© 2014 John Wiley & Sons A/S.

Scand J Med Sci Sports 2014: ••: ••–•• doi: 10.1111/sms.12298

Published by John Wiley & Sons Ltd

Effects of acute and 2-week administration of oral salbutamol on exercise performance and muscle strength in athletes M. Hostrup1,2, A. Kalsen1,2, M. Auchenberg1, J. Bangsbo1, V. Backer2 1

Department of Nutrition, Exercise & Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark, Respiratory Research Unit, Bispebjerg University Hospital, Copenhagen, Denmark Corresponding author: Morten Hostrup, Department of Nutrition, Exercise & Sports, Section of Integrated Physiology, University of Copenhagen, Respiratory Research Unit, Bispebjerg University Hospital, Bispebjerg Bakke 23, Bygning 66, DK-2400 Copenhagen NV, Denmark. Tel: +45 2447 4785, Fax: +45 3531 2179, E-mail: [email protected] 2

Accepted for publication 24 June 2014

Our objective was to investigate effects of acute and 2-week administration of oral salbutamol on repeated sprint ability, exercise performance, and muscle strength in elite endurance athletes. Twenty male elite athletes [VO2max: 69.4 ± 1.8 (Mean ± SE) mL/min/kg], aged 25.9 ± 1.4 years, were included in a randomized, doubleblinded and placebo-controlled parallel study. At baseline, after acute administration, and again after 2-week administration of the study drugs (8 mg salbutamol or placebo), subjects’ maximal voluntary contraction (MVC) of m. quadriceps and isometric endurance of m. deltoideus were measured, followed by three repeated Wingate tests. Exercise performance at 110% of VO2max

was determined on a bike ergometer. Acute administration of salbutamol increased peak power during first Wingate test by 4.1 ± 1.7% (P < 0.05). Two-week administration of salbutamol increased (P < 0.05) peak power during first and second Wingate test by 6.4 ± 2.0 and 4.2 ± 1.0%. Neither acute nor 2-week administration of salbutamol had any effect on MVC, exercise performance at 110% of VO2max or on isometric endurance. No differences were observed in the placebo group. In conclusion, salbutamol benefits athletes’ sprint ability. Thus, the present study supports the restriction of oral salbutamol in competitive sports.

In competitive sports, the use of beta2-agonists is common because of the high prevalence of asthma and exercise-induced bronchoconstriction (EIB) among elite athletes (McKenzie & Fitch, 2011). The high use of beta2-agonists, especially among endurance athletes, has lead to anecdotic evidence that these agents increase performance, although most scientific literature report no enhancing effects of inhaled beta2-agonists on performance when taken by non-asthmatic athletes (Carlsen et al., 2008; Wolfarth et al., 2010; Pluim et al., 2011). In 2010, World Anti-doping Agency (WADA) loosened their restrictions toward the common beta2-agonists, salbutamol and salmeterol, followed by a loosening in 2012 for the long-acting beta2-agonist, formoterol. Hence, these agents are allowed by inhalation in therapeutic doses by athletes in treatment of asthma and EIB (www.wada-ama.org). Although, oral beta2-agonists still are banned, in and out of competition, pharmacokinetic data indicates that 50% of urine samples collected 12 h following administration of oral salbutamol are false negative making the window to detect oral misuse of salbutamol limited in doping analysis (Hostrup et al., 2014). While inhaled beta2-agonists seem to be without any relevant effects on performance when used in therapeutic

doses, acute administration of oral salbutamol has been observed to increase peak power and mean power during a Wingate test (Collomp et al., 2005; Le Panse et al., 2007). Furthermore, oral salbutamol may increase isokinetic muscle strength (van Baak et al., 2000) in recreational subjects. In addition, short-term administration of beta2-agonists has been reported to be anabolic in animal models, and increases peak power and muscle strength in humans (Martineau et al., 1992; Caruso et al., 1995; Zhang et al., 1996; Le Panse et al., 2005; Sanchez et al., 2012). Most studies providing evidence of improved performance after administration of oral salbutamol have, however, been conducted in recreational subjects, and are therefore not representative of elite athletes (Pluim et al., 2011). In cycling, most Olympic endurance events are decided at intensities above 85% of maximal oxygen uptake (VO2max), which require athletes to have a large anaerobic metabolism and to be fatigue resilient (Joyner & Coyle, 2008). In addition, intensity may shift during a stage, making cyclists’ ability to work intermittently at a high intensity important, for instance during a final sprint or during a climb (Atkinson et al., 2003). It has yet to be established whether oral beta2agonists increase repeated sprint ability and intermittent supramaximal exercise performance, as former studies

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Hostrup et al. have focused on single test protocols. Clearly, these issues need to be clarified to understand the effects of beta2agonists in elite athletes in relation to high-intensity performance. Therefore, our objective was to investigate acute and short-term effects of oral salbutamol on repeated sprint ability, intermittent high-intensity exercise performance, and muscle strength in endurance athletes. Methods Subjects and ethics approval Twenty endurance male athletes competitive in cycling (n = 6), mountain biking (n = 7), and triathlon (n = 7) took part in the study. Subjects were competitive at highest national level of their class. Included subjects had a weekly training volume of 14.9 ± 1.0 h/week and a VO2max of 69.4 ± 1.8 mL/min/kg. Subjects had no history of asthma or airway symptoms and had never used anti-asthmatic medication such as beta2-agonists. Subjects received oral and written information about the aims and contents of the study and possible risks involved. Before the start of the study, subjects gave their written informed consent. Included subjects attested to refrain from competitive events for the entire study and for at least 14 days after the last study visit. The study was performed in accordance with the Helsinki II declaration and was approved by the local ethics committee of Copenhagen (H-12010-105) and by the Danish Health and Medicines Authority (EudraCT: 2010-024339-18). Furthermore, the study was conducted in collaboration with the Good Clinical Practice-Unit of Copenhagen who monitored the study.

Experimental design The study was double-blinded, randomized, and placebocontrolled with parallel design. Before the start of the intervention, subjects’ VO2max and performance were determined in an incremental exercise test to exhaustion on a bike ergometer (Monark 839E, Monark Exercise AB, Vansbro, Sweden). Before the incremental test and after exhaustion, forced expired volume in 1 s (FEV1) was measured repeatedly for 30 min. A drop in postexercise FEV1 by more than 10% compared with baseline FEV1 was considered a positive test for EIB, and an exclusion criterion. Following FEV1 measurements, subjects completed familiarization to performance tests used in the intervention. Two further familiarization visits were completed. After screening and familiarization, subjects were randomly assigned to either a salbutamol group (SAL) (n = 10) or a placebo group (PLA) (n = 10). There were no differences in subject characteristics between the groups (Table 1). Following randomization, subjects completed two baseline visits (Abaseline and Bbaseline)

that served as control visits for the intervention. At visit A, subjects reported to the laboratory and had a catheter inserted in the antecubital vein for blood sampling. Then subjects warmed up for 15 min on a bike ergometer at 150W after which maximal inspiratory and expiratory mouth pressures (MIP/MEP) were measured. Two minutes following MIP/MEP, subjects performed an exercise performance test on a bike ergometer at an intensity corresponding to 110% of VO2max consisting of two 2 min bouts and a final bout to exhaustion, each interspersed by 2 min of recovery. Venous blood samples were drawn from the antecubital vein before (pre) and immediately after each bout (EX1, EX2, and EX3), and up until 15 min post-last bout. Blood samples were immediately analyzed on an ABL 800 Flex (Radiometer Medical, Brønshøj, Denmark) for concentrations of lactate, glucose, and K+. At visit B, subjects reported to the laboratory and had a catheter inserted in the antecubital vein for blood sampling. Then subjects warmed up for 15 min on a bike ergometer at 150W. Two minutes after warm-up, subjects performed three to four maximal voluntary isometric contractions (MVC) of m. quadriceps, followed by an isometric endurance test of m. deltoideus to exhaustion. Hereafter, subjects performed three short sprints of 3–4 s on a bike ergometer. After 4 min of recovery, subjects completed three repeated 30 s Wingate tests each interspersed by 2 min of recovery. Venous blood samples were drawn from the antecubital vein before (pre) and immediately after each bout (W1, W2, and W3), and up until 15 min post-last bout. Blood samples were immediately analyzed on an ABL 800 Flex for lactate, glucose, and K+. At least 2 days after baseline visit B, subjects started the intervention. The intervention consisted of four visits: two visits (Aacute and Bacute) measuring effects of acute administration of study drugs and two visits (Atwo-week and Btwo-week) measuring short-term effects following 14 ± 1 (Atwo-week) and 16 ± 1 (Btwo-week) days of daily intake of study drugs. Intervention visit A and B were similar to baseline visit A and B. During the intervention, subjects kept their regular training regimen that did not change during the intervention. Subjects’ regular training regimen did mainly consist of moderate intensity aerobic exercise and did not include any specific sprint or resistance training. Subjects had a follow-up visit 1 ± 3 day after the intervention, where they reported any side effects and had their body mass and VO2max measured as prior to the intervention. On days of testing, subjects reported to laboratory at least 2 h after consuming a standardized light meal. Subjects were instructed to standardize food and fluid intake before each visit to the laboratory, refrain from strenuous physical activity 48 h before testing, and abstain from alcohol and caffeine consumption 24 h before testing. In an attempt to standardize circumstances of testing, subjects were asked to consider each visit as a competitive event and prepare accordingly. Testing was conducted in the same conditions (temperature and humidity) and with a fan behind subjects for cooling. In the study period, the same bike ergometer (Monark E839) was used. The ergometer was calibrated prior to all tests. Subjects used the same geometric setup, as well as their own pedals and shoes during the tests.

Table 1. Subject characteristics of SAL and PLA

Age (years) Height (cm) Weight (kg) VO2max (mL/min/kg) iPPO (W) Training volume (h/week)

SAL (n = 10)

PLA (n = 10)

25.1 ± 1.6 186 ± 2 75.1 ± 1.6 69.5 ± 1.9 449 ± 9 14.6 ± 1.0

26.6 ± 1.3 180 ± 2 72.8 ± 2.0 69.3 ± 1.8 432 ± 9 15.1 ± 1.0

Mean ± standard error of the mean. iPPO, incremental peak power output; PLA, placebo; SAL, salbutamol; VO2max, maximal oxygen uptake.

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Study medication Upon arrival to the laboratory, study drugs, 8 mg salbutamol (Ventoline®, GlaxoSmithKline, Brentford, UK) or placebo were orally administered 2 h before first test, as this is the time in which systemic concentrations of oral salbutamol reach their peak (Elers et al., 2010, 2012a; Hostrup et al., 2014). Study drugs were produced, packed, and randomized by the Hospital Pharmacy of RegionH (Copenhagen, Denmark) in accordance with Good Manufacturing Practice. To optimize blinding, study drugs were produced in gelatin capsules with same color. To simulate real-life drug administration, subjects were instructed to ingest study drugs 2 h before each training session during the intervention. On days

Role of salbutamol on performance in athletes with no training, subjects were instructed to ingest study drugs at the same time of the day as on training days. Following the intervention and data analysis, randomization was confirmed by serum samples analyzed for salbutamol by the WADA-accredited Norwegian Doping Control Laboratory in Olso, Norway (Hostrup et al., 2014).

Experimental procedures Maximal oxygen uptake After a 10 min warm-up at 100 W, the incremental test started at 150 W with a step-wise increase of 25 W every 1 min until exhaustion. After the test, incremental peak power output (iPPO) was calculated as sum of power output (W) at last step and duration at last step divided by 60 s × 25 W. Subjects’ iPPO are presented in Table 1. VO2max was measured during the incremental test by a breath-by-breath gas analyzing system (JAEGER MasterScreen CPX; Viasys Healthcare GmbH, Höechberg, Germany). During the test, subjects were told to keep a cadence between 80 and 90 rpm. Time to fatigue was defined as the point where pedaling frequency fell below 70 rpm for more than 5 s despite strong verbal encouragement. Before start of the test, the gas analyzing system was calibrated with two gases of known O2 and CO2 concentrations, as well as with a 3–l syringe for tube flow meter calibration. VO2max was defined as the highest value recorded in any 30 s period before cessation of exercise. A plateau in the oxygen uptake despite an increased power output and a respiratory exchange ratio above 1.15 were used as criteria for VO2max achievement. Lung function and maximal inspiratory and expiratory pressures FEV1 and forced vital capacity (FVC) were measured using an EasyOne® spirometer (NDD Medical Technologies, Zurich, Switzerland). Strength of respiratory muscles was measured with a manuvacoumeter (MicroRPM, Carefusion®, San Diego, CA, USA) as MIP and MEP. Differences between the two highest values of FEV1, FVC, MIP, and MEP were less than 5%. All measurements were performed according to guidelines prescribed by American Thoracic Society, European Respiratory Society (2002, 2005). Maximal voluntary isometric contraction Subjects sat on a table with an adjustable chair back with right leg fixed, with a knee joint angle of 90° of flexion, and ankle attached just superior to malleoli to a strain gauge (Tedea-Huntleigh, Cardiff, UK). Subjects performed four 3–4 s MVCs, with 1 min rest between contractions. To ensure that subjects remained in same position during MVC, three Velcro strips were tied around chest, hip, and thighs. In order to reduce day-today variation, exact body position of subjects were reg-

istered and used throughout entire experiment. Before MVC measurements, subjects performed three 60% submaximal isometric contractions for a duration of 3–4 s. Isometric endurance Subjects sat on a table with straight backs and right arm pointing straight forward, so that ankle between arm and thorax was 90°. Velcro strips were used to ensure that subjects remained in same position during the entire test. The test started after a 3 s countdown from investigator after which subjects held a 3 kg dumbbell in straight arm. A horizontal aluminum bar was positioned 10 cm below right arm of subjects, and the test was stopped first time arm touched the bar. Repeated Wingate test Repeated sprint ability was determined in a repeated Wingate test. Protocol was custom made in Monark 839E analysis software. Twenty seconds before each of the three consecutive bouts, subjects were told to find and maintain a cadence of 70 rpm until onset of the Wingate test. Three seconds before the start of each bout, test leader would count down, after which subjects would pedal as fast as possible for 30 s against a resistance corresponding to 0.75 N·kgbw. During the 2 min of passive recovery, workload was set to 6 N. Subjects were instructed to remain seated throughout the entire test. Cadence and power output were recorded by a computer with a sampling frequency of 1 Hz. Following the test, subjects’ peak power (highest power output achieved for five consecutive seconds), mean power (average power output during the entire test), and fatigue index (difference between peak power and lowest power divided by peak power during each test) were calculated. Statistics Sample size was determined for SAL for the primary response variable (peak power) in a repeated measures analysis of variance (ANOVA) design. The effect size and standard deviation were chosen based on previous literature investigating the acute (Collomp et al., 2005) and short-term (Le Panse et al., 2005) effects of oral salbutamol on peak power. Correlation patterns were specified between the repeated measurements. Calculations were made in GLIMMPSE (University of Florida, USA). To detect a difference in SAL, at least nine subjects should be included, and with a risk of having one drop out, we included 10 subjects in SAL as well as 10 in PLA. Data were analyzed in SPSS statistical software, version 22 (IBM Software, Chicago, Illinois, USA). Data are presented as mean ± standard error of the mean, and were tested for normality with a Sharipo–Wilk test and Q-Q plots. To determine differences in VO2max and Wmax between the groups before the intervention, an

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Hostrup et al. unpaired t-test was used. Differences in VO2max and body mass before and after the intervention were tested with a repeated-measures ANOVA with group and trial as the two factors. Differences in peak power, mean power, and fatigue indices during the repeated Wingate test were determined by a repeated-measures ANOVA with group, Wingate number (W1, W2, and W3), and trial (baseline, acute, and two-week) as the three factors. A repeatedmeasures ANOVA was used to detect differences in MVC, exercise performance at 110% of VO2max, isometric endurance, and MIP/MEP with group and trial as the two factors. To determine differences in venous blood concentrations, a repeated-measures ANOVA was used with group, time (sampling point), and trial (baseline, acute, and two-week) as the three factors. In case of a significant interaction, the Newman–Keuls method was used as a post-hoc test. Level of significance was defined as α < 0.05. Results Side effects, body mass, and VO2max SAL experienced only minor acute side effects, including tremor and tachycardia. During the intervention, these side effects surpassed within a few days. No side effects were reported in PLA. Subjects’ body mass did not change with the intervention, being 75.1 ± 1.6 and 75.4 ± 1.4 kg before and after the intervention in SAL and 72.8 ± 2.0 and 72.7 ± 1.8 kg in PLA, respectively. No changes were observed in VO2max and iPPO with the intervention in either group. In SAL, VO2max and iPPO were 69.5 ± 1.9 and 69.7 ± 1.9 mL/min/kg and 449 ± 9 and 446 ± 9 W before and after the intervention, respectively, with the

corresponding values in PLA being 69.3 ± 1.8 and 69.2 ± 1.5 mL/min/kg and 432 ± 9 and 429 ± 9 W. Repeated Wingate test There was a significant interaction between group and trial (P < 0.05) on Wingate peak power. After 2-week administration, SAL increased peak power during the first (P < 0.05) and second bout (P < 0.05) by 6.4 ± 2.0 and 4.2 ± 1.0%. Acute administration only increased (P < 0.05) peak power during the first bout by 4.1 ± 1.7% in SAL (Fig. 1). No differences were observed in peak power during third bout in SAL. Mean power and fatigue indices did not change with the intervention in SAL (Table 2). Performance did not change during the intervention in PLA. Maximal voluntary isometric contraction MVC did not change with the intervention in either group (Fig. 2). Exercise performance at 110% of VO2max No differences were observed in time to exhaustion during exercise at 110% of VO2max in either group. In SAL, subjects performed 266 ± 21 s at baseline and 225 ± 23 and 233 ± 24 s after acute and 2-week administration, respectively. In PLA, performance was 215 ± 16, 197 ± 17, and 202 ± 23 s at baseline, acute, and 2-week administration, respectively. Isometric endurance In SAL, time to exhaustion during isometric contraction of m. deltoideus was 118 ± 9, 120 ± 8, and 118 ± 8 s at

Fig. 1. Peak power during three repeated Wingate tests interspersed by 2 min of recovery at baseline and after acute and 2-week administration of either salbutamol (SAL, n = 10) (filled bars) or placebo (PLA, n = 10) (open bars). W1, first Wingate test; W2, second Wingate test; W3, third Wingate test. Three-factorial analysis of variance showed a significant interaction (P < 0.05) between group and trial. *Significant (P < 0.05) difference from baseline in SAL. Mean ± standard error of the mean.

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Role of salbutamol on performance in athletes Table 2. Performance measurement during three repeated Wingate tests

W1

SAL (n = 10) Mean power (W) Fatigue index (%) PLA (n = 10) Mean power (W) Fatigue index (%)

W2

W3

Baseline

Acute

Two-week

Baseline

Acute

Two-week

Baseline

Acute

Two-week

688 ± 17 39 ± 1

695 ± 11 40 ± 2

690 ± 13 40 ± 2

640 ± 11 44 ± 2

632 ± 10 44 ± 2

630 ± 11 47 ± 2

606 ± 11 46 ± 2

602 ± 9 46 ± 1

601 ± 12 48 ± 2

682 ± 14 41 ± 2

672 ± 17 41 ± 3

669 ± 16 43 ± 3

611 ± 15 47 ± 2

614 ± 16 48 ± 3

609 ± 15 49 ± 4

567 ± 17 50 ± 2

574 ± 16 50 ± 3

570 ± 15 48 ± 3

Mean power and fatigue indices in salbutamol (SAL) and placebo (PLA). Mean ± standard error of the mean.

(W1) and during endurance exercise at 110% of VO2max (Tables 3 and 4). No changes were observed in PLA with the intervention (not presented). Discussion

Fig. 2. Maximal isometric voluntary contraction of m. quadriceps at baseline and after acute and 2-week administration of either salbutamol (SAL, n = 10) (filled bars) or placebo (PLA, n = 10) (open bars). Mean ± standard error of the mean.

baseline, acute, and 2-week administration, respectively, with corresponding values being 128 ± 9, 125 ± 10, and 129 ± 8 s in PLA, respectively. Maximal inspiratory and expiratory pressures No differences were observed in MIP and MEP between the groups with the intervention. MIP was 133 ± 6, 135 ± 6, and 144 ± 7 cm H2O at baseline, after acute administration, and after 2-week administration in SAL, respectively, with the corresponding values being 130 ± 11, 135 ± 11, and 133 ± 13 cm H2O in PLA. MEP was 181 ± 16, 186 ± 14, and 191 ± 15 cm H2O, at baseline, after acute administration, and after 2-week administration in SAL, respectively, with the corresponding values being 172 ± 10, 172 ± 11, and 173 ± 12 cm H2O in PLA. Plasma lactate, glucose, and K+ No differences were observed in plasma glucose and lactate neither at rest nor during exercise in SAL during with the intervention. A significant interaction (P < 0.05) between group and trial was observed in plasma K+. Acute administration in SAL decreased (P < 0.05) plasma K+ at rest, after the first bout in the Wingate test

The most important findings of the present study were that acute and 2-week administration of oral salbutamol improved peak power during the first Wingate test, but that this effect disappeared as sprints were repeated. In addition, oral salbutamol had no effect on quadriceps isometric muscle strength, exercise performance at 110% of VO2max, or on isometric endurance. While former studies have measured acute and shortterm effects of oral salbutamol on single sprint performance in recreational subjects (Collomp et al., 2005; Sanchez et al., 2012), we measured effects on repeated sprint performance in endurance athletes. Interestingly, although salbutamol improved athletes’ peak power during the first bout in the Wingate test after acute administration, peak power was equally attenuated for salbutamol as placebo when sprints were repeated, reaching similar peak power as baseline during the second and third sprint. This observation was also the case following 2-week administration in SAL, although peak power also was increased compared with baseline during the second sprint. The reason for these observations might be related to the greater initial sprint performance with salbutamol during the first bouts, giving rise to greater muscular perturbations of ions and accumulation of metabolites causing fatigue (Gaitanos et al., 1993; Mendez-Villanueva et al., 2007), thus blunting the effect of salbutamol on peak power during the last sprint. In support of this proposition, initial sprint performance has been found to be positively correlated with performance decrement over subsequent sprints (Girard et al., 2011). Our observations of increased Wingate peak power following both acute and short-term administration of oral salbutamol in endurance athletes are consistent with observations from recreational subjects (Collomp et al., 2005; Sanchez et al., 2012). However, on the contrary to the observations in recreational subjects (Sanchez et al., 2012), we observed a larger effect of oral salbutamol following short-term administration than after acute

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Hostrup et al. Table 3. Plasma concentrations of lactate, glucose and K+ at rest, during, and after three repeated Wingate tests in SAL

(mmol/L) Lactate Baseline Acute Two-week Glucose Baseline Acute Two-week K+ Baseline Acute Two-week

Pre

W1

R1

W2

R2

W3

P5

P15

2.0 ± 0.3 2.2 ± 0.2 2.1 ± 0.2

2.8 ± 0.4 3.2 ± 0.4 3.6 ± 0.7

7.7 ± 0.7 7.5 ± 0.4 8.4 ± 0.7

9.6 ± 1.0 10.0 ± 1.0 10.0 ± 1.1

12.4 ± 0.9 12.9 ± 0.7 13.0 ± 0.6

13.8 ± 1.2 14.1 ± 1.0 14.2 ± 1.2

16.4 ± 1.0 16.2 ± 0.8 16.2 ± 1.0

14.2 ± 1.3 13.0 ± 1.0 12.8 ± 1.2

4.9 ± 0.2 5.5 ± 0.2 5.2 ± 0.2

5.0 ± 0.1 5.5 ± 0.2 5.1 ± 0.3

5.1 ± 0.2 5.5 ± 0.2 5.1 ± 0.3

5.3 ± 0.2 5.7 ± 0.2 5.3 ± 0.2

5.5 ± 0.2 5.9 ± 0.2 5.5 ± 0.3

5.8 ± 0.2 6.1 ± 0.2 5.7 ± 0.3

6.0 ± 0.3 6.5 ± 0.3 6.1 ± 0.4

5.4 ± 0.3 6.0 ± 0.3 5.3 ± 0.3

3.7 ± 0.1 3.4 ± 0.1* 3.7 ± 0.1

5.2 ± 0.3 5.2 ± 0.3 5.3 ± 0.4

4.0 ± 0.1 3.8 ± 0.1† 4.0 ± 0.1

5.2 ± 0.3 5.2 ± 0.3 5.3 ± 0.3

3.9 ± 0.1 3.8 ± 0.1 4.0 ± 0.1

5.0 ± 0.3 5.0 ± 0.2 5.2 ± 0.3

3.2 ± 0.1 3.3 ± 0.1 3.5 ± 0.1

3.5 ± 0.1 3.5 ± 0.1 3.6 ± 0.1

*Significant (P < 0.05) difference from baseline in SAL. † Significant (P < 0.05) difference from baseline and 2-week administration in SAL. P5 and P15, blood drawn 5 and 15 min after last test; Pre, blood drawn before the first test; R1 and R2, blood drawn 2 min after the first (R1) and second (R2) Wingate test, respectively; SAL, salbutamol; W1, W2 and W3, blood drawn immediately after the first (W1), second (W2) and third (W3) Wingate test, respectively. Three-factorial analysis of variance revealed a significant interaction (P < 0.05) between group and trial for plasma K+. Mean ± standard error of the mean. Table 4. Plasma concentrations of lactate, glucose and K+ at rest, during, and after exercise at 110% VO2max in SAL

(mmol/L) Lactate Baseline Acute Two-week Glucose Baseline Acute Two-week K+ Baseline Acute Two-week

Pre

EX1

R1

EX2

R2

EX3

P5

P15

1.3 ± 0.1 1.4 ± 0.1 1.6 ± 0.2

2.5 ± 0.3 3.4 ± 0.3 3.1 ± 0.3

5.2 ± 0.5 6.3 ± 0.5 6.1 ± 0.5

6.7 ± 0.4 6.9 ± 0.5 7.7 ± 0.6

8.1 ± 0.8 9.3 ± 0.8 9.6 ± 0.9

13.6 ± 0.9 13.8 ± 0.8 14.2 ± 0.9

14.2 ± 0.8 14.2 ± 1.0 14.7 ± 0.9

10.8 ± 1.0 10.8 ± 1.0 10.5 ± 1.0

4.9 ± 0.2 4.9 ± 0.2 5.1 ± 0.1

5.1 ± 0.1 5.2 ± 0.2 5.2 ± 0.2

5.2 ± 0.1 5.5 ± 0.2 5.4 ± 0.2

5.2 ± 0.1 5.3 ± 0.2 5.3 ± 0.2

5.6 ± 0.2 5.7 ± 0.2 5.5 ± 0.3

5.5 ± 0.2 5.6 ± 0.3 5.4 ± 0.3

7.0 ± 0.4 6.8 ± 0.4 6.7 ± 0.3

6.3 ± 0.3 6.3 ± 0.3 5.8 ± 0.4

3.7 ± 0.1 3.3 ± 0.1* 3.5 ± 0.1

4.7 ± 0.1 4.0 ± 0.1* 4.3 ± 0.1

4.1 ± 0.2 4.0 ± 0.2 3.9 ± 0.1

4.7 ± 0.1 4.2 ± 0.2 4.4 ± 0.1

4.2 ± 0.1 3.7 ± 0.1* 3.8 ± 0.1

5.5 ± 0.2 5.1 ± 0.1† 5.7 ± 0.2

3.6 ± 0.1 3.3 ± 0.1 3.5 ± 0.1

3.8 ± 0.1 3.8 ± 0.4 3.6 ± 0.1

*Significant (P < 0.05) difference from baseline in SAL. † Significant (P < 0.05) difference from baseline and 2-week administration in SAL. EX1, EX2 and EX3, blood drawn at the end of each bout; P5 and P15, blood drawn 5 and 15 min after last test; Pre, blood drawn before the first test; R1 and R2, at the end of 2 min of recovery between each bout; SAL, salbutamol; VO2max, maximal oxygen uptake. Three-factorial analysis of variance revealed a significant interaction (P < 0.05) between group and trial for plasma K+. Mean ± standard error of the mean.

administration. The contradictory observations might be explained by administration instructions. As such, the endurance athletes in the present study were asked to ingest the study drugs 2 h before each training session, whereas in the study by Sanchez et al. (2012) salbutamol was administered as 4 mg dosing at three fixed time points during the day, and not necessarily in combination with training. Therefore, the larger effect observed following 2-week administration in the present study might be explained by a larger training response induced by salbutamol during the 2-week ingestion. Although peak power was increased in SAL during the first sprints, no differences were observed in mean power or fatigue indices, neither after acute administration nor after 2-week administration. In contrast, former studies in recreational males and females (Collomp et al., 2005; Le Panse et al., 2007) have shown increases in mean power during a single Wingate test after acute adminis-

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tration of 4 mg salbutamol. The discrepancy could be attributed to differences in training status of the included subjects or in dosing. Noteworthy, beta2-adrenoceptor content has been shown to be lower in athletic subjects than in recreational (Butler et al., 1982). This is also supported by the increase of 4.1 ± 1.7% observed in peak power during the first sprint after acute administration of salbutamol in the present study, being lower than that observed in the previous studies in recreational subjects showing increases of 9.4% (Collomp et al., 2005) and 14% (Sanchez et al., 2012). Still, our observations of no differences in mean power and fatigue indices following 2-week administration of salbutamol are in agreement with prior studies in recreational subjects showing no effects of short-term administration of salbutamol (Le Panse et al., 2005). This discrepancy might also explain why we observed no differences in blood lactate following the Wingate tests as observed in the study by Le

Role of salbutamol on performance in athletes Panse et al. (2007). Still, in line with the present observations, Collomp et al. (2005) observed no differences in blood lactate between oral salbutamol and placebo following a Wingate test. The increased peak power observed during the Wingate test in SAL could be attributed to various effects in skeletal muscles. In animal models, administration of beta2-agonists have been shown to stimulate excitation-contraction coupling (Cairns & Dulhunty, 1993) by protein kinase A dependent phosphorylation of dihydropyridine receptors and ryanodine receptors (Ha et al., 1999) leading to elevated Ca2+ release (Van Der Heijden et al., 1998). In addition, inhibitory effects of phospholamban on SERCA-ATPase are attenuated by beta2-adrernegic stimulation (Slack et al., 1997), hence accelerating rate of relaxation. In support of the latter, Crivelli et al. (2011) reported a shorter half relaxation time after administration of 6 mg salbutamol measured during MVC of m. quadriceps with electrical stimulation in active males. Although not investigated in human, increased Ca2+ handling caused by beta2-adrenergic stimulation might explain the greater peak power observed with salbutamol during Wingate sprint through enhanced muscle shortening velocity and rate of relaxation (Crivelli et al., 2011). Higher peak power during Wingate tests might also arise from elevated rate of glycogenolysis and glycolysis as beta2-agonists potentially increase anaerobic energy yield (Richter et al., 1982; Alves & Sola-Penna, 2003). We observed no effects of acute and 2-week administration of salbutamol on MVC of m. quadriceps. In agreement with the present study, Crivelli et al. (2011) and Decorte et al. (2008) found no acute effects of salbutamol on isometric muscle strength (Decorte et al., 2008; Crivelli et al., 2011). However, van Baak et al. (2000) observed an increase in isokinetic muscle strength in active males after acute administration of 4 mg salbutamol, and recently, Kalsen et al. (2013) observed a 6% increase in MVC of m. quadriceps in elite swimmers after acute combined inhalation of three different beta2-agonists in doses within the current WADA regulations. Moreover, previous studies reported increased muscle strength following short-term administration of oral salbutamol in recreational subjects. Caruso et al. (2008) observed that concentric and eccentric force, measured by flywheel, were greater after 40 days of unilateral inactivity combined with oral administration of albuterol (Caruso et al., 2008). In addition, muscle force was shown to increase after 9 weeks of knee extension training when salbutamol (16 mg) was administered during the last 6 weeks (Caruso et al., 1995). The discrepancy between the present study and the previous by Caruso et al. might be related to differences in dose and duration of administration. In the studies by Caruso et al., 16 mg oral salbutamol was administered, thus being twice as high as the 8 mg in the present study. Moreover, the duration of administration

was longer in the studies by Caruso et al. Lastly, the subjects that participated in the present study were more trained than those included in the studies by Caruso et al., perhaps responding differently as discussed above. Nonetheless, work in animal studies have demonstrated that short-term administration of high doses of beta2agonists increase muscle mass and cause a shift towards more fast twitch muscle fibers, which may explain the observations by Caruso et al. (Zhang et al., 1996). In any case, the underlying mechanisms by which short-term administration of oral salbutamol affects muscle strength in humans need to be clarified in future studies. To our knowledge, this is the first study investigating effects of oral salbutamol on isometric endurance. It has been proposed that occlusion of blood flow to skeletal muscles during isometric contractions (Humphreys & Lind, 1963) limits the release of K+ to the blood stream (Clausen, 2008), and consequently, removal of interstitial K+ would be restricted to Na+/K+-ATPase activity. As such, our hypothesis was that salbutamol would induce a stimulatory effect on Na+/K+-ATPase activity leading to reduced accumulation of interstitial K+ and delay development of fatigue (Clausen, 2003; Nielsen et al., 2004). Although, Na+/K+-ATPase activity might have been increased with salbutamol, also supported by the lower venous K+ concentrations, no differences were observed on endurance, and apparently, salbutamol does not seem to have an effect on isometric endurance. While several former studies have reported improvements in exercise performance after both acute and short-term administration of oral salbutamol in recreational subjects (Collomp et al., 2000; van Baak et al., 2000), we observed no differences in exercise performance at 110% of VO2max in endurance athletes. The difference may be explained by several factors. Firstly, intensity of the endurance test was higher in the present study than intensities applied in former studies ranging from 70 to 85% of VO2max (Collomp et al., 2000; van Baak et al., 2000). Secondly, subjects in the present study were more trained than those included in former studies of oral beta2-agonists. Still, in agreement with our results, Collomp et al. (2002) found no effect of 6 mg oral salbutamol on exercise performance in trained men. We observed no effects of oral salbutamol on MIP and MEP. Our observations are inconsistent with the observations by Martineau et al. (1992) showing an increase in MIP following 2- and 3-week administration of oral salbutamol. However, in agreement with the present observations, they did not observe any difference in MEP. In summary, acute and 2-week administration of oral salbutamol increases peak power during first bouts in a repeated Wingate test, but this effect disappear as bouts are repeated. However, on contrary with former studies, we observed no effects of oral salbutamol on exercise performance. Lastly, we observed no effects on

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Hostrup et al. MVC and isometric endurance of m. deltoideus with salbutamol. Nevertheless, our observations suggest that oral salbutamol provide athletes an advantage in sport disciplines requiring a high power development. Future studies should clarify molecular mechanisms behind increases peak power with beta2-agonists. Perspectives The present study adds new information about salbutamol in the context of doping in competitive sports. While effects of oral salbutamol have been well described in non-elite subjects, the present study is the first to investigate effects in elite endurance athletes. Along with prior studies in recreational subjects, our observations of enhanced peak power during repeated Wingate tests supports the restriction of oral salbutamol on WADA’s list of prohibited substances. Importantly, some subjects experience side effects such as muscle tremor and tachycardia following intake of oral salbutamol, which potentially can have a negative impact on athletes’ health and performance (Le Panse et al., 2007). Although therapeutic inhalation of salbutamol still is allowed in competitive sports, future studies should investigate effects of inhaled beta2-agonists on sprint performance and muscle strength to rule out an ergogenic effect. From a pharmacological perspective, it seems plausible that inhaled beta2-agonists could be

performance-enhancing on peak power during maximal sprinting. Indeed, Kalsen et al. (2013) recently demonstrated that combined inhalation of beta2-agonists within the current WADA thresholds increased arm sprint ergometer performance. Furthermore, Decorte et al. (2013) also recently demonstrated that inhalation of only 800 μg salbutamol increased quadriceps endurance. As such, athletes might unfairly benefit from salbutamol, even when used within the current limits on the list of prohibited substances. Key words: Beta2-agonists, doping, athletes, muscle strength, peak power.

Acknowledgements The study was supported by a grant from the World Anti-doping Agency (WADA).

Author contribution MH, AK, JB, and VB participated in the study design. MH, AK, MA, VB, and JB conducted the experiments. VB was responsible for medical expertise and screening of the athletes. MH, AK, MA, JB and VB performed the data analysis. MH, AK, MA, VB, and JB wrote or contributed to the writing of the manuscript.

References Alves GG, Sola-Penna M. Epinephrine modulates cellular distribution of muscle phosphofructokinase. Mol Genet Metab 2003: 78: 302–306. American Thoracic Society, European Respiratory Society. ATS/ERS statement on respiratory muscle testing. Am J Respir Crit Care Med 2002: 166: 518–624. American Thoracic Society, European Respiratory Society. ATS/ERS recommendations for standardized procedures for the online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide, 2005. Am J Respir Crit Care Med 2005: 171: 912–930. Atkinson G, Davison R, Jeukendrup A, Passfield L. Science and cycling: current knowledge and future directions for research. J Sports Sci 2003: 21: 767–787. Butler J, O’Brien M, O’Malley K, Kelly JG. Relationship of beta-adrenoreceptor density to fitness in athletes. Nature 1982: 298: 60–62. Cairns SP, Dulhunty AF. The effects of beta-adrenoceptor activation on contraction in isolated fast- and slow-twitch skeletal muscle fibres of

8

the rat. Br J Pharmacol 1993: 110: 1133–1141. Carlsen KH, Anderson SD, Bjermer L, Bonini S, Brusasco V, Canonica W, Cummiskey J, Delgado L, Del Giacco SR, Drobnic F, Haahtela T, Larsson K, Palange P, Popov T, van Cauwenberge P. European Respiratory Society; European Academy of Allergy and Clinical Immunology, GA(2)LEN. Treatment of exercise-induced asthma, respiratory and allergic disorders in sports and the relationship to doping: part II of the report from the Joint Task Force of European Respiratory Society (ERS) and European Academy of Allergy and Clinical Immunology (EAACI) in cooperation with GA(2)LEN. Allergy 2008: 63: 492–505. Caruso JF, Hamill JL, Yamauchi M, Cook TD, Mercado DR, Wickel EE. Albuterol and exercise effects on ankle extensor strength during 40 days of unloading. Aviat Space Environ Med 2008: 79: 577–584. Caruso JF, Signorile JF, Perry AC, Leblanc B, Williams R, Clark M, Bamman MM. The effects of albuterol and isokinetic exercise on the

quadriceps muscle group. Med Sci Sports Exerc 1995: 27: 1471–1476. Clausen T. Na+-K+ pump regulation and skeletal muscle contractility. Physiol Rev 2003: 83: 1269–1324. Clausen T. Clearance of extracellular K+ during muscle contraction-roles of membrane transport and diffusion. J Gen Physiol 2008: 13: 473–481. Collomp K, Candau R, Collomp R, Carra J, Lasne F, Préfaut C, De Ceaurriz J. Effects of acute ingestion of salbutamol during submaximal exercise. Int J Sports Med 2000: 21: 480–484. Collomp K, Candau R, Millet G, Mucci P, Borrani F, Préfaut C, De Ceaurriz J. Effects of salbutamol and caffeine ingestion on exercise metabolism and performance. Int J Sports Med 2002: 23: 549–554. Collomp K, Le Panse B, Portier H, Lecoq AM, Jaffre C, Richard O, Benhamou L, Courteix D, De Ceaurriz J. Effects of acute salbutamol intake during a Wingate test. Int J Sports Med 2005: 26: 513–517. Crivelli G, Millet GP, Gremion G, Borrani F. Effects of salbutamol on the contractile properties of human skeletal

Role of salbutamol on performance in athletes muscle before and after fatigue. Acta Physiol 2011: 203: 311–320. Decorte N, Bachasson D, Guinot M, Flore P, Levy P, Verges S, Wuyam B. Effect of salbutamol on neuromuscular function in endurance athletes. Med Sci Sports Exerc 2013: 45: 1925–1932. Decorte N, Verges S, Flore P, Guinot M, Wuyam B. Effects of acute salbutamol inhalation on quadriceps force and fatigability. Med Sci Sports Exerc 2008: 40: 1220–1227. Elers J, Pedersen L, Henninge J, Hemmersbach P, Dalhoff K, Backer V. The pharmacokinetic profile of inhaled and oral salbutamol in elite athletes with asthma and nonasthmatic subjects. Clin J Sport Med 2012a: 22: 140–145. Elers J, Pedersen L, Henninge J, Lund TK, Hemmersbach P, Dalhoff K, Backer V. Blood and urinary concentrations of salbutamol in asthmatic subjects. Med Sci Sports Exerc 2010: 42: 244–249. Gaitanos GC, Williams C, Boobis LH, Brooks S. Human muscle metabolism during intermittent maximal exercise. J Appl Physiol 1993: 75: 712–719. Girard O, Mendez-Villanueva A, Bishop D. Repeated-sprint ability – part I: factors contributing to fatigue. Sports Med 2011: 41: 673–694. Ha TNV, Posterino GS, Fryer MW. Effects of terbutaline on force and intracellular calcium in slow-twitch skeletal muscle fibres of the rat. Br J Pharmacol 1999: 126: 1717–1724. Hostrup M, Kalsen A, Auchenberg M, Rzeppa S, Hemmersbach P, Bangsbo J, Backer V. Urine concentrations of oral salbutamol in samples collected after intense exercise in endurance athletes. Drug Test Anal. 2014: 6: 528–532. Humphreys PW, Lind AR. The blood flow through active and inactive muscles of the forearm during sustained hand-grip contractions. J Physiol 1963: 166: 120–135.

Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. J Physiol 2008: 586: 35–44. Kalsen A, Hostrup M, Bangsbo J, Backer V. Combined inhalation of beta2 -agonists improves swim ergometer sprint performance but not high-intensity swim performance. Scand J Med Sci Sports 2013: doi: 10.1111/sms.12096 Le Panse B, Arlettaz A, Portier H, Lecoq AM, De Ceaurriz J, Collomp K. Effects of acute salbutamol intake during supramaximal exercise in women. Br J Sports Med 2007: 41: 430–434. Le Panse B, Collomp K, Portier H, Lecoq AM, Jaffre C, Beaupied H, Richard O, Benhamou L, De Ceaurriz J, Courteix D. Effects of short-term salbutamol ingestion during a Wingate test. Int J Sports Med 2005: 26: 518–523. Martineau L, Horan MA, Rothwell NJ, Little RA. Salbutamol, a beta 2-adrenoceptor agonist, increases skeletal muscle strength in young men. Clin Sci 1992: 83: 615–621. McKenzie DC, Fitch KD. The asthmatic athlete: inhaled beta-2 agonists, sport performance, and doping. Clin J Sport Med 2011: 21: 46–50. Mendez-Villanueva A, Hamer P, Bishop D. Fatigue responses during repeated sprints matched for initial mechanical output. Med Sci Sports Exerc 2007: 39: 2219–2225. Nielsen JJ, Mohr M, Klarskov C, Kristensen M, Krustrup P, Juel C, Bangsbo J. Effects of high-intensity intermittent training on potassium kinetics and performance in human skeletal muscle. J Physiol 2004: 554: 857–870. Pluim B, de Hon O, Staal B, Limpens J, Kuipers H, Overbeek S, Zwinderman A, Scholten R. β2-agonists and

physical performance: a systematic review and meta-analysis of randomized controlled trials. Sports Med 2011: 41: 39–57. Richter EA, Ruderman NB, Gavras H, Belur ER, Galbo H. Muscle glycogenolysis during exercise: dual control by epinephrine and contractions. American Journal of Physiology 1982: 242: 25–32. Sanchez AM, Collomp K, Carra J, Borrani F, Coste O, Préfaut C, Candau R. Effect of acute and short-term oral salbutamol treatments on maximal power output in non-asthmatic athletes. Eur J Appl Physiol 2012: 112: 3251–3258. Slack JP, Grupp IL, Ferguson DG, Rosenthal N, Kranias EG. Ectopic expression of phospholamban in fast-twitch skeletal muscle alters sarcoplasmic reticulum Ca2+ transport and muscle relaxation. J Biol Chem 1997: 272: 18862–18868. van Baak MA, Mayer LH, Kempinski RE, Hartgens F. Effect of salbutamol on muscle strength and endurance performance in non asthmatic men. Med Sci Sports Exerc 2000: 32: 1300–1306. Van Der Heijden HF, Zhan WZ, Prakash YS, Dekhuijzen PN, Sieck GC. Salbutamol enhances isotonic contractile properties of rat diaphragm muscle. J Appl Physiol 1998: 85: 525–529. Wolfarth B, Wuestenfeld JC, Kindermann W. Ergogenic effects of inhaled beta2-agonists in non-asthmatic athletes. Endocrinol Metab Clin North Am 2010: 39: 75–87. Zhang KM, Hu P, Wang SW, Feher JJ, Wright LD, Wechsler AS, Spratt JA, Briggs FN. Salbutamol changes the molecular and mechanical properties of canine skeletal muscle. J Physiol 1996: 496: 211–220.

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Effects of acute and 2-week administration of oral salbutamol on exercise performance and muscle strength in athletes.

Our objective was to investigate effects of acute and 2-week administration of oral salbutamol on repeated sprint ability, exercise performance, and m...
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