Exercise Physiology

Journal of Science and Medicine in Sport, 2013

The critical power concept has been applied to constant-load exhaustive exercise and recently validated for 3-min all-out exercise. Objectives: To test the application of critical power to a 3-min all-out isokinetic cycling exercise. Design: Single-group, experimental, comparative design. Method: Nine participants performed a 3-min all-out isokinetic test and 4-5 constant-load exhaustive trials, at 60 and 100rpm, on an electrically-braked cycle. The linear P-t-1 relationship was modelled using a 2-parameter model (slope: critical power; intercept: Anaerobic Work Capacity). End power and accumulated work done above EP were calculated from the 3-min tests. Results: No significant difference and a significant correlation was found between end power and critical power (60rpm: 259±40W vs. 245±38W, P>0.05; r=0.85, P<0.01; 100rpm: 227±57W vs. 212±44W, P>0.05; r=0.86, P<0.01). The Bias±95% limits of agreement were 14±42W at 60rpm and 15±57W at 100rpm. Work done above EP (60rpm: 14.7±3.0kJ; 100rpm: 17.3±3.1kJ) was not significantly different to the anaerobic work capacity (60rpm: 16.2±3.2kJ; 100rpm: 20.6±6.4kJ; P>0.05) but with only a significant correlation at 60rpm (r=-0.71, P<0.05).

International Journal of Sports Medicine, 2019

The asymptote of the hyperbolic power-duration relationship, critical power (CP), demarcates sustainable from non-sustainable exercise. CP is a salient parameter within the theoretical framework determining exercise tolerance. However, measuring CP is time consumingtypically 4 constant-power exercise tests to intolerance, or a 3-min all-out sprint is required. PURPOSE To determine whether 30 s of maximal isokinetic cycling, immediately following the limit of tolerance, approximates CP. METHODS Fifteen participants (7 women, 8 men, 23±5 yr, 71±12 kg, V O2peak 4.39±1.04 L.min-1 ; 61±9 mL.kg.min-1) completed 4 constant supra-CP exercise tests to intolerance. Each test was followed immediately by a 30 s maximal isokinetic effort at 80 rpm. Mean isokinetic power was compared to the known CP. RESULTS Mean±SD CP was 159±47 W (CI95 133, 185 W). Maximal isokinetic power immediately following intolerance was greater (p<0.05) than CP in all but one comparison (181±51 vs 159±47 W; p>0.07). However, this closest estimation, following the longest duration constant-power test, resulted in 21 W of mean bias and wide limits of agreement (±84 W). CONCLUSIONS Isokinetic power measured immediately following intolerance consistently overestimated critical power. Thus, an adjunct of 30 s maximal isokinetic cycling immediately following the limit of tolerance does not approximate critical power. Abbreviations CCC, Lin's concordance correlation coefficient CI95, 95% confidence interval CP, critical power 2 Piso, isokinetic power W , curvature constant for the hyperbolic power-duration relationship V O2max, maximal oxygen uptake V O2peak, peak oxygen uptake

Respiratory Care, 2014

Background: Exercise capacity assessed by cardiopulmonary exercise testing is usually measured by peak oxygen consumption (peak V. O 2). However, not uncommonly, patients achieve a relatively higher Work load (peak Work) compared to their peak V. O 2. In these situations, it is difficult to know which parameter to use in assessing exercise capacity. The purpose of this study was to determine whether there are distinguishing physiological characteristics of patients with discordance between percent predicted peak Work vs. peak V. O 2 in order to understand how to use these measures in interpreting exercise capacity. Methods: We conducted a retrospective study of 172 cardiopulmonary exercise tests performed at our institution between 2003 and 2010. Subject characteristics were compared by ANOVA and multivariate logistic regression analysis. Results: The patients in the higher peak Work group demonstrated higher ventilatory efficiency (lower VE / V. CO 2 slope) and lung function (FEV 1 and FVC), a greater breathing reserve (higher BR, lower VE /MVV), and achieved a higher maximal heart rate. Patients in the higher max V. O 2 group were heavier, had lower ventilatory efficiency, and had a reduced breathing reserve. Multivariate logistic regression analysis showed that the predominant independent factors associated with group assignment were BMI, breathing reserve, and peak heart rate, with patients achieving higher percent

2016

A cardiopulmonary exercise test (CPX) can provide objective measures of exercise capacity. Specifically, incremental ramp exercise (IRE) and constant work-rate exercise (CWE) protocols are frequently used in clinical practice and for research. The CWE endurance time has shown larger increases than other indexes assessed by IRE after rehabilitation intervention. Muscle oxygen extraction is one of the important physiological factors of exercise capacity; however, the differences in muscle oxygen kinetics between IRE and CWE remain unclear. The purpose of this study was to compare the muscle oxygen kinetics during IRE and CWE. Each of the 15 participants performed IRE and CWE to exhaustion on a cycle ergometer. Ventilatory and muscle deoxygenation responses were measured during the tests; muscle deoxygenation was determined using near-infrared spectroscopy. No differences in oxygen uptake and heart rate were observed between the two tests. A comparison of the muscle deoxygenation kinet...

Applied Physiology, Nutrition, and Metabolism, 2016

We investigated whether muscle and ventilatory responses to incremental ramp exercise would be influenced by aerobic fitness status by means of a cross-sectional study with a large subject population. Sixty-four male students (age: 21.2 ± 3.2 years) with a heterogeneous peak oxygen uptake (51.9 ± 6.3 mL·min−1·kg−1, range 39.7–66.2 mL·min−1·kg−1) performed an incremental ramp cycle test (20–35 W·min−1) to exhaustion. Breath-by-breath gas exchange was recorded, and muscle activation and oxygenation were measured with surface electromyography and near-infrared spectroscopy, respectively. The integrated electromyography (iEMG), mean power frequency (MPF), deoxygenated [hemoglobin and myoglobin] (deoxy[Hb+Mb]), and total[Hb+Mb] responses were set out as functions of work rate and fitted with a double linear function. The respiratory compensation point (RCP) was compared and correlated with the breakpoints (BPs) (as percentage of peak oxygen uptake) in muscle activation and oxygenation. T...

2021

To establish whether very high-volume, high-intensity isometric exercise causes stress to the body and how it affects peripheral and central fatigue. Nineteen physically active healthy male subjects (21.2 ± 1.7 years; height – 1.82 ± 0.41 m, body weight – 79.9 ± 4.5 kg; body mass index – 24.3 ± 2.1 kg/m2) volunteered to participate in this study. They participated in two experiments 3–5 days apart. Each experiment comprised six series of 60-s maximum voluntary contraction (MVC) force (knee extension) achieved as rapidly as possible. This very high-volume, high-intensity exercise (HVHIE) was performed at different quadriceps muscle lengths: short (SL) and long (LL). The MVC and the electrically stimulated contractile properties of the muscle were measured prior to HVHIE, immediately after and 3 min after each series, and at 3, 10, and 30 min after the end of HVHIE. We found that HVHIE caused high levels of stress (cortisol levels approximately doubled, heart rate and the root mean sq...

The present study proposes an alternative way of comparing performance and acute physiological responses to continuous exercise with those of intermittent exercise, ensuring similar between-protocol overall effort (isoeffort) and the same total duration of exercise (isotime). This approach was expected to overcome some drawbacks of traditional methods of comparison. Fourteen competitive cyclists (2063 yrs) performed a preliminary incremental test and four experimental 30min self-paced protocols, i.e. one continuous and three passive-recovery intermittent exercise protocols with different workto-rest ratios (2 = 40:20s, 1 = 30:30s and 0.5 = 20:40s). A ''maximal session effort'' prescription was adopted for this experimental design. As expected, a robust perceived exertion template was observed irrespective of exercise protocol. Similar between-protocol pacing strategies further support the use of the proposed approach in competitive cyclists. Total work, oxygen uptake and heart rate mean values were significantly higher (P,0.05) in the continuous compared to intermittent protocols, while lactate values were lower. Manipulating the work-to-rest ratio in intermittent exercise, total work, oxygen uptake and heart rate mean values decreased with the decrease in the work-to-rest ratio, while lactate values increased. Despite this complex physiological picture, all protocols showed similar ventilatory responses and a nearly perfect relationship between respiratory frequency and perceived exertion. In conclusion, our data indicate that overall effort and total duration of exercise are two critical parameters that should both be controlled when comparing continuous with intermittent exercise. On an isoeffort and isotime basis, the work-to-rest ratio manipulation affects physiological responses in a different way from what has been reported in literature with traditional methods of comparison. Finally, our data suggest that during intermittent exercise respiratory frequency reflects physiological strain better than oxygen uptake, heart rate and blood lactate.

International journal of sports physiology and performance, 2016

The aim of the study was: a) to determine the effect of supramaximal exercise intensity, during constant work-rate cycling to exhaustion, on the accumulated oxygen deficit (AOD); and b) to determine the test-retest reliability of AOD. Twenty one trained male cyclists and triathletes (means ± standard deviation for age and maximal oxygen uptake (VO2max) were 41 ± 7 years and 4.53 ± 0.54 L·min-1, respectively) performed initial tests to determine the linear relationship between oxygen uptake (VO2) and power output, and VO2max. In subsequent trials, AOD was determined from exhaustive square-wave cycling trials at 105, 112.5 (in duplicate), 120 and 127.5% VO2max. Exercise intensity had an effect (P = 0.011) on the AOD (3.84 ± 1.11, 4.23 ± 0.96, 4.09 ± 0.87 and 3.93 ± 0.89 L at 105, 112.5, 120 and 127.5% VO2max, respectively). Specifically, AOD at 112.5% VO2max was greater than at 105% VO2max (P = 0.033) and at 127.5% VO2max (P = 0.022), but there were no differences between the AOD at 1...

Journal of Strength and Conditioning Research, 2018

This study aimed to evaluate oxygen uptake slow component (V _ O 2 sc) and mechanical economy/efficiency in half squat (HS) exercise during constant-load tests conducted at lactate threshold (LT) intensity. Nineteen healthy young men completed 3 HS exercise tests separated by 48-hour rest periods: 1 repetition maximum (1RM), incremental-load HS test to establish the %1RM corresponding to the LT, and constantload HS test at the LT. During the last test, cardiorespiratory, lactate, and mechanical responses were monitored. Fatigue in the lower limbs was assessed before and after the constantload test using a countermovement jump test. A slight and sustained increase of the V _ O 2 sc and energy expended (EE) was observed (p , 0.001). In blood lactate, no differences were observed between set 3 to set 21 (p. 0.05). A slight and sustained decrease of half squat efficiency and gross mechanical efficiency (GME) was detected (p , 0.001). Significant inverse correlations were observed between V _ O 2 and GME (r = 20.93, p , 0.001). Inverse correlations were detected between EE and GME (r = 20.94, p , 0.001). Significant losses were observed in jump height ability and in mean power output (p , 0.001) in response to the constant-load HS test. In conclusion, V _ O 2 sc and EE tended to rise slowly during constant-load HS exercise testing. This slight increase was associated with lowered efficiency throughout constant-load test and a decrease in jump capacity after testing. These findings would allow to elucidate the underlying fatigue mechanisms produced by resistance exercises in a constant-load test at LT intensity.

European Journal of Applied Physiology, 2007

The concept of VO2max has been a defining paradigm in exercise physiology for >75 years. Within the last decade, this concept has been both challenged and defended. The purpose of this study was to test the concept of VO2max by comparing VO2 during a second exercise bout following a preliminary maximal effort exercise bout. The study had two parts. In Study #1, physically active non-athletes performed incremental cycle exercise. After 1-min recovery, a second bout was performed at a higher power output. In Study #2, competitive runners performed incremental treadmill exercise and, after 3-min recovery, a second bout at a higher speed. In Study #1 the highest VO2 (bout 1 vs. bout 2) was not significantly different (3.95 + 0.75 vs. 4.06 + 0.75 l min-1). Maximal heart rate was not different (179 + 14 vs. 180 + 13 bpm) although maximal VE was higher in the second bout (141 + 36 vs. 151 + 34 l min-1). In Study #2 the highest VO2 (bout 1 vs. bout 2) was not significantly different (4.09 + 0.97 vs. 4.03 + 1.16 l min-1), nor was maximal heart rate (184 + 6 vs. 181 + 10 bpm) or maximal VE (126 + 29 vs. 126 + 34 l min-1). The results support the concept that the highest VO2 during a maximal incremental exercise bout is unlikely to change during a subsequent exercise bout,