blunted circulation. Isolated hyperthermia and adrenaline infusion, but not isolated dehydration, increased ventilation to levels similar to combined dehydration and hyperthermia. Hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise, partly via sympathoadrenal activation. The mechanisms driving hyperthermic hyperventilation during exercise are unclear. In a series of retrospective analyses, we evaluated the impact of combined versus isolated dehydration and hyperthermia and the effects of sympathoadrenal discharge on ventilation and pulmonary gas exchange during prolonged intense exercise. In the first study, endurance-trained males performed two submaximal cycling exercise trials in the heat. On day 1, participants cycled until volitional exhaustion (135± 11min) while experiencing progressive dehydration and hyperthermia. On day 2, participants maintained euhydration andcore temperature (Tc ) during a time-matched exercise (control). At rest and during the first 20min of exercise, pulmonary ventilation ( ), arterial blood gases, CO2 output and O2 uptake were similar in both trials. At 135±11min, however, was elevated with dehydration and hyperthermia, and this was accompanied by lower arterial partial pressure of CO2 , higher breathing frequency, arterial partial pressure of O2 , arteriovenous CO2 and O2 differences, and elevated CO2 output and unchanged O2 uptake despite a reduced pulmonary circulation. The increased was closely related to the rise in Tc and circulating catecholamines (R2 ≥0.818, P≤0.034). In three additional studies in different participants, hyperthermia independently increased to an extent similar to combined dehydration and hyperthermia, whereas prevention of hyperthermia in dehydrated individuals restored to control levels. Furthermore, adrenaline infusion during exercise elevated both Tc and . These findings indicate that: (1) adjustments in pulmonary gas exchange limit homeostatic disturbances in the face of a blunted pulmonary circulation; (2) hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise; and (3) sympathoadrenal activation might partly mediate the hyperthermic hyperventilation.

The Effects of an External Equine Nasal Strip on Thermoregulation During Exercise

The purpose of this study was to examine the effects of an external nasal strip on thermoregulation during submaximal exercise in Standardbred horses. While several studies have been conducted to determine the effects of the external nasal strip on airway resistance, exercise induced pulmonary hemorrhage, gas exchange, and time to fatigue in maximally exercising horses, the effects of the nasal strip on equine thermoregulation have not yet been examined. It was hypothesized that the application of an external nasal strip would alter central venous temperature (Tcore), skin temperature (Tskin), and exercise time to reach a central venous temperature of 40 °C. Eight mature Standardbred horses each performed two submaximal exercise trials, one with a nasal strip (NS), and one without (control), on a high-speed equine treadmill with exercise concluding upon Tcore reaching 40 °C. There were no significant differences in Tcore or Tskin between the NS and control groups during pre-exercise, exercise or recovery (P > .05), nor were there differences (P > .05) in exercise time to reach a Tcore of 40 °C (NS: 11.8 ± 1.5 minutes; Control: 11.5 ± 1.1 min). We conclude that the application of an external nasal strip does not affect the equine thermoregulatory response during submaximal exercise.

Ratings of perceived exertion from a submaximal 20-m shuttle run test predict peak oxygen uptake in children and the test feels better

PurposeTo determine the validity and test–retest reliability of using ratings of perceived exertion (RPE) elicited during a submaximal 20-m Shuttle Run Test (20mSRT) to predict VO2peak in children and investigate acute affective responses.MethodsTwenty-five children (14 boys; age, 12.8 ± 0.7 years; height, 162.0 ± 9.3 cm; mass, 49.9 ± 7.7 kg) completed four exercise tests (GXT, 2 submaximal 20mSRT, maximal 20mSRT). The Eston–Parfitt RPE scale was used, and affect was measured with the Feeling Scale. Submaximal 20mSRT were terminated upon participants reporting RPE7. The speed-RPE relationship from the submaximal 20mSRTs was extrapolated to RPE9 and 10 to predict peak speed and then used to estimate VO2peak.ResultsRepeated measures ANOVA to examine the validity of using submaximal RPE to predict VO2peak resulted in a Gender main effect (boys = 46.7 ± 5.1 mL kg−1 min−1; girls = 42.0 ± 5.1 mL kg−1 min−1) and Method main effect (p < 0.01). There were significant differences between measured and estimated VO2peak from the maximal 20mSRT, but not between measured and estimated VO2peak at RPE9 and RPE10. Intraclass correlation analysis revealed excellent reliability (~ 0.9) between the two submaximal 20mSRTs. Significant differences (p < 0.05) in end-test affect were reported between submaximal and maximal trials in girls, but not in boys, with girls feeling less negative at the end of the submaximal trials.ConclusionsThe results of this study provide evidence that RPE reported during a submaximal 20mSRT can be used to predict VO2peak accurately and reliably. In this study, the submaximal 20mSRT ending at RPE7, provided better predictions of VO2peak while minimising aversive end-point affect, especially in girls.

Reliability of Upper-Extremity Muscle Activity and Kinematics During Adaptive Rowing.

The purpose of this study was to determine test-retest reliability of upper-extremity muscle activity and kinematics during submaximal adapted rowing. A repeated-measures design was used. Data were collected on 10 individuals (7 male and 3 female) with mobility impairment. Surface electromyography of muscles of the dominant arm (upper, middle, and lower trapezius, anterior and posterior deltoid, latissimus dorsi, and infraspinatus) was acquired. Muscle activity was analyzed using the area under the curve, peak amplitude, and mean amplitude. Kinematic analysis determined joint motions for shoulder plane and angle of elevation, and trunk flexion/extension, and rotation at the catch (0%) and finish (100%) of the stroke. Three submaximal rowing trials (20 strokes each) were completed with the middle 10 strokes of each trial averaged for analysis. An interclass correlation coefficient (3, 10) determined test-retest reliability across trials (interclass correlation coefficient defined as poor < .5; moderate .5-.75; and good .75-.9). Moderate to excellent reliability existed across all muscles for the area under the curve, peak amplitude, and mean amplitude. Excellent reliability was seen for all kinematic measures. Results indicate upper-extremity muscle activity and kinematics of the adapted rowing stroke are reliable in a diverse group of individuals with mobility impairment.

Perceived Exertion And Dyspnea While Cycling During A Hypoxic And Hyperoxic Placebo

Rating of Perceived Exertion (RPE) is used to subjectively quantify and monitor the perception of physical activity, breathlessness or dyspnea, and leg discomfort (RPElegs) during exercise. However, it is unknown how perceptions of exertion can be influenced by expectation of difficulty. PURPOSE: We asked if the placebo and nocebo effects could alter dyspnea and RPEleg by telling subjects they were receiving different concentrations of oxygen during exercise. We hypothesized that subjects would rate their dyspnea and RPElegs higher when they believed they were breathing hypoxic gas and lower when they believed they were breathing hyperoxic gas relative to room air. METHODS: Thirty healthy, active subjects (19 M, 11 F) with normal pulmonary function participated. Prior to exercise, we read a script to ensure subjects understood hypoxic and hyperoxic gas might make breathing feel more difficult and easier, respectively, but intentionally made no mention about RPEleg. Then during 5-minute submaximal cycling trials (60% peak work rate), we deceived subjects by telling them they were breathing different hypoxic (17% and 15% O2) and hyperoxic (23% O2) gas concentrations, when in fact they breathed room air (21% O2). At the end of each trial, we asked subjects for their dyspnea and RPEleg. RESULTS: Cardiorespiratory variables were similar between the trials, however dyspnea and RPElegs changed in a dose-response manner depending on the O2 concentration participants believed they breathed. When subjects believed they were breathing 15% O2, they significantly increased their dyspnea +0.70 ± 0.2 Borg units (p = 0.03) compared to room air, whereas RPElegs did not significantly change +0.35 ± 0.1 Borg units (p = 0.70). When comparing the most severe hypoxic condition, 15% O2, to the 23% hyperoxic condition, subjects significantly increased their dyspnea +1.05 ± 0.4 Borg units (p = 0.003) but did not significantly change RPElegs + 0.55 ± 0.2 Borg units (p = 0.46). CONCLUSION: We found that dyspnea during exercise is susceptible to expectancy, without any accompanying physiological changes. Given that a single unit in dyspnea is considered a minimal clinically important difference, our findings show that the effect of expectation must be considered when interpreting sensations of breathlessness. Support: NSERC

Variability Of Motor Performance Over Multiple Maximal Effort Trials Increases Post-stroke

INTRODUCTION: The ability to regulate force during a single trial of a submaximal motor task has shown to be more variable post-stroke. The degree to which chronic stroke survivors’ force output fluctuates during a single submaximal trial is negatively correlated with multiple functional measures, including strength and walking speed. However, the variability of performance among different attempts of a maximal motor task remains unclear. Relevant to rehabilitation, other groups have shown that older adults can be trained to decrease fluctuations in force output. PURPOSE: 1) To quantify variability in motor performance over multiple attempts of the same maximal motor task in stroke survivors and compare to neurologically intact controls; 2) To investigate relationships between motor performance variability and functional measurements. METHODS: Nineteen chronic stroke survivors (at least 6 months post stroke, 11 F, aged 60 +/- 13 years) and fourteen controls (8 F, aged 62 +/- 10 years) performed five to seven maximal efforts of voluntary isometric knee extension using either the paretic (stroke) or the dominant (control) leg with both visual feedback and verbal encouragement. The peak value obtained from the series of maximal efforts was used as maximal voluntary isometric contraction (MVIC) of the knee extensors. Variability of the MVICs was calculated as the coefficient of variation (COV), which represents the ratio of the standard deviation to the mean value of torque output during different maximal attempts. RESULTS: COV during multiple trials of maximal-effort motor tasks significantly increases post-stroke as compared to controls (8.7 ± 5.4% vs 5.3 ± 2.8%, p = 0.04). COV was negatively correlated with age (R2 = -0.63) in controls but not stroke (R2 < 0.01). Relevant to motor performance, COV is negatively correlated with the lower extremity motor subscale of the Fugl-Meyer Assessment (FMA, R2 = -0.56) excluding participants in the upper quartile of FMA scores. CONCLUSION: Stroke survivors, regardless of age, are more variable in their motor performance at maximal efforts as compared to controls. This may be exacerbated in individuals who have more difficulty individuating joint movements. These data support the use of multiple attempts when evaluating maximal strength in the clinic or research laboratories.

Perceived exertion and dyspnea while cycling during a hypoxic and hyperoxic placebo.

Rating of perceived exertion (RPE) is used to subjectively quantify the perception of physical activity, breathlessness or dyspnea, and leg discomfort (RPElegs) during exercise. However, it is unknown how dyspnea or RPElegs can be influenced by expectations. Thirty healthy, active participants (19males, 11females) completed five, 5-minute submaximal cycling trials at 60% peak work rate. We deceived participants by telling them they were inspiring different hypoxic and hyperoxic gases, when in fact they breathed room air. Cardiorespiratory variables were similar between the trials, however, dyspnea and RPElegs evaluated with a Borg scale changed in a dose-response manner. When participants believed they were breathing 15% O2, they significantly increased dyspnea+0.70±0.2 units (p=0.03) compared to room air, whereas RPElegs was unchanged+0.35±0.1 units (p=0.70). When participants believed they were breathing 15% O2, they significantly increased dyspnea+1.05 ± 0.4 units (p=0.003) compared to 23% hyperoxic condition, whereas RPElegs was unchanged+0.35±0.1 units (p=0.70). We found that dyspnea during exercise is susceptible to expectancy, without any accompanying physiological changes. Given coaches and clinicians use perceived exertion to prescribe exercise intensity and evaluate treatments, our findings show that the effect of expectations must be considered when interpreting sensations of breathlessness.

Comparison of the arm-stroke kinematics between maximal and sub-maximal breaststroke swimming using discrete data and time series analysis

The aim of the current study was to compare the arm-stroke kinematics during maximal and sub-maximal breaststroke swimming using both discrete and continuous data analysis. Nine male breaststrokers swam 2 × 25 m with maximal and sub-maximal intensity and their full body 3-D kinematics were obtained using eight video cameras. The arm-stroke was divided into five phases: recovery, glide, out-sweep, in & down-sweep and in & up-sweep. The statistical treatment of selected discrete variables was conducted using t-test, while the analysis of their equivalent time series, when applicable, was conducted using Statistical Parametric Mapping. Sub-maximal trial, compared to maximal, presented lower swimming velocity, greater stroke length and less stroke rate. Moreover, the absolute and relative duration of the glide phase was longer, while the relative duration of all the other phases was shorter. The resultant hand velocity during the arm recovery was slower, as well as the hand velocity time series in the transverse and longitudinal axis which were slower from ∼ 45 % to ∼ 60 % and from ∼ 5 % to ∼ 15 % of the stroke cycle, respectively. Both discrete and continuous data analysis revealed that the main discriminating factor between the two conditions concerns to the adjustment of the glide and the recovery phase and consequently the continuation of the propulsive movements.

Alterations in shoulder kinematics are associated with shoulder pain during wheelchair propulsion sprints.

The study purpose was to examine the biomechanical characteristics of sports wheelchair propulsion and determine biomechanical associations with shoulder pain in wheelchair athletes. Twenty wheelchair court‐sport athletes (age: 32 ± 11 years old) performed one submaximal propulsion trial in their sports‐specific wheelchair at 1.67 m/s for 3 min and two 10 s sprints on a dual‐roller ergometer. The Performance Corrected Wheelchair User's Shoulder Pain Index (PC‐WUSPI) assessed shoulder pain. During the acceleration phase of wheelchair sprinting, participants propelled with significantly longer push times, larger forces, and thorax flexion range of motion (ROM) than both the maximal velocity phase of sprinting and submaximal propulsion. Participants displayed significantly greater peak glenohumeral abduction and scapular internal rotation during the acceleration phase (20 ± 9° and 45 ± 7°) and maximal velocity phase (14 ± 4° and 44 ± 7°) of sprinting, compared to submaximal propulsion (12 ± 6° and 39 ± 8°). Greater shoulder pain severity was associated with larger glenohumeral abduction ROM (r = 0.59, p = 0.007) and scapular internal rotation ROM (r = 0.53, p = 0.017) during the acceleration phase of wheelchair sprinting, but with lower peak glenohumeral flexion (r = −0.49, p = 0.030), peak abduction (r = −0.48, p = 0.034), and abduction ROM (r = −0.44, p = 0.049) during the maximal velocity phase. Biomechanical characteristics of wheelchair sprinting suggest this activity imposes greater mechanical stress than submaximal propulsion. Kinematic associations with shoulder pain during acceleration are in shoulder orientations linked to a reduced subacromial space, potentially increasing tissue stress.

Reliability and validity of the Stryd Power Meter during different walking conditions

BackgroundThe Styrd Power Meter is gaining special interest for on-field gait analyses due to its low-cost and general availability. However, the reliability and validity of the Stryd during walking on positive slopes using different backpack loads have never been investigated. Research questionIs the Stryd Power Meter reliable and valid for quantifying gait mechanics during walking on positive inclines and during level walking incorporating load carriage? MethodsSeventeen participants from a police force rescue team performed 8 submaximal walking trials for 5-min at 3.6 km·h−1 during different positive slope (1%, 10% and 20%) and backpack load (0%, 10%, 20%, 30% and 40% of body mass) conditions. Two Stryd devices were utilized for reliability analyses. Validity of cadence and ground contact time (GCT) were analyzed against a gold standard device (Optojump). ResultsThe Stryd demonstrated acceptable reliability [mean bias: < 2.5%; effect size (ES): < 0.25; standard error of the mean: < 1.7%; r: > 0.76] for power, cadence, and GCT. Validity measures (mean bias: <0.8%; ES: <0.07; r: >0.96; Lin’s Concordance Coefficient: 0.96; Mean Absolute Percent Error: <1%) for cadence were also found to be acceptable. The Stryd overestimated (P < 0.001; ES: >5.1) GCT in all the walking conditions. A significant systematic positive bias (P < 0.022; r = 0.56–0.76) was found in 7 conditions.Significance: The Stryd Power Meter appears to produce reliable measurements for power output, cadence and GCT. The Stryd produced valid measurements for cadence during walking on positive slopes and during level walking with a loaded backpack. However, the Stryd is not valid for measuring GCT during these walking conditions. This study adds novel data regarding the reliability and validity of this device and might be of particular interest for scientists, practitioners, and first responders seeking reliable devices to quantify gait mechanics during walking.

Effect of crank length on biomechanical parameters and muscle activity during standing cycling

ABSTRACT This study investigated the effect of crank length on biomechanical parameters and muscle activity during standing cycling. Ten participants performed submaximal cycling trials on a stand-up bicycle using four crank lengths. Joint angles, moments, powers, and works of the lower limbs were calculated from motion data and pedal reaction forces. Electromyographic (EMG) data were recorded from gluteus maximus (GM), vastus medialis, rectus femoris, biceps femoris (BF), gastrocnemius medialis, soleus, and tibialis anterior, and used to obtain the integrated EMG. Statistical parametric mapping was employed to analyse the biomechanical parameters throughout the pedalling cycle. Knee and hip flexion angles and hip power increased at the initiation (0–20%) of pedalling with increasing crank length, while the BF and GM muscle activities increased during propulsion (20–40%). Additionally, increasing the crank length resulted in increased knee power absorption during upstroke phase (70–100%). Peak knee extension moment increased with decreasing crank length during propulsion, but the moment at a short crank length during propulsion was comparable to fast walking. Consequently, longer crank lengths require increased propulsion power by the lower limb muscles during standing cycling compared to shorter crank lengths. Therefore, shorter crank lengths are recommended for stand-up bicycles to avoid fatigue.