490 Orthopedics & Biomechanics
Authors
H. de Brito Fontana, C. Ruschel, A. Haupenthal, M. Hubert, H. Roesler
Affiliation
Aquatic Biomechanics Research Laboratory, University of the State of Santa Catarina, Florianópolis, Brazil
Key words ▶ stationary sprint ● ▶ aquatic exercises ● ▶ ground reaction forces ● ▶ rehabilitation ●
Abstract
▼
This study was aimed at analyzing the cadence (Cadmax) and the peak vertical ground reaction force (Fymax) during stationary running sprint on dry land and at hip and chest level of water immersion. We hypothesized that both Fymax and Cadmax depend on the level of immersion and that differences in Cadmax between immersions do not affect Fymax during stationary sprint. 32 subjects performed the exercise at maximum cadence at each immersion level and data were collected with force plates. The results show that Cadmax and Fymax decrease 17 and 58 % from dry land to chest immersion respectively, with no
Introduction
▼ accepted after revision December 17, 2014 Bibliography DOI http://dx.doi.org/ 10.1055/s-0034-1398576 Published online: February 20, 2015 Int J Sports Med 2015; 36: 490–493 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Heiliane de Brito Fontana Aquatic Biomechanics Research Laboratory University of the State of Santa Catarina Rua Pascoal Simone 358, Coqueiros Florianópolis 88080350 Brazil Tel.: + 55/489/9162 598 Fax: + 55/483/3218 607 [email protected]
Stationary running, which consists of running on the spot with no antero-posterior displacement, is an exercise frequently used in aerobic gymnastics classes, track and field and other sports training sessions as well as rehabilitation programs. Its use is based on several objectives, such as physical conditioning and coordination training, mainly when a sufficiently large area for running is not available. In addition, this exercise has also been part of aquatic programs designed for athletes and non athletes with the intention of providing a reduction on the load required to support the body against gravity, even when maximum effort exercises are prescribed [8, 14]. When prescribing stationary running, one might be interested in the effects of running at maximum cadence, which has been called stationary sprint by practitioners. Although stationary sprint has been used as part of exercise programs in water and on land, very few studies have focused on the analysis of this exercise [1]. It is important, however, to consider the biomechanical characteristics of the exercise, such as the movement speed and the forces acting against
de Brito Fontana H et al. Ground reaction force and … Int J Sports Med 2015; 36: 490–493
effect of cadence on Fymax. While previous studies have shown similar neuromuscular responses between aquatic and on land stationary sprint, our results emphasize the differences in Fymax between environments and levels of immersion. Additionally, the characteristics of this exercise permit maximum movement speed in water to be close to the maximum speed on dry land. The valuable combination of reduced risk of orthopedic trauma with similar neuromuscular responses is provided by the stationary sprint exercise in water. The results of this study support the rationale behind the prescription of stationary sprinting in sports training sessions as well as rehabilitation programs.
the body, as well as the effects of water immersion on movement dynamics. Because water has a higher density compared to air and has an effect of buoyancy on the body, maximum movement speed is expected to be lower as the water immersion level rises. It has been shown, for example, that maximal and spontaneous (selfselected) speeds during walking are substantially reduced in water regardless of the direction of displacement – backward, forward and lateral – and gender [6]. However, since stationary running does not involve a horizontal displacement of the body, the effect of water immersion on movement speed is expected to be diminished, leading to smaller differences in cadence between environments. With regard to ground reaction forces (GRF), Fontana et al. [8] analyzed the vertical and antero-posterior peak GRF during stationary running on land and in water at 3 submaximal cadences – 90 steps/min, 110 steps/min and 130 steps/min. Although differences in vertical peak force are reported between all 3 cadences on dry land (a mean step increase of 0.15 units of body weight – BW), no differences were observed between 110 and 130 steps/min for the water
Downloaded by: Collections and Technical Services Department. Copyrighted material.
Ground Reaction Force and Cadence during Stationary Running Sprint in Water and on Land
running exercise (step increase of 0.03 and 0.05 BW at chest and hip immersion respectively). All cadences analyzed by Fontana et al. [8] were based on preset conditions that could be easily matched between environments and thus the intensity of the vertical peak GRF during stationary running at maximum cadence at each level of immersion is not known. Therefore, the aim of this study was to analyze the cadence and the vertical peak GRF during stationary running at maximum effort on dry land, at hip and chest levels of water immersion. Our hypotheses were i) that both the vertical ground reaction force and the movement cadence during stationary sprint depend on the level of immersion and ii) that differences in movement cadence between immersions are too small to affect the vertical ground reaction force during stationary sprint.
Materials and Methods
▼
32 students (16 male, 16 female) from the Physical Education program at the University of the State of Santa Catarina, who volunteered in response to an advertisement, participated in this study. Mean (SD) age, height, and mass for the subjects were 25 (4.0) years, 1.72 (0.09) m, and 70.7 (12.7) kg, respectively. Subjects were selected according to the following criteria: percentage of body fat (between 12 and 16 % for men and 20 and 25 % for women [17]); being active in sports such as swimming, soccer, volleyball, or track and field; and being familiar with aquatic exercises and able to swim. Subjects were excluded if they had suffered any injury or had undergone any surgery in the previous 2 years. The subjects provided informed written consent to participate in the study which meets the ethical standards proposed by Harriss and Atkinson [9]. The test consisted of stationary running at maximum speed with 3 different immersion conditions – immersed to the chest; immersed to the hip; and no immersion (dry land). Chest and hip levels of immersion corresponded to the height of subject's xiphoid process and iliac crest, respectively. Data for the vertical component of the GRF were collected (1 000 Hz) with 2 force plates [4] (dimensions 400 × 400 × 100 mm, sensitivity of 2 N, 300 Hz of natural frequency and an error of less than 1 %), one placed at the bottom of a swimming pool and another on dry land. The data acquisition system included a signal conditioner, an A/D convertor and a signal analysis and editing software (ADS2000-IP and AqDados 7.02, Lynx Tecnologia Eletrônica, São Paulo, Brazil). Anthropometric data were acquired as follows: (a) body mass of the subjects using an electronic scale (model MEA- 08128; Plenna Especialidades LTDA, São Paulo, Brazil; scale of 0.1 kg), (b) height of the subjects using a stadiometer (Sanny American Medical do Brasil LTDA, São Bernardo do Campo, Brazil; scale of 0.01 m), and (c) subjects’ cutaneous folds using a scientific caliper (CESCORF Equipamentos Antropométricos LTDA, Porto Alegre, Brazil; scale of 0.1 mm). Percentage of body fat was determined through the calculation of subjects’ body density [19]. For the male subjects, body density was calculated via a regression equation using the sum of the chest, abdominal, and thigh skin folds [11]. For women, the regression equation used the sum of the triceps, suprailiac, and thigh skin folds [12]. After the anthropometric measurements, the stationary running exercise was demonstrated and subjects performed it first on land and then in water with chest and hip immersion conditions randomized. The force plate was adjusted at the bottom of the
swimming pool according to the height of the anatomical structures used as references for the immersion levels (xiphoid process for chest level and iliac crest for hip levels). At each condition, a 5-min warm up consisting of stationary running at a submaximal speed was completed prior to data collection. Subjects were then instructed to perform the stationary running exercise for 15 s at maximum cadence. Verbal encouragement was provided to subjects during trials. Trials were considered valid when the subjects touched the force platform with only 1 foot at a time (reflective of a flight phase) and without looking down. In addition, participants were asked to perform the exercise with a hip flexion of approximately 90 °. A practitioner with 5 years of experience in exercise prescription was responsible for ensuring proper running sprint motion. All subjects reached one valid trial with 1 or 2 attempts. Force and cadence measurements were considered reliable based on the results of a pilot study using the same procedures described above (ICCs at land, hip and chest conditions respectively were, for the peak vertical GRF, 0.91, 0.97, and 0.73 and, for the maximum cadence, 0.71, 0.76, and 0.75). All GRF data were exported and analyzed using Scilab 4.1.2 software, (Institut National de Recherche en Informatique et en Automatique, Rocquencourt, France). Data were low pass filtered at 20 Hz using a 3rd order recursive Butterworth filter. Data were then normalized to the subject’s body weight (BW) measured outside the water. 30 steps were then selected from each subject for analysis, and the vertical peak GRF (Fymax) was identified. Running cadence (Cadmax) was analyzed through a Fast Fourier Transform (FFT). Using a FFT algorithm, the main frequency of signals was analyzed. This frequency represents the number of steps in the force platform per second (Hz). In order to facilitate data interpretation, movement cadence in Hz was converted to steps/minute. SPSS Version 17.0 software (SPSS Inc, Chicago, USA) with α = 0.05 was used to analyze the data. Means and standard deviations were calculated for Fymax and Cadmax for each level of immersion. One factor repeated measures ANOVA was used to analyze the effect of immersion level on Cadmax and ANCOVA with Cadmax as a covariate was used to test differences on Fymax between levels of immersion. Effect sizes were estimated through partial eta-squared (η2).
Results
▼
The maximum cadence (Cadmax) reached by subjects during stationary running on land and at hip and chest immersion is shown in ● ▶ Fig. 1. As expected, movement cadence decreased statistically with increasing immersion level from dry land to chest immersion (partial η2 = 0.797). The intensity of the vertical peak GRF (Fymax) during stationary running at maximum effort at each immersion condition is shown in ● ▶ Fig. 2. Similarly to Cadmax, Fymax also decreased with increasing immersion level (partial η2 = 0.952). and was statistically different among the 3 conditions analyzed in this study. Despite the difference, no statistically significant effect of Cadmax on Fymax was observed (F = 0.099, p = 0.754).
Discussion
▼
In this study we investigated the cadence and the vertical peak GRF during stationary running at maximum effort on dry land
de Brito Fontana H et al. Ground reaction force and … Int J Sports Med 2015; 36: 490–493
Downloaded by: Collections and Technical Services Department. Copyrighted material.
Orthopedics & Biomechanics 491
and at hip and chest levels of immersion. Knowledge regarding the intensity of the vertical peak GRF and movement cadence during stationary sprint in water and on land is required to substantiate decision-making when prescribing this exercise. The results show that movement cadence and vertical peak GRF decrease, respectively, 17 and 58 % from dry land to chest immersion. Despite the differences on movement cadence between immersion conditions, no effect of cadence on the vertical peak GRF during stationary running at maximum effort was observed. Running in water is a popular mode of aerobic training [1, 7, 14]. One of the effects of the physical properties of water is that exercises performed in water need to overcome a more intense resistance. The water is approximately 800 times denser than air [18] which leads to an equivalent increase in drag force. Besides the fluid density, the intensity of the drag force depends on other factors such as the frontal area of the body/segment that is moving against water resistance and the speed of movement. If
Cadmax 350
CADENCE (steps/min)
300
275 ± 20
250
235 ± 19
227 ± 21
HIP IMMERSION
CHEST IMMERSION
200 150 100 50 0
DRY LAND
Fig. 1 Mean ± 1 SD of maximum cadence (Cadmax) during stationary running at hip and chest water immersion level and on dry land. ≠ symbols indicate statistically significant differences at ANOVA with Bonferroni multiple comparisons (p
Authors
H. de Brito Fontana, C. Ruschel, A. Haupenthal, M. Hubert, H. Roesler
Affiliation
Aquatic Biomechanics Research Laboratory, University of the State of Santa Catarina, Florianópolis, Brazil
Key words ▶ stationary sprint ● ▶ aquatic exercises ● ▶ ground reaction forces ● ▶ rehabilitation ●
Abstract
▼
This study was aimed at analyzing the cadence (Cadmax) and the peak vertical ground reaction force (Fymax) during stationary running sprint on dry land and at hip and chest level of water immersion. We hypothesized that both Fymax and Cadmax depend on the level of immersion and that differences in Cadmax between immersions do not affect Fymax during stationary sprint. 32 subjects performed the exercise at maximum cadence at each immersion level and data were collected with force plates. The results show that Cadmax and Fymax decrease 17 and 58 % from dry land to chest immersion respectively, with no
Introduction
▼ accepted after revision December 17, 2014 Bibliography DOI http://dx.doi.org/ 10.1055/s-0034-1398576 Published online: February 20, 2015 Int J Sports Med 2015; 36: 490–493 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Heiliane de Brito Fontana Aquatic Biomechanics Research Laboratory University of the State of Santa Catarina Rua Pascoal Simone 358, Coqueiros Florianópolis 88080350 Brazil Tel.: + 55/489/9162 598 Fax: + 55/483/3218 607 [email protected]
Stationary running, which consists of running on the spot with no antero-posterior displacement, is an exercise frequently used in aerobic gymnastics classes, track and field and other sports training sessions as well as rehabilitation programs. Its use is based on several objectives, such as physical conditioning and coordination training, mainly when a sufficiently large area for running is not available. In addition, this exercise has also been part of aquatic programs designed for athletes and non athletes with the intention of providing a reduction on the load required to support the body against gravity, even when maximum effort exercises are prescribed [8, 14]. When prescribing stationary running, one might be interested in the effects of running at maximum cadence, which has been called stationary sprint by practitioners. Although stationary sprint has been used as part of exercise programs in water and on land, very few studies have focused on the analysis of this exercise [1]. It is important, however, to consider the biomechanical characteristics of the exercise, such as the movement speed and the forces acting against
de Brito Fontana H et al. Ground reaction force and … Int J Sports Med 2015; 36: 490–493
effect of cadence on Fymax. While previous studies have shown similar neuromuscular responses between aquatic and on land stationary sprint, our results emphasize the differences in Fymax between environments and levels of immersion. Additionally, the characteristics of this exercise permit maximum movement speed in water to be close to the maximum speed on dry land. The valuable combination of reduced risk of orthopedic trauma with similar neuromuscular responses is provided by the stationary sprint exercise in water. The results of this study support the rationale behind the prescription of stationary sprinting in sports training sessions as well as rehabilitation programs.
the body, as well as the effects of water immersion on movement dynamics. Because water has a higher density compared to air and has an effect of buoyancy on the body, maximum movement speed is expected to be lower as the water immersion level rises. It has been shown, for example, that maximal and spontaneous (selfselected) speeds during walking are substantially reduced in water regardless of the direction of displacement – backward, forward and lateral – and gender [6]. However, since stationary running does not involve a horizontal displacement of the body, the effect of water immersion on movement speed is expected to be diminished, leading to smaller differences in cadence between environments. With regard to ground reaction forces (GRF), Fontana et al. [8] analyzed the vertical and antero-posterior peak GRF during stationary running on land and in water at 3 submaximal cadences – 90 steps/min, 110 steps/min and 130 steps/min. Although differences in vertical peak force are reported between all 3 cadences on dry land (a mean step increase of 0.15 units of body weight – BW), no differences were observed between 110 and 130 steps/min for the water
Downloaded by: Collections and Technical Services Department. Copyrighted material.
Ground Reaction Force and Cadence during Stationary Running Sprint in Water and on Land
running exercise (step increase of 0.03 and 0.05 BW at chest and hip immersion respectively). All cadences analyzed by Fontana et al. [8] were based on preset conditions that could be easily matched between environments and thus the intensity of the vertical peak GRF during stationary running at maximum cadence at each level of immersion is not known. Therefore, the aim of this study was to analyze the cadence and the vertical peak GRF during stationary running at maximum effort on dry land, at hip and chest levels of water immersion. Our hypotheses were i) that both the vertical ground reaction force and the movement cadence during stationary sprint depend on the level of immersion and ii) that differences in movement cadence between immersions are too small to affect the vertical ground reaction force during stationary sprint.
Materials and Methods
▼
32 students (16 male, 16 female) from the Physical Education program at the University of the State of Santa Catarina, who volunteered in response to an advertisement, participated in this study. Mean (SD) age, height, and mass for the subjects were 25 (4.0) years, 1.72 (0.09) m, and 70.7 (12.7) kg, respectively. Subjects were selected according to the following criteria: percentage of body fat (between 12 and 16 % for men and 20 and 25 % for women [17]); being active in sports such as swimming, soccer, volleyball, or track and field; and being familiar with aquatic exercises and able to swim. Subjects were excluded if they had suffered any injury or had undergone any surgery in the previous 2 years. The subjects provided informed written consent to participate in the study which meets the ethical standards proposed by Harriss and Atkinson [9]. The test consisted of stationary running at maximum speed with 3 different immersion conditions – immersed to the chest; immersed to the hip; and no immersion (dry land). Chest and hip levels of immersion corresponded to the height of subject's xiphoid process and iliac crest, respectively. Data for the vertical component of the GRF were collected (1 000 Hz) with 2 force plates [4] (dimensions 400 × 400 × 100 mm, sensitivity of 2 N, 300 Hz of natural frequency and an error of less than 1 %), one placed at the bottom of a swimming pool and another on dry land. The data acquisition system included a signal conditioner, an A/D convertor and a signal analysis and editing software (ADS2000-IP and AqDados 7.02, Lynx Tecnologia Eletrônica, São Paulo, Brazil). Anthropometric data were acquired as follows: (a) body mass of the subjects using an electronic scale (model MEA- 08128; Plenna Especialidades LTDA, São Paulo, Brazil; scale of 0.1 kg), (b) height of the subjects using a stadiometer (Sanny American Medical do Brasil LTDA, São Bernardo do Campo, Brazil; scale of 0.01 m), and (c) subjects’ cutaneous folds using a scientific caliper (CESCORF Equipamentos Antropométricos LTDA, Porto Alegre, Brazil; scale of 0.1 mm). Percentage of body fat was determined through the calculation of subjects’ body density [19]. For the male subjects, body density was calculated via a regression equation using the sum of the chest, abdominal, and thigh skin folds [11]. For women, the regression equation used the sum of the triceps, suprailiac, and thigh skin folds [12]. After the anthropometric measurements, the stationary running exercise was demonstrated and subjects performed it first on land and then in water with chest and hip immersion conditions randomized. The force plate was adjusted at the bottom of the
swimming pool according to the height of the anatomical structures used as references for the immersion levels (xiphoid process for chest level and iliac crest for hip levels). At each condition, a 5-min warm up consisting of stationary running at a submaximal speed was completed prior to data collection. Subjects were then instructed to perform the stationary running exercise for 15 s at maximum cadence. Verbal encouragement was provided to subjects during trials. Trials were considered valid when the subjects touched the force platform with only 1 foot at a time (reflective of a flight phase) and without looking down. In addition, participants were asked to perform the exercise with a hip flexion of approximately 90 °. A practitioner with 5 years of experience in exercise prescription was responsible for ensuring proper running sprint motion. All subjects reached one valid trial with 1 or 2 attempts. Force and cadence measurements were considered reliable based on the results of a pilot study using the same procedures described above (ICCs at land, hip and chest conditions respectively were, for the peak vertical GRF, 0.91, 0.97, and 0.73 and, for the maximum cadence, 0.71, 0.76, and 0.75). All GRF data were exported and analyzed using Scilab 4.1.2 software, (Institut National de Recherche en Informatique et en Automatique, Rocquencourt, France). Data were low pass filtered at 20 Hz using a 3rd order recursive Butterworth filter. Data were then normalized to the subject’s body weight (BW) measured outside the water. 30 steps were then selected from each subject for analysis, and the vertical peak GRF (Fymax) was identified. Running cadence (Cadmax) was analyzed through a Fast Fourier Transform (FFT). Using a FFT algorithm, the main frequency of signals was analyzed. This frequency represents the number of steps in the force platform per second (Hz). In order to facilitate data interpretation, movement cadence in Hz was converted to steps/minute. SPSS Version 17.0 software (SPSS Inc, Chicago, USA) with α = 0.05 was used to analyze the data. Means and standard deviations were calculated for Fymax and Cadmax for each level of immersion. One factor repeated measures ANOVA was used to analyze the effect of immersion level on Cadmax and ANCOVA with Cadmax as a covariate was used to test differences on Fymax between levels of immersion. Effect sizes were estimated through partial eta-squared (η2).
Results
▼
The maximum cadence (Cadmax) reached by subjects during stationary running on land and at hip and chest immersion is shown in ● ▶ Fig. 1. As expected, movement cadence decreased statistically with increasing immersion level from dry land to chest immersion (partial η2 = 0.797). The intensity of the vertical peak GRF (Fymax) during stationary running at maximum effort at each immersion condition is shown in ● ▶ Fig. 2. Similarly to Cadmax, Fymax also decreased with increasing immersion level (partial η2 = 0.952). and was statistically different among the 3 conditions analyzed in this study. Despite the difference, no statistically significant effect of Cadmax on Fymax was observed (F = 0.099, p = 0.754).
Discussion
▼
In this study we investigated the cadence and the vertical peak GRF during stationary running at maximum effort on dry land
de Brito Fontana H et al. Ground reaction force and … Int J Sports Med 2015; 36: 490–493
Downloaded by: Collections and Technical Services Department. Copyrighted material.
Orthopedics & Biomechanics 491
and at hip and chest levels of immersion. Knowledge regarding the intensity of the vertical peak GRF and movement cadence during stationary sprint in water and on land is required to substantiate decision-making when prescribing this exercise. The results show that movement cadence and vertical peak GRF decrease, respectively, 17 and 58 % from dry land to chest immersion. Despite the differences on movement cadence between immersion conditions, no effect of cadence on the vertical peak GRF during stationary running at maximum effort was observed. Running in water is a popular mode of aerobic training [1, 7, 14]. One of the effects of the physical properties of water is that exercises performed in water need to overcome a more intense resistance. The water is approximately 800 times denser than air [18] which leads to an equivalent increase in drag force. Besides the fluid density, the intensity of the drag force depends on other factors such as the frontal area of the body/segment that is moving against water resistance and the speed of movement. If
Cadmax 350
CADENCE (steps/min)
300
275 ± 20
250
235 ± 19
227 ± 21
HIP IMMERSION
CHEST IMMERSION
200 150 100 50 0
DRY LAND
Fig. 1 Mean ± 1 SD of maximum cadence (Cadmax) during stationary running at hip and chest water immersion level and on dry land. ≠ symbols indicate statistically significant differences at ANOVA with Bonferroni multiple comparisons (p
