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Physiological and metabolic responses as function of the mechanical load in resistance exercise
Buitrago, Sebastian1; Wirtz, Nicolas1; Flenker, Ulrich2; Kleinöder, Heinz1
1
Institute of Training Science and Sport Informatics, German Sport University
Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany. [email protected] 2
Institute of Biochemistry, German Sport University Cologne, Am Sportpark
Müngersdorf 6, 50933 Cologne, Germany
Corresponding Author: Sebastian Buitrago Aachener Straße 1041, 50858 Cologne, Germany Phone: 0049-221-8236325 E-Mail: [email protected]
Address and affiliation of the first and corresponding author differs from that at the time of the study
1
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Abstract The present study aimed to investigate the relationship between the mechanical load during resistance exercise and the elicited physiological responses. Ten resistance trained healthy male subjects performed one set of resistance exercise each at 55%, 70% and 85% of 1 repetition maximum (1RM) for as many repetitions as possible and in four training modes: 4-1-4-1 (4 s concentric, 1 s isometric, 4 s eccentric and 1 s isometric successive actions), 2-1-2-1, 1-1-1-1 and explosive (maximum velocity concentric). Mean concentric power (MCP) and total concentric work (TCW) were determined. Oxygen uptake ( V& O 2 ) was measured during exercise and for 30 minutes post exercise. Total volume of consumed oxygen (O2-consumed) and excess post exercise oxygen consumption (EPOC) were calculated. Maximum blood lactate concentration (LAmax) was also determined. V& O 2 exhibited a linear dependency on mean concentric power. Mean concentric power did not have a detectable effect on EPOC and LAmax. An augmentation of total concentric work resulted in significant linear increase of O2-consumed and EPOC. Total concentric work caused a significant increase in LAmax. In general, a higher mechanical load induced a larger physiological response. An increase in mean concentric power elicited higher aerobic energy turnover rates. However, a higher extent of total concentric work augments total energy cost covered by oxidative and/or glycolytic pathways.
Key Words: oxygen uptake; blood lactate concentration; power; work; intensity
2
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Introduction The acute responses of energy expenditure to different forms of resistance exercise and their underlying metabolic mechanisms have been investigated in numerous studies (Ballor et al. 1987; Beckham and Earnest 2000; Binzen et al. 2001; Wilmore et al. 1978). The physiological and metabolic responses to resistance exercise are caused by mechanical stimuli, which among other factors are determined by the external load and the contraction velocity (Toigo and Boutellier 2006). Several studies have reported the responses of oxygen uptake ( V& O 2 ), rate of energy expenditure, blood lactate concentration (LA), and excess post-exercise oxygen consumption (EPOC) to varying loads (Buitrago et al. 2012; Hunter et al. 1988; Kalb and Hunter 1991; Kang et al. 2005; Mazzetti et al. 2007; Ratamess et al. 2007; Thornton and Potteiger 2002; Willoughby et al. 1991) and contraction velocities (Ballor et al. 1987; Buitrago et al. 2012; Hunter et al. 2003; Mazzetti et al. 2007). External load and movement velocity determine the generated power and the performed work, largely determining the energy demands of exercise. The measurement of the movement velocity and the applied force enables the calculation of the generated power and the performed work during resistance exercise. Hence, several studies with different objectives have investigated the mechanical characteristics of different resistance exercises and loading schemes (Cormie et al. 2007; Harris et al. 2007; Kawamori et al. 2006; Thomas et al. 2007). For steady state/rate endurance type exercise, especially cycling and upper body exercise, the relationship between the mechanical output (e.g. power and work) and the responses of energy metabolism has been described in numerous studies (Chavarren and Calbet 1999; Francescato et al. 2003; Gaesser and Brooks 1975; Hansen et al. 1988; Kang et al. 1999). However, the measurement of mechanical variables on 3
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Page 4 of 26
resistance machines requires a more complex apparatus when compared to cycling and arm crank ergometers. Several investigations have conducted dynamometric online measurements during non isokinetic resistance exercise (Cormie et al. 2007; Harris et al. 2007; Kawamori et al. 2006; Petrella et al. 2005). Accordingly, to date, no study has specifically examined the relationship between the generated mechanical output and the corresponding elicited physiological and metabolic responses. To describe extensively the mechanical load/physiological response relationship, different resistance exercise schemes covering a wide range of external load and movement velocities have to be analysed. Furthermore, a determination and quantification of the generated mechanical output and the responses related to energy metabolism is needed Therefore, the purpose of the present investigation was to study in detail the physiological responses during and after resistance exercise as a function of the mechanical output. For the first time, a description of the relationship between the quantified, external mechanical stimuli and their associated responses of energy metabolism is expected. It was hypothesized that increases in mechanical load are attended by an elevation of the corresponding physiological and metabolic responses. The data will enable a deeper insight into of the underlying metabolism of resistance exercise, independent from the executed exercise protocol.
Materials and methods Subjects Ten healthy and resistance trained male subjects (age: 27.3 ± 3.2 years; height: 181.4 ± 4.8 cm; body mass: 81.4 ± 10.1 kg) participated in the investigation. All participants had several years of resistance training experience. The participants 4
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were informed about content, aims and risks of the investigation and they signed an informed consent document prior to any testing. The study was performed in accordance with the declaration of Helsinki and it was approved by the Ethics Committee of the German Sport University Cologne.
Experimental Design The participants reported to the laboratory on 13 separate days between 7:00 and 10:00 a.m. after an overnight fast. Only water was allowed to be consumed ad libitum and subjects were instructed not to perform any physical activity the morning prior to testing. On day one all participants were subjected to pre testing measurements. On the other twelve days of the investigation they performed one bout of a resistance exercise on a seated chest press machine. On each testing day they lifted one out of three different external loads, 55%, 70% or 85% of one repetition maximum (1 RM), at one of four given training modes, 4-1-4-1 (4-s concentric, 1-s isometric, 4-s eccentric and 1-s isometric successive actions), 2-1-2-1 (2-s concentric, 1-s isometric, 2-s eccentric and 1-s isometric successive actions), 1-1-1-1 (1-s concentric, 1-s isometric, 1-s eccentric and 1-s isometric successive actions) or explosive (maximum velocity concentric, 1-s isometric, 1-s eccentric and 1-s isometric successive actions).
Pre-testing measurements On pre-testing day anthropometric data was obtained. Body mass and body composition were determined via a digital scale and bioelectrical impendence analysis, respectively (TANITA corp., Tokyo, Japan). Afterwards subjects were seated and were connected to an open-circuit-gas-exchange measurement system.
5
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V& O 2 and V& CO 2 were measured for 30 minutes and data was collected during the last ten minutes to calculate basal metabolic rate (BMR). Following the respiratory measurements, subjects were seated on a chest press machine (gym80 international GmbH, Gelsenkirchen, Germany). The machine settings were adjusted individually so that all subjects had the same starting and end positions during pre-testing and during the experiment. For the starting position, seat height was adjusted so that the hand grip of the machine was at the height of the sternum. The angle between shoulder blade and upper arm was 180° and the inner elbow angle was 90°. The end position was defined by complete extension of the elbow. The range of motion (ROM) was measured by a linear transducer that was placed vertically between the upper weight plate of the weight stack and the frame of the strength machine. The transducer was connected to a PC and a visual feedback system (DigiMax GmbH, Hamm, Germany) recorded and stored each subject’s range of motion, defined as the vertical displacement of the weight stack during the lifting action. Subsequently, 1RM was determined using the testing protocol suggested and described by the American College of Sports Medicine (Whaley 2005).
Experimental procedures After randomly choosing an external load and a training mode, participants were seated in the chest press machine and were connected to the open gas-exchange measurement system. Five minutes after starting the gas-exchange measurement, a blood sample from the ear lobe was collected to determine blood lactate concentration (LA) at rest. Then a brief warm up session of 15 repetitions at 30% of 1RM was performed. Thereafter, the visual feedback tracking system was activated and subjects performed a few repetitions without any external load for the purpose of 6
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familiarization with the randomly selected training mode. The feedback system calculated and projected a tracking trace that moved according to the subjects’ range of motion and the set time for concentric, isometric and eccentric action. While executing concentric and eccentric actions, a tracking point in the display (controlled by the distance/velocity sensor) is moved up and down, respectively. By moving the tracking point at the adjusted speed the subjects followed the particularly calculated trace. The subjects were able to keep training mode constant during the complete exercise bout by using the permanent direct visual feedback. Before starting the exercise, subjects were instructed to exhale and inhale deeply during the concentric phase and eccentric phase, respectively.. During the 4-1-4-1 mode participants were instructed to conduct one complete breathing cycle (expiration and inspiration) during concentric action and during eccentric action, respectively. Ten minutes after beginning the gas-exchange measurement participants started to exercise. They were asked to maintain the effort until they failed to follow the tracking trace of the visual feedback system. In this case, participants were not able to sustain the given load and accordingly keep power constant. When exhaustion manifested this way, exercise was stopped and post exercise time started. Immediately after exercise, a capillary blood sample was taken. For a period of 30 minutes post exercise, blood sampling was repeated at intervals of two minutes. Breath-by-breath analyses were also finished 30 minutes post exercise. Fig. 1 shows the scheduled experimental protocol for one trial.
Measurements and calculations Mechanical force was measured by a dynamometer (DIGIMAX GmbH, Hamm, Germany) placed between weight stack and pull cable of the strength machine. Time 7
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and distance were measured by the same linear transducer of the visual feedback system. The dynamometer and transducer were calibrated prior to each test. Force, distance and time were recorded at a rate of 100Hz. Mean concentric power (MCP) and total concentric work (TCW) were calculated by a specific measuring system (MECHATRONIC GmbH, Hamm, Germany). Due to the differences in the lifted mass between the subjects, the force range obtained was large. Similarly, due to the differences in range of motion between subjects for the same training modes, a wide spectrum of velocities were obtained, generating a large amount of measured values for mean concentric power and total concentric work. Respiratory gas exchange measures were assessed via an open air gas-exchange measurement system in breath-by-breath mode (ZAN 680 CPX, ZAN GmbH, Oberthulba, Germany) throughout the testing, using standard algorithms with dynamic account for the time delay between the gas consumption and volume signal. The respiratory gas exchange instrumentation was calibrated according to the manufacturer's guidelines with calibration gas. Mean V& O 2 and volume of consumed O2 were calculated during exercise as well as for the 30 minutes post-exercise. EPOC was determined by subtracting BMR averaged over 30 minutes from consumed O2 post-exercise. Blood samples were analysed for LA with an enzymaticamperometric analyser (EBIO plus, EPPENDORF AG, Hamburg, Germany). The highest LA was defined as post-exercise maximum blood lactate concentration (LAmax).
Data Analysis Data was analysed by fitting linear mixed effects models (LME) (Pinheiro and Bates 2000). The software was “R” in the latest version 2.15.0 (The R Foundation for 8
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Statistical Computing; 2012). The “nlme” library was used for the LME functionality (Pinheiro et al. 2004). The mechanical variables mean concentric power and total concentric work served as predictors. The dependent variables were V& O 2 , O2, EPOC, and LAmax. Starting from simple linear relationships, higher order terms were added subsequently. Models were compared by likelihood statistics. When no improvement of the fit could be achieved, the simpler model was preferred, respectively. Random variation between the subjects was fundamentally modeled by assuming Gaussian distributed intercepts. Individual responses were accounted for by allowing for corresponding linear or higher order terms. Again, the simplest possible model was preferred in case of lack of improved fits.
Results
V& O 2 exhibited a linear dependency on mean concentric power (0.52 mL/W, p
Page 1 of 26
Physiological and metabolic responses as function of the mechanical load in resistance exercise
Buitrago, Sebastian1; Wirtz, Nicolas1; Flenker, Ulrich2; Kleinöder, Heinz1
1
Institute of Training Science and Sport Informatics, German Sport University
Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany. [email protected] 2
Institute of Biochemistry, German Sport University Cologne, Am Sportpark
Müngersdorf 6, 50933 Cologne, Germany
Corresponding Author: Sebastian Buitrago Aachener Straße 1041, 50858 Cologne, Germany Phone: 0049-221-8236325 E-Mail: [email protected]
Address and affiliation of the first and corresponding author differs from that at the time of the study
1
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Abstract The present study aimed to investigate the relationship between the mechanical load during resistance exercise and the elicited physiological responses. Ten resistance trained healthy male subjects performed one set of resistance exercise each at 55%, 70% and 85% of 1 repetition maximum (1RM) for as many repetitions as possible and in four training modes: 4-1-4-1 (4 s concentric, 1 s isometric, 4 s eccentric and 1 s isometric successive actions), 2-1-2-1, 1-1-1-1 and explosive (maximum velocity concentric). Mean concentric power (MCP) and total concentric work (TCW) were determined. Oxygen uptake ( V& O 2 ) was measured during exercise and for 30 minutes post exercise. Total volume of consumed oxygen (O2-consumed) and excess post exercise oxygen consumption (EPOC) were calculated. Maximum blood lactate concentration (LAmax) was also determined. V& O 2 exhibited a linear dependency on mean concentric power. Mean concentric power did not have a detectable effect on EPOC and LAmax. An augmentation of total concentric work resulted in significant linear increase of O2-consumed and EPOC. Total concentric work caused a significant increase in LAmax. In general, a higher mechanical load induced a larger physiological response. An increase in mean concentric power elicited higher aerobic energy turnover rates. However, a higher extent of total concentric work augments total energy cost covered by oxidative and/or glycolytic pathways.
Key Words: oxygen uptake; blood lactate concentration; power; work; intensity
2
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Introduction The acute responses of energy expenditure to different forms of resistance exercise and their underlying metabolic mechanisms have been investigated in numerous studies (Ballor et al. 1987; Beckham and Earnest 2000; Binzen et al. 2001; Wilmore et al. 1978). The physiological and metabolic responses to resistance exercise are caused by mechanical stimuli, which among other factors are determined by the external load and the contraction velocity (Toigo and Boutellier 2006). Several studies have reported the responses of oxygen uptake ( V& O 2 ), rate of energy expenditure, blood lactate concentration (LA), and excess post-exercise oxygen consumption (EPOC) to varying loads (Buitrago et al. 2012; Hunter et al. 1988; Kalb and Hunter 1991; Kang et al. 2005; Mazzetti et al. 2007; Ratamess et al. 2007; Thornton and Potteiger 2002; Willoughby et al. 1991) and contraction velocities (Ballor et al. 1987; Buitrago et al. 2012; Hunter et al. 2003; Mazzetti et al. 2007). External load and movement velocity determine the generated power and the performed work, largely determining the energy demands of exercise. The measurement of the movement velocity and the applied force enables the calculation of the generated power and the performed work during resistance exercise. Hence, several studies with different objectives have investigated the mechanical characteristics of different resistance exercises and loading schemes (Cormie et al. 2007; Harris et al. 2007; Kawamori et al. 2006; Thomas et al. 2007). For steady state/rate endurance type exercise, especially cycling and upper body exercise, the relationship between the mechanical output (e.g. power and work) and the responses of energy metabolism has been described in numerous studies (Chavarren and Calbet 1999; Francescato et al. 2003; Gaesser and Brooks 1975; Hansen et al. 1988; Kang et al. 1999). However, the measurement of mechanical variables on 3
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Page 4 of 26
resistance machines requires a more complex apparatus when compared to cycling and arm crank ergometers. Several investigations have conducted dynamometric online measurements during non isokinetic resistance exercise (Cormie et al. 2007; Harris et al. 2007; Kawamori et al. 2006; Petrella et al. 2005). Accordingly, to date, no study has specifically examined the relationship between the generated mechanical output and the corresponding elicited physiological and metabolic responses. To describe extensively the mechanical load/physiological response relationship, different resistance exercise schemes covering a wide range of external load and movement velocities have to be analysed. Furthermore, a determination and quantification of the generated mechanical output and the responses related to energy metabolism is needed Therefore, the purpose of the present investigation was to study in detail the physiological responses during and after resistance exercise as a function of the mechanical output. For the first time, a description of the relationship between the quantified, external mechanical stimuli and their associated responses of energy metabolism is expected. It was hypothesized that increases in mechanical load are attended by an elevation of the corresponding physiological and metabolic responses. The data will enable a deeper insight into of the underlying metabolism of resistance exercise, independent from the executed exercise protocol.
Materials and methods Subjects Ten healthy and resistance trained male subjects (age: 27.3 ± 3.2 years; height: 181.4 ± 4.8 cm; body mass: 81.4 ± 10.1 kg) participated in the investigation. All participants had several years of resistance training experience. The participants 4
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Page 5 of 26
were informed about content, aims and risks of the investigation and they signed an informed consent document prior to any testing. The study was performed in accordance with the declaration of Helsinki and it was approved by the Ethics Committee of the German Sport University Cologne.
Experimental Design The participants reported to the laboratory on 13 separate days between 7:00 and 10:00 a.m. after an overnight fast. Only water was allowed to be consumed ad libitum and subjects were instructed not to perform any physical activity the morning prior to testing. On day one all participants were subjected to pre testing measurements. On the other twelve days of the investigation they performed one bout of a resistance exercise on a seated chest press machine. On each testing day they lifted one out of three different external loads, 55%, 70% or 85% of one repetition maximum (1 RM), at one of four given training modes, 4-1-4-1 (4-s concentric, 1-s isometric, 4-s eccentric and 1-s isometric successive actions), 2-1-2-1 (2-s concentric, 1-s isometric, 2-s eccentric and 1-s isometric successive actions), 1-1-1-1 (1-s concentric, 1-s isometric, 1-s eccentric and 1-s isometric successive actions) or explosive (maximum velocity concentric, 1-s isometric, 1-s eccentric and 1-s isometric successive actions).
Pre-testing measurements On pre-testing day anthropometric data was obtained. Body mass and body composition were determined via a digital scale and bioelectrical impendence analysis, respectively (TANITA corp., Tokyo, Japan). Afterwards subjects were seated and were connected to an open-circuit-gas-exchange measurement system.
5
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V& O 2 and V& CO 2 were measured for 30 minutes and data was collected during the last ten minutes to calculate basal metabolic rate (BMR). Following the respiratory measurements, subjects were seated on a chest press machine (gym80 international GmbH, Gelsenkirchen, Germany). The machine settings were adjusted individually so that all subjects had the same starting and end positions during pre-testing and during the experiment. For the starting position, seat height was adjusted so that the hand grip of the machine was at the height of the sternum. The angle between shoulder blade and upper arm was 180° and the inner elbow angle was 90°. The end position was defined by complete extension of the elbow. The range of motion (ROM) was measured by a linear transducer that was placed vertically between the upper weight plate of the weight stack and the frame of the strength machine. The transducer was connected to a PC and a visual feedback system (DigiMax GmbH, Hamm, Germany) recorded and stored each subject’s range of motion, defined as the vertical displacement of the weight stack during the lifting action. Subsequently, 1RM was determined using the testing protocol suggested and described by the American College of Sports Medicine (Whaley 2005).
Experimental procedures After randomly choosing an external load and a training mode, participants were seated in the chest press machine and were connected to the open gas-exchange measurement system. Five minutes after starting the gas-exchange measurement, a blood sample from the ear lobe was collected to determine blood lactate concentration (LA) at rest. Then a brief warm up session of 15 repetitions at 30% of 1RM was performed. Thereafter, the visual feedback tracking system was activated and subjects performed a few repetitions without any external load for the purpose of 6
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Page 7 of 26
familiarization with the randomly selected training mode. The feedback system calculated and projected a tracking trace that moved according to the subjects’ range of motion and the set time for concentric, isometric and eccentric action. While executing concentric and eccentric actions, a tracking point in the display (controlled by the distance/velocity sensor) is moved up and down, respectively. By moving the tracking point at the adjusted speed the subjects followed the particularly calculated trace. The subjects were able to keep training mode constant during the complete exercise bout by using the permanent direct visual feedback. Before starting the exercise, subjects were instructed to exhale and inhale deeply during the concentric phase and eccentric phase, respectively.. During the 4-1-4-1 mode participants were instructed to conduct one complete breathing cycle (expiration and inspiration) during concentric action and during eccentric action, respectively. Ten minutes after beginning the gas-exchange measurement participants started to exercise. They were asked to maintain the effort until they failed to follow the tracking trace of the visual feedback system. In this case, participants were not able to sustain the given load and accordingly keep power constant. When exhaustion manifested this way, exercise was stopped and post exercise time started. Immediately after exercise, a capillary blood sample was taken. For a period of 30 minutes post exercise, blood sampling was repeated at intervals of two minutes. Breath-by-breath analyses were also finished 30 minutes post exercise. Fig. 1 shows the scheduled experimental protocol for one trial.
Measurements and calculations Mechanical force was measured by a dynamometer (DIGIMAX GmbH, Hamm, Germany) placed between weight stack and pull cable of the strength machine. Time 7
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Page 8 of 26
and distance were measured by the same linear transducer of the visual feedback system. The dynamometer and transducer were calibrated prior to each test. Force, distance and time were recorded at a rate of 100Hz. Mean concentric power (MCP) and total concentric work (TCW) were calculated by a specific measuring system (MECHATRONIC GmbH, Hamm, Germany). Due to the differences in the lifted mass between the subjects, the force range obtained was large. Similarly, due to the differences in range of motion between subjects for the same training modes, a wide spectrum of velocities were obtained, generating a large amount of measured values for mean concentric power and total concentric work. Respiratory gas exchange measures were assessed via an open air gas-exchange measurement system in breath-by-breath mode (ZAN 680 CPX, ZAN GmbH, Oberthulba, Germany) throughout the testing, using standard algorithms with dynamic account for the time delay between the gas consumption and volume signal. The respiratory gas exchange instrumentation was calibrated according to the manufacturer's guidelines with calibration gas. Mean V& O 2 and volume of consumed O2 were calculated during exercise as well as for the 30 minutes post-exercise. EPOC was determined by subtracting BMR averaged over 30 minutes from consumed O2 post-exercise. Blood samples were analysed for LA with an enzymaticamperometric analyser (EBIO plus, EPPENDORF AG, Hamburg, Germany). The highest LA was defined as post-exercise maximum blood lactate concentration (LAmax).
Data Analysis Data was analysed by fitting linear mixed effects models (LME) (Pinheiro and Bates 2000). The software was “R” in the latest version 2.15.0 (The R Foundation for 8
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Page 9 of 26
Statistical Computing; 2012). The “nlme” library was used for the LME functionality (Pinheiro et al. 2004). The mechanical variables mean concentric power and total concentric work served as predictors. The dependent variables were V& O 2 , O2, EPOC, and LAmax. Starting from simple linear relationships, higher order terms were added subsequently. Models were compared by likelihood statistics. When no improvement of the fit could be achieved, the simpler model was preferred, respectively. Random variation between the subjects was fundamentally modeled by assuming Gaussian distributed intercepts. Individual responses were accounted for by allowing for corresponding linear or higher order terms. Again, the simplest possible model was preferred in case of lack of improved fits.
Results
V& O 2 exhibited a linear dependency on mean concentric power (0.52 mL/W, p
