Publication: used Physiology, Nutrition, and also Metabolism • 16 in march 2020 •
Mechanical adaptations that skinned cardiac muscle in solution to dietary-induced obesity during adolescence in rats
Inclusion of mrs participants in cardiovascular research: a situation study the Ontario NSERC-funded programs

We experiment the theory that revolution stretching, one acute, nonmetabolic fatiguing intervention, reduces practice tolerance by enhancing muscle activation and also affecting muscle bioenergetics throughout cycling in the “severe” soot domain. Ten active men (age, 24 ± 2 years; body mass, 74 ± 11 kg; height, 176 ± 8 cm) participated in identical constant-load cycling exam of equal intensity, of i m sorry 2 tests were lugged out under regulate conditions and also 2 were done after stretching. This brought about a 5% reduction of maximal isokinetic sprinting power output. Us measured (i) oxygen consumption, (ii) electromyography, (iii) deoxyhemoglobin, (iv) blood lactate concentration; (v) time to exhaustion, and (vi) perception of effort. Finally, oxygen consumption and also deoxyhemoglobin kinetics were determined. Force reduction complying with stretching was accompanied through augmented muscle excitation at a provided workload (p = 0.025) and a far-ranging reduction with time to fatigue (p = 0.002). The time to optimal oxygen usage was decreased by extending (p = 0.034), suggesting an affect of the enhanced muscle excitation top top the oxygen consumption kinetics. Moreover, stretching was associated with a mismatch in between O2 delivery and utilization during the isokinetic exercise, boosted perception of effort, and blood lactate concentration; these observations are all consistent with an increased contribution of the glycolytic energy system to sustain the very same absolute intensity. This results suggest a link in between exercise intolerance and also the decreased ability to create force.

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We noted the first characterization the the results of prolonged stretching top top the metabolic an answer during significant cycling.
Stretching reduced maximal force and augmented muscle activation, which consequently increased the metabolic solution to sustain exercise.
Nous testons l’hypothèse selon laquelle l’étirement statique, qui est une treatment ponctuelle fatigante mais no métabolique, réduit la tolérance à l’exercice en augmentant l’activation musculaire et en influant sur la bioénergétique musculaire au cours d’un exercice de pédalage dans le domaine d’intensité « sévère ». Dix hommes actifs (24 ± 2 ans, 74 ± 11 kg, 176 ± 8 cm) participent à des tests de pédalage à intensité constante identique dont deux sont effectués dans des conditions de contrôle et deux après l’étirement, ce qui suscite une réduction de 5 % de la puissance maximale de acceleration isocinétique. Nous mesurons : (i) la consommation d’oxygène, (ii) l’électromyogramme, (iii) la désoxyhémoglobine, (iv) la concentration sanguine de lactate, (v) le délai d’épuisement et (vi) la perception de l’effort. Enfin, la cinétique de la consommation d’oxygène et de la désoxyhémoglobine est évaluée. La réduction de la pressure après l’étirement est accompagnée d’une activation musculaire accrue à une charge de travail donnée (p = 0,025) et d’une réduction significative de délai d’épuisement (p = 0,002). Le délai jusqu’au pic de la consommation d’oxygène est réduit par l’étirement (p = 0,034), ce qui suggère une influence de l’augmentation de l’activation musculaire sur la cinétique de la consommation d’oxygène. De plus, l’étirement est associé à un décalage entre la livraison et l’utilisation d’O2 pendant l’exercice isocinétique, à un accroissement de la late de l’effort et de la concentration sanguine de lactate; ces observations sont toutes compatibles avec une contribution accrue du système d’énergie glycolytique pour maintenir la même intensité absolue. Ces résultats suggèrent un lien entre l’intolérance à l’exercice et la diminution de la capacité à produire de la force.
Nous présentons la première caractérisation des effets d’un étirement prolongé sur la réponse métabolique lors de séances sévères de pédalage.
L’étirement a réduit la pressure maximale et augmenté l’activation musculaire, ce qui a augmenté la réponse métabolique pour soutenir l’exercice.
During whole-body practice at constant-load in the moderate domain, oxygen consumption (V̇O2) adapts to the energetic requirements of locomotor and ventilatory muscles within 3 min (Poole and also Jones 2012). If family member intensity rises over the gas exchange threshold (GET), roughly after the third minute of practice V̇O2 displays a “slow component” (V̇O2sc) that is commonly interpreted together an increased price of locomotion for a provided exercise intensity (Poole and Jones 2012). In particular, as soon as exercise is performed between the metabolic rates linked with the GET and the respiratory tract compensation allude (RCP; i.e., hefty intensity domain) (Keir et al. 2015, 2018), V̇O2sc has tendency to a steady-state; however, when initiative rises above the RCP (i.e., significant exercise domain) a steady-state is no longer achievable and V̇O2 rises towards maximum oxygen intake (V̇O2max) (Jones et al. 2011). The size of V̇O2sc is considered connected with exercise intolerance and also fatigue (Grassi et al. 2015). Therefore, during the past 40 years numerous researchers have concentrated their attention on clarifying the physiological bases that V̇O2sc (Jones et al. 2011). Two main theories have been propose to explain the physiological beginning of V̇O2sc: (i) decreased metabolic security of form I muscle fibres linked with increased O2 price of adenosine triphosphate (ATP) resynthesis and/or increased ATP cost of contraction (Jones et al. 2011; Grassi et al. 2015); and also (ii) recruitment of fast-fatigable fundamentally inefficient kind II muscle fibres come obtain/maintain the exterior power calculation (PO) over a specific intensity threshold (e.g., RCP) (Jones et al. 2011; Poole and Jones 2012; Grassi et al. 2015). However, the precise physiological mechanisms underpinning V̇O2sc continue to be elusive, among the factors being the an obstacle to selectively impact either metabolic security or type II fibre recruitment in human models. In fact, the different manipulations supplied in interventional research studies (e.g., rate of movement, strongness modulation, aerobic training, priming exercise, nutritional interventions) impact to some extent both metabolic stability and fibre recruitment (Jones et al. 2011).
An interesting approach to selectively augment fibre recruitment while trying to prevent the perturbation of metabolic stability is acute, nonmetabolic tiredness that to reduce the ability of muscle to develop force. Among the interventions may be to cause acute nonmetabolic fatigue, a promise model can be static stretching, which deserve to impair force production as result of prolonged nervous stimulation (Trajano et al. 2017). The was extensively documented the stretching, an especially when location are maintained for an ext than 60 s, deserve to impair maximal pressure in plenty of different tasks and conditions for a duration lasting as much as 1 h (Behm et al. 2016). Offered that no effort is forced to do stretching, and that force special needs after extending is largely caused by neural instrument (Trajano et al. 2017), this would certainly be a specifically convenient design to acutely reduce force and also investigate the link between muscle activity and metabolism. Indeed, current studies (Esposito et al. 2012) documented that when maximal force was acutely reduced by stretching, the oxygen cost of locomotion increases both during ramp incremental (exercise modality in i m sorry the V̇O2sc is characterized as “excess V̇O2” (Grassi et al. 2015)) and constant-load practice (Esposito et al. 2012; Limonta et al. 2015). However, the above studies walk not especially investigate the underpinnings that V̇O2sc and also were, therefore, lacking measures to inspection the link in between muscle activation and increased V̇O2 (e.g., electromyography (EMG)). In a current study from our group, the effects of extending on the V̇O2 response during ramp incremental cycle were explained while additionally implementing actions of muscle excitation (Colosio et al. 2019). We discovered that once muscle force is acutely impaired by extending muscle excitation additionally increases in unison through an increased cost of locomotion (i.e., V̇O2 at a provided absolute workload).
The above findings, in an incremental practice paradigm, assistance the presence of a succession of occasions (i.e., acute fatigue, boosted muscle activation, ns of metabolic efficiency) that causes the V̇O2sc with increasing exercise intensity. In this context, constant-load exercise represents the ideal model to recognize the feasible role of enhanced muscular activation in time (necessary to keep the same workload as soon as fatigued) in the genesis that the V̇O2sc. In fact, only under prolonged, constant-load conditions, the increased price of locomotion (i.e., V̇O2sc) at a provided intensity has the time to totally manifest itself. The check of a connection in between fatigue/increased muscle activation and the ns of metabolic performance over time during a constant-load practice paradigm would additional support the presence of a causative link.
Accordingly, this examine investigated the impacts of acute, nonmetabolic fatigue induced by stretching on central and peripheral physiological steps (V̇O2, blood lactate concentration , electromyography (EMG), Near-Infrared Spectroscopy (NIRS)) throughout constant-load to ride bicycle in the major exercise domain. We hypothesized that extending (i) would mitigate maximal muscle force; (ii) in turn, force loss would analyze in enhanced muscle excitation at a offered absolute workload and (iii) boosted muscle excitation would alleviate exercise tolerance and increase the V̇O2 price of locomotion. Finally, this study will administer the an initial comprehensive investigation on the effects of static extending on high-intensity constant-load cycling.
Ten energetic men provided written informed consent to participate in the study (age: 24 ± 2 years, human body mass: 74 ± 11 kg, stature: 176 ± 8 cm). Inclusion criteria were male sex and age between 20 and 35 years; exclusion criteria were smoking and also any problem that might influence the physiological responses throughout testing. The research was approved by Departmental principles Committee and also adhered come the values of the explanation of Helsinki. All participants were instructed to prevent physical activity for at least 24 h prior to each experimentation session and followed a standard and individualized food intake prescription before all the testing sessions to minimization variability that glycogen stores and also glucose oxidation (i.e., 2 g of low glycemic index carbohydrates every kg of human body weight, 2 h before testing; 0.5 l of water in the 90 min before testing; restriction indigenous caffeine throughout the 8 h prior to testing).
After clinical clearance, participants checked out the activities on 8 occasions in ~ a maximum of 3 weeks.
On the an initial 2 visits, subjects familiarized through a test consisting that isokinetic sprints for the determination of the maximal cycling PO. ~ above the 3rd appointment, isokinetic sprints to be performed before and after either the control condition (i.e., 40 min of seated rest, control) or 40 min of extending to determine the result of extending on the maximal cycle PO. Top top the fourth visit, subjects performed a ramp incremental test to fatigue for the decision of the GET, the RCP, and also the V̇O2max. Then, throughout the last 4 visits participants repetitive 4 similar constant-load trials in the major exercise soot domain (at a PO equivalent to Δ60% in between GET and also V̇O2max). Randomly, 2 the the constant-load trials were lugged out in control conditions and also 2 the the constant-load trials were excellent after 40 min of stretching. A schematic representation of the protocol is detailed in Fig. 1.
Fig. 1. Schematic representation of the overall protocol (above), and of the single testing sessions (below). GET, gas exchange threshold; PO, power output; V̇O2, oxygen consumption; V̇O2max, maximal oxygen consumption.
All the the test were performed at the very same time the the day in an environmentally managed laboratory (22–25 °C, 55%–65% relative humidity) on an electromagnetically braked bike ergometer (Sport Excalibur; Lode, Groningen, Netherlands). Ergometer position was chosen throughout the an initial familiarization visit and recorded for the succeeding appointments.
Six cycles of extending were offered to maximize acute force reduction (Behm et al. 2016). The standardized extending cycle sequentially connected (i) the quadriceps of the right leg, (ii) the appropriate hamstrings, (iii) the left quadriceps, and also (iv) the left hamstrings. Each position was kept for 80 s v no recovery between positions. Subjects were continuously motivated to stretch muscle to the allude of discomfort. The full duration of the stretching intervention was around 40 min. Stretching efficiency in increasing flexibility was measure up before and after stretching and also control making use of a sit-and-reach test (Limonta et al. 2015).
To assess pressure reduction after ~ stretching, isokinetic maximal sprints were performed on an electromagnetically braked cycle-ergometer in isokinetic setting equipped with a pedal pressure sensor (Sport Excalibur PFM; Lode) as previously defined (Colosio et al. 2019). In brief, 2 pedalling frequencies (60 and also 120 rpm) were provided to measure up velocity-specific optimal power together proposed through Cannon et al. (2011). Each sprint session consisted of four 5-s maximal sprints, alternate between 60–120–60–120 rpm. The 4 maximal sprints were separated by a 2-min passive remainder to maximise restore while limiting the complete duration the the sprint session.
The ramp incremental test contained 4-min the baseline cycling at 20 W, complied with by rises in PO varying from 17.5 to 25 W/min according to individuals’ predicted fitness level with the target of obtaining a time to fatigue (TTE) the ∼8–12 min (American college of Sports medicine 2017) utilizing a an approach extensively explained elsewhere (Pogliaghi et al. 2014). Participants to be asked to choose a self-selected cadence in the variety of 70–90 rpm and to keep it throughout all tests. Fail to keep the suggested cadence in ~ 5 rpm (for longer than 5 s) during testing despite strong verbal encouragement was taken into consideration as the criterion because that exhaustion. Breath-by-breath pulmonary gas exchange, ventilation, and heart rate were continuously measured utilizing a metabolic dare (Quark B2; Cosmed, Italy) as previously explained (De Roia et al. 2012).
After the preliminary ramp incremental test, topics completed 4 constant-load trials at the PO corresponding to the 60%Δ in between GET and V̇O2max. 2 of the constant-load trials were performed ~ stretching and also 2 the the constant-load trials were brought out after manage in a randomized order. In each condition, 1 constant-load trial lasted 10 min if the various other was carry out to exhaustion to allow recording that TTE after control and also stretching. Constant-load trials were came before by a 4-min warm-up in ~ 20 W in i beg your pardon cycling cadence was minimal to 30 rpm come minimize any type of metabolic activation that could influence the effects of stretching and the physiological response at the beginning of exercise. Throughout the test, subjects maintained the same constant rpm selected throughout the ramp incremental test and the very same bike position selected during the acceleration test.
Surface EMG of the right vastus lateralis and also biceps femoris muscles were continuously taped by method of a wireless mechanism (Wave wireless EMG; Cometa, Milan, Italy). A pair of surface Ag/AgCl electrodes (Blue sensor, Ambu, Ballerup, Denmark) was attached come the skin through a 2-cm inter-electrode distance. The electrodes were inserted longitudinally with respect come the basic muscle fibres arrangement, according to the referrals by surface ar EMG for Non-Invasive assessment of muscles (Hermens et al. 2000). Prior to electrode application, the skin to be shaved, scratched with sandpaper, and cleaned with alcohol to minimize impedance. Semi-permanent octopus marks enabled consistent re-positioning of the electrodes between sessions. The EMG transmitter linked to the electrodes was well secured with adhesive ice to protect against movement-induced artifacts.
V̇O2, ventilation (V̇E), respiratory exchange ratio, and heart rate data to be measured with the same technique described because that the ramp incremental test. During each constant-load trial, capillary blood samples (20 μL) were drawn from the earlobe in the last 30 s the warm-up, during the first, third, fifth, seventh, and also tenth minutes, and also then every 5 min the the trial come exhaustion. Moreover, blood samples were drawn at the first, third, fifth, and seventh minute after exhaustion. Samples were immediately analyzed to measure up (Biosen C-Line; EKF Diagnostics, Barleben, Germany).
Deoxygenation that the left vastus lateralis was evaluated in microcirculation using a quantitative NIRS (Oxiplex TSTM; ISS, Champaign, Ill., USA) the provided constant measurement (sampling frequency 1 Hz) of the pure concentrations (μmol/L) the deoxyhemoglobin concentration (). After ~ shaving, cleaning, and also drying of the skin area, the NIRS probe was positioned longitudinally on the belly of the vastus lateralis muscle at ∼15 cm above the patella, attached come the skin with a bi-adhesive tape, and secured with elastic bandages approximately the thigh. The maker was calibrated before each check after a warm-up of at the very least 30 min together per manufacturer recommendations.
Finally, perceptual responses to exercise was monitored using a 0–100 rating of regarded exertion (RPE) range (Borg and Kaijser 2006). The range was displayed to the participants throughout baseline, every 5 min during the constant-load trials, and also immediately after ~ exhaustion.
Crank torque was measured individually from the 2 crank eight by stress, overload gauge transducers (maximal recordable pressure 2000 N, Ramp incremental test
For the gas exchange variables, aberrant data-points the lay 3 SD indigenous the local mean to be removed, and trials were linearly interpolated top top a 1-s basis and also then averaged every 5 s. V̇O2max was determined as the greatest V̇O2 obtained over a 10-s term (Fontana et al. 2015). GET and RCP were figured out with the standard method from gas exchange variables by 3 blinded skilled reviewers as comprehensive elsewhere (Fontana et al. 2015). Briefly, obtain was identified by intuitive inspection as the V̇O2 at which CO2 output started to boost out of proportion in relationship to V̇O2, with a systematic climb in the V̇E-to-V̇O2 relation and end-tidal PO2 vice versa, the ventilatory tantamount of carbon dioxide manufacturing (V̇CO2) (V̇E/V̇CO2) and end-tidal PCO2 is steady (Beaver et al. 1986). RCP was determined as the allude where end-tidal PCO2 started to autumn after a period of isocapnic buffering (Whipp et al. 1989). This allude was shown by examining V̇E/V̇CO2 plotted versus V̇O2 and by identify the 2nd breakpoint in the V̇E-to-V̇O2 relation. V̇O2max was determined as the highest V̇O2 obtained over a 10-s interval. Finally, we identified the continuous workload identical to the certain severe (60%Δ between GET and V̇O2max) V̇O2 target. Come this aim, the V̇O2/W relationship established with the incremental test to be left-shifted come account because that the individual mean solution time. Briefly, the mean response time was figured out as the time interval between the onset of the incremental portion of the practice (time = 0) and the increase of the V̇O2 signal over baseline. It was identified as the x coordinate of the intersection of the forward extrapolation the the baseline V̇O2 and also the backwards extrapolation of the direct V̇O2–time relationship below the get (Fontana et al. 2015).
The life EMG signal was rectified and smoothed making use of a fourth-order band-pass Butterworth digital filter through a frequency range set between 20 and also 500 Hz. Root average square (RMS) to be calculated every second and average at 30-s intervals indigenous the raw signal and also was used as an index of the complete muscle excitation for vastus lateralis (RMSVL) and biceps femoris (RMSBF) (Vigotsky et al. 2018). Thereafter, the RMS recorded throughout the critical 2 min the 20 W baseline for each test was offered to normalize the constant-load trials and expressed together multiples of baseline.
V̇O2 throughout constant-load trials was cleaned and interpolated utilizing the very same procedure explained for the ramp incremental test. Then, data that the 2 constant-load trials perform in each problem were mediated to reduce breath-by-breath signals variability. Finally, 30-s way were calculated.
Net accumulation during constant-load trials to be calculated as the difference between in ~ a particular timepoint and also the throughout cycling at 20 W. The greatest value after ~ exercise finish was considered as the peak of .
NIRS-derived solution during constant-load trials to be time aligned v the beginning of practice transition, cure by subtracting the steady-state value measured throughout the critical 2 min that warm-up, and then average at 30-s bins.
Using 1-s bins data, the on-transient responses to practice of V̇O2 to be modelled as follows: first, the V̇O2 response from −60 up to 180 s (time 0 being exercise onset) was preliminarily defined with a 2-component version (linear + exponential), combined by a Heaviside function, ~ the exclusion of the data clues of the early 20 s of exercise that coincided to the cardiodynamic phase (Murias et al. 2011a). With this approach, we obtained the early parameters for the major component. Then, the complete on-transient responses to practice of V̇O2 were modelled indigenous the onset of workload to the end of the tenth minute (or to fatigue for tests the lasted less than 10 min after ~ stretching) using the adhering to 2-component exponential equation incorporated by a Heaviside role (De Roia et al. 2012):

where Y(t) represents the rise in V̇O2 in ~ the beginning of exercise; Yblsn is the baseline V̇O2 worth recorder throughout the 4 min that 20 W cycling; AMPp and AMPsc represent the amplitude of the V̇O2 response above the baseline value of the primary and the sluggish component, respectively; and τp, τsc, TDp, and TDsc room the time consistent and the time delay of the solution for every component, respectively. The mean solution time (MRT) was then calculated as the sum of τ + TD. Furthermore, us calculated the time requested to with V̇O2max throughout constant-load trials by fixing on the individual installation of V̇O2 data for the moment coordinate corresponding to V̇O2max.
signal to be fitted ~ above a time window of −60 to 180 s (time 0 being exercise onset) utilizing a 2-component model (linear + exponential), combined by a Heaviside function, as previously described (De Roia et al. 2012).
Finally, and also V̇O2 data to be normalized with 0% corresponding to the value tape-recorded while cycling in ~ 20 W baseline and 100% showing the maximal an answer in the 180-s home window and expressed together Δ and also ΔV̇O2. Individualized 1-s Δ and ΔV̇O2 to be time-aligned by left-shifting the V̇O2 data through 20 s (i.e., the usual duration that the cardiodynamic step in young people (Murias et al. 2011b). Then, the ratio in between Δ/ΔV̇O2 was calculated throughout the first 180 s of practice to to express the fountain muscle O2 extraction forced to sustain a offered net increment the V̇O2 (De Roia et al. 2012). Finally, the adhering to indexes to be calculated: Δ/ΔV̇O2 area under the curve (AUC), together the integral the the total mismatch in between O2 delivery and utilization (i.e., index worths > 1); Δ/ΔV̇O2 peak, together the maximal value reached within the 180 s; Δ/ΔV̇O2 time to peak, together the time asked for to with the optimal in Δ/ΔV̇O2. Moreover, offered that these time-resolved values are typically implemented during steady-state condition, an as whole quantification that the boost in fractional muscle O2 extraction forced to sustain a offered net increment in V̇O2 during the main phase of exercise was calculated by splitting the amplitudes that the response in V̇O2 and in between the start of exercise and the onset of the slow component: overall Δ/ΔV̇O2 (Tam et al. 2018).
After presumptions verification (i.e., normality, homogeneity that variance), 2-way repeated-measures ANOVA was applied to compare flexibility values (pre– and post–sit-and-reach ~ control/stretching). Pre- and post-peak POs measured throughout isokinetic sprints at 60 and also 120 rpm were contrasted pre- and also post-stretching, utilizing a 2-way repeated-measures ANOVA (time × pedalling frequency).
For constant-load trials, 2-way repeated-measures ANOVAs were performed to compare V̇O2, net , RPE, , RMSVL, and RMSBF in between conditions in time (time × condition). Article hoc analyses were performed making use of the Holm–Sidak test. Student’s t test was used to compare in between conditions the TTE, parameters that V̇O2 and also kinetics (τ, TD, and also MRT), time come V̇O2max, Δ/ΔV̇O2 AUC, Δ/ΔV̇O2 peak, Δ/ΔV̇O2 time come peak, and overall Δ/ΔV̇O2.
Data are presented as way ± SD. α was set in breakthrough at the 0.05 level and significance was welcomed when ns p and also TDsc, τp, and also τsc the V̇O2 kinetics, and also of TD and τ the kinetics to be calculated based upon the asymptotic intervals the the nonlinear parameters resulting from the fitting (Field et al. 2012). Impact sizes of the differences between control and stretching were likewise reported (Cohen’s d, ranked as trivial (0–0.19), little (0.20–0.49), tool (0.50–0.79), and large (≥0.80)) together objective and also standardized procedures to quantifying the magnitude of distinction after stretching versus regulate (Cumming 2014). In Cohen’s effect size calculation, the SD in the control condition was used to standardize the mean difference for each contrast (Field et al. 2012). Moreover, generalized eta squared (ηG2) were calculated to quantify the results sizes of different independent variables during the constant-load trials (Olejnik and Algina 2003; Bakeman 2005). Based on an supposed SD of breath-by-breath V̇O2 measurements for steady-state exercise equal come 2.5%, and a minimum detectable change in V̇O2 of 100–170 mL/min in ~ a V̇O2 that 2.1 come 3.5 L/min (Keir et al. 2015), the minimum sample size to attain a power of 0.8 to be 6 individuals. All statistical analyses were performed using SigmaPlot, version 12 (Systat software application Inc, USA).

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Flexibility, as measured by sit-and-reach test, to be not substantially different in ~ baseline in between stretching and also control and significantly enhanced only after stretching (pre-stretching: +0.3 ± 6.5 centimeter vs post-stretching: +6.1 ± 5.9 cm, p d = +0.89; pre-control: +0.7 ± 5.1 cm vs post-control: +0.8 ± 4.9 cm, ns = 0.784, d = +0.02). The top PO measured throughout isokinetic sprints pre-stretching was lessened after the intervention by ≈ 5% (Table 1). ANOVA revealed a far-reaching main effect of time (p ≤ 0.001) and also pedalling frequency (p ≤ 0.001), through no interaction (p = 0.885). Short article hoc analysis confirmed that peak PO was significantly reduced by extending both during the 60 rpm and also the 120 rpm sprints (Table 1).