Critical velocity of continuous and intermittent running exercise. An example of the limits of the critical power concept

Moderate- and High-Intensity Inspiratory Muscle Training Equally Improves Inspiratory Muscle Strength and Endurance-A Double-Blind Randomized Controlled Trial

BACKGROUND AND OBJECTIVE

Inspiratory muscle training (IMT) produced outstanding results in the physical performance of active subjects; however, little is known about the best training intensity for this population. The objective was to investigate the impact of an IMT of high intensity, using the critical inspiratory pressure (CIP), on inspiratory muscle strength (IMS), inspiratory muscle endurance (IME), peak power, and oxygen uptake of recreational cyclists; and to compare these results with moderate-intensity IMT (60% of maximal inspiratory pressure [MIP]).

METHODS

Thirty apparently healthy male recreational cyclists, 20-40 years old, underwent 11 weeks of IMT (3 times per week; 55 min per session). Participants were randomized into 3 groups: sham group (6 cmH2O; n = 8); 60% MIP (MIP60; n = 10) and CIP (n = 12). All participants performed the IMS test and incremental IME test at the first, fifth, ninth, and 13th weeks of the experimental protocol. Cardiopulmonary exercise testing was performed on an electromagnetic braking cycle ergometer pre-IMT and post-IMT. Data were analyzed using a 2-way repeated measures ANOVA (group and period factors).

RESULTS

IMS increased in CIP and MIP60 groups at the ninth and 13th weeks compared with the sham group (P < .001; β = 0.99). Regarding IME, there was an interaction between the CIP and MIP60 groups in all periods, except in the initial evaluation (P < .001; β = 1.00). Peak power (in watts) increased after IMT in CIP and MIP60 groups (P = .01; β = 0.67). Absolute oxygen uptake did not increase after IMT (P = .49; β = 0.05). Relative oxygen uptake to lean mass values did not change significantly (P = .48; β = 0.05).

CONCLUSION

High-intensity IMT is beneficial on IMS, IME, and peak power, but does not provide additional gain to moderate intensity in recreational cyclists.

Effects of Submaximal Performances on Critical Speed and Power: Uses of an Arbitrary-Unit Method with Different Protocols

The effects of submaximal performances on critical speed (S_Crit) and critical power (P_Crit) were studied in 3 protocols: a constant-speed protocol (protocol 1), a constant-time protocol (protocol 2) and a constant-distance protocol (protocol 3). The effects of submaximal performances on S_Crit and P_Crit were studied with the results of two theoretical maximal exercises multiplied by coefficients lower or equal to 1 (from 0.8 to 1 for protocol 1; from 0.95 to 1 for protocols 2 and 3): coefficient C₁ for the shortest exercises and C₂ for the longest exercises. Arbitrary units were used for exhaustion times (t_lim), speeds (or power-output in cycling) and distances (or work in cycling). The submaximal-performance effects on S_Crit and P_Crit were computed from two ranges of t_lim (1–4 and 1–7). These effects have been compared for a low-endurance athlete (exponent = 0.8 in the power-law model of Kennelly) and a high-endurance athlete (exponent = 0.95). Unexpectedly, the effects of submaximal performances on S_Crit and P_Crit are lower in protocol 1. For the 3 protocols, the effects of submaximal performances on S_Crit, and P_Crit, are low in many cases and are lower when the range of t_lim is longer. The results of the present theoretical study confirm the possibility of the computation of S_Crit and P_Crit from several submaximal exercises performed in the same session.

Modelling of Running Performances: Comparisons of Power-Law, Hyperbolic, Logarithmic, and Exponential Models in Elite Endurance Runners

Many empirical and descriptive models have been proposed since the beginning of the 20th century. In the present study, the power-law (Kennelly) and logarithmic (Péronnet-Thibault) models were compared with asymptotic models such as 2-parameter hyperbolic models (Hill and Scherrer), 3-parameter hyperbolic model (Morton), and exponential model (Hopkins). These empirical models were compared from the performance of 6 elite endurance runners (P. Nurmi, E. Zatopek, J. Väätäinen, L. Virén, S. Aouita, and H. Gebrselassie) who were world-record holders and/or Olympic winners and/or world or European champions. These elite runners were chosen because they participated several times in international competitions over a large range of distances (1500, 3000, 5000, and 10000 m) and three also participated in a marathon. The parameters of these models were compared and correlated. The less accurate models were the asymptotic 2-parameter hyperbolic models but the most accurate model was the asymptotic 3-parameter hyperbolic model proposed by Morton. The predictions of long-distance performances (maximal running speeds for 30 and 60 min and marathon) by extrapolation of the logarithmic and power-law models were more accurate than the predictions by extrapolation in all the asymptotic models. The overestimations of these long-distance performances by Morton's model were less important than the overestimations by the other asymptotic models.

Gender difference of aerobic contribution to surface performances in finswimming: analysis using the critical velocity method

PURPOSE

Finswimming is a speed competition sport practiced on the surface or underwater, by using monofins or two fins. In surface events (SF), competitors should surface within 15 m after the start and any turns. The aim of this study was to investigate the gender differences in the aerobic contribution to SF performances in finswimming, using the critical velocity (CV) concept in the analysis.

METHODS

The participants were sixteen monofin swimmers (eight males and eight females; 24±6 years). During a two-day period, participants performed maximal effort swimming at five test distances (100 m, 200 m, 400 m, 800 m and 1500 m), and mean swimming velocity (V) of each distance was calculated. CV was calculated as the slope of the regression line between time and distance in the 400 and 800 m SF tests.

RESULTS

Although CV was significantly correlated with V800 m and V1500 m for males, it was significantly correlated with V200 m, V400 m, V800 m and V1500 m for females.

CONCLUSION

The present results suggest that although the aerobic performance might contribute to SF performance for events from medium distance (i.e. 200m) to long distance (i.e. 1500m) in female participants, it might contribute to the long distance SF performances in male participants.

Determining Anaerobic Capacity in Sporting Activities

Anaerobic capacity/anaerobically attributable power is an important parameter for athletic performance, not only for short high-intensity activities but also for breakaway efforts and end spurts during endurance events. Unlike aerobic capacity, anaerobic capacity cannot be easily quantified. The 3 most commonly used methodologies to quantify anaerobic capacity are the maximal accumulated oxygen deficit method, the critical power concept, and the gross efficiency method. This review describes these methods, evaluates if they result in similar estimates of anaerobic capacity, and highlights how anaerobic capacity is used during sporting activities. All 3 methods have their own strengths and weaknesses and result in more or less similar estimates of anaerobic capacity but cannot be used interchangeably. The method of choice depends on the research question or practical goal.

Exercise tolerance in intermittent cycling: application of the critical power concept

PURPOSE

This study tested the relevance of the critical power (CP) model for explaining exercise tolerance during intermittent high-intensity exercise with different recovery intensities.

METHODS

After estimation of CP and W' from a 3-min all-out test, seven male subjects completed, in randomized order, a cycle test to exhaustion at a severe-intensity constant-work-rate (S-CWR) and four cycle tests to exhaustion using different intermittent ("work-recovery") protocols (i.e., severe-severe (S-S), severe-heavy (S-H), severe-moderate (S-M), and severe-light (S-L)).

RESULTS

The tolerable duration of exercise in S-CWR was 384 ± 48 s, and this was increased by 47%, 100%, and 219% for S-H, S-M, and S-L, respectively (all P < 0.05). Consistent with this, compared with S-CWR (22.9 ± 7.4 kJ), the work done above the CP was significantly greater by 46%, 98%, and 220% for S-H, S-M, and S-L, respectively (all P < 0.05). The slope of the relationship between V˙O₂ and time was significantly reduced for S-H, S-M, and S-L (0.09 ± 0.02, 0.09 ± 0.01, and 0.07 ± 0.02 L·min⁻², respectively) compared with S-CWR (0.16 ± 0.03 L·min⁻², P < 0.05). In addition, the slope of the relationship between integrated EMG and time showed a systematic decline for S-H, S-M, and S-L compared with S-CWR (P < 0.05).

CONCLUSIONS

These results indicate that, when recovery intervals during intermittent exercise are performed below the CP, exercise tolerance is improved in proportion to the reconstitution of the finite W'. The enhanced exercise tolerance with the lower-intensity recovery intervals was associated with a blunted increase in both V˙O₂ and integrated EMG with time.

Critical velocity during continuous and intermittent exercises in children

The purpose of this study was to apply the "critical velocity" concept to short intermittent high-intensity running exercises in prepubescent girls and boys and to compare the running performances obtained either by intermittent or continuous exercise runs. Eleven 8 to 11-year-old children underwent a maximal graded field test to determine peak oxygen uptake (peakVO2) and maximal aerobic velocity (MAV). During the six following sessions, they randomly performed three continuous runs (90, 100, and 110% of MAV) and three intermittent runs (120, 130, and 140% of MAV) until exhaustion. Intermittent exercises consisted of repeated 15 s runs each one separated by a 15 s passive recovery interval. For continuous as well as intermittent exercises, distance versus time to exhaustion (TTE) relationships were calculated to determine continuous (CVc) and intermittent (CVi) critical velocities. Values for peakVO2 and MAV were 45.8 +/- 5.3 ml x kg(-1) x min(-1) and 10.5 +/- 1.0 km h(-1), respectively. For the whole population, a significant relationship was found between the distance to exhaustion (DTE) and TTE for continuous (r2= 0.99, P < 0.05) and intermittent exercises (r2 = 0.99, P < 0.05). Significant relationships were found between peakVO2 and both CVc (r2= 0.60, P < 0.01) and CVi (r2= 0.47, P < 0.05). In conclusion, as for continuous exercises, a linear relationship was found between DTE and TTE for short high-intensity intermittent exercises. CVc was significantly related to peakVO2, while a significant lower relationship was found between peakVO2 and CVi.

The critical power and related whole-body bioenergetic models

This paper takes a performance-based approach to review the broad expanse of literature relating to whole-body models of human bioenergetics. It begins with an examination of the critical power model and its assumptions. Although remarkably robust, this model has a number of shortcomings. Attention to these has led to the development of more realistic and more detailed derivatives of the critical power model. The mathematical solutions to and associated behaviour of these models when subjected to imposed "exercise" can be applied as a means of gaining a deeper understanding of the bioenergetics of human exercise performance.

Methods to determine aerobic endurance

Physiological testing of elite athletes requires the correct identification and assessment of sports-specific underlying factors. It is now recognised that performance in long-distance events is determined by maximal oxygen uptake (V(2 max)), energy cost of exercise and the maximal fractional utilisation of V(2 max) in any realised performance or as a corollary a set percentage of V(2 max) that could be endured as long as possible. This later ability is defined as endurance, and more precisely aerobic endurance, since V(2 max) sets the upper limit of aerobic pathway. It should be distinguished from endurance ability or endurance performance, which are synonymous with performance in long-distance events. The present review examines methods available in the literature to assess aerobic endurance. They are numerous and can be classified into two categories, namely direct and indirect methods. Direct methods bring together all indices that allow either a complete or a partial representation of the power-duration relationship, while indirect methods revolve around the determination of the so-called anaerobic threshold (AT). With regard to direct methods, performance in a series of tests provides a more complete and presumably more valid description of the power-duration relationship than performance in a single test, even if both approaches are well correlated with each other. However, the question remains open to determine which systems model should be employed among the several available in the literature, and how to use them in the prescription of training intensities. As for indirect methods, there is quantitative accumulation of data supporting the utilisation of the AT to assess aerobic endurance and to prescribe training intensities. However, it appears that: there is no unique intensity corresponding to the AT, since criteria available in the literature provide inconsistent results; and the non-invasive determination of the AT using ventilatory and heart rate data instead of blood lactate concentration ([La(-)](b)) is not valid. Added to the fact that the AT may not represent the optimal training intensity for elite athletes, it raises doubt on the usefulness of this theory without questioning, however, the usefulness of the whole [La(-)](b)-power curve to assess aerobic endurance and predict performance in long-distance events.