Understanding the metabolic demands of repetitive lifting tasks with different pacing strategies ... more Understanding the metabolic demands of repetitive lifting tasks with different pacing strategies may help increase productivity and prevent injuries. The purpose of this study was to determine the metabolic response of repetitive lifting tasks performed with different loads and different pacing strategies. Metabolic parameters were recorded as eight male participants (age = 24 ± 6 yr, height = 173 ± 9 cm, weight = 83 ± 23 kg) participated in predetermined pace (PP) and selfselected pace (SP) weight transfer tasks. The tasks required participants to transfer two 11.4, 15.9, and 20.5 kg weight plates individually back and forth a distance of 195.6 cm horizontally and 115.6 cm vertically (lift from 40.6 cm to 156.2 cm high). Task PP required participants to transfer the 6 weight plates each minute for 10 min (i.e., 60 total transfers); task SP required participants to make the 60 transfers in 10 min or less at a self-selected pace. Statistical analyses were made using both steady state...
Understanding the nexus between aging, physical activity, and obesity has been a source of ongoin... more Understanding the nexus between aging, physical activity, and obesity has been a source of ongoing investigation. A considerable amount of research has focused on Masters athletes in this regard, suggesting a beneficial relationship between Masters sport participation and a healthy body mass index (BMI). Some consider Active Duty military personnel as tactical athletes. As such, it is of interest to determine if aging Active Duty military personnel (or Masters Tactical Athletes) might have a similar BMI as other Masters athletes (MA). As such, this investigation examined previously recorded data of Active Duty Enlisted United States Marines (n = 402, male, 46–50 years old). The BMI of the Marines was stratified into categories of: underweight, normal, overweight, and obese. The Marines obesity prevalence was compared to US adult males (40–59 years) as well as male North American MA who competed at the 2009 Sydney World Masters Games. The Marines obesity prevalence was significantly ...
The purpose of this study was to investigate muscle activation patterns during a landing task in ... more The purpose of this study was to investigate muscle activation patterns during a landing task in boys and girls through the use of muscle synergies. Electromyographical (EMG) data from six lower extremity muscles were collected from 11 boys and 16 girls while they performed singleleg drop-landings. EMG data from six leg muscles were rectified, smoothed, and normalized to maximum dynamic muscle activity during landing. Data from 100 ms before to 100 ms after touchdown were submitted to factor analyses to extract muscle synergies along with the associated activation and weighing coefficients. Boys and girls both used three muscle synergies. The activation coefficients of these synergies captured muscle activity during the pre-landing, touchdown, and post-landing phases of the single-leg drop-landing. Analysis of the weighing coefficients indicated that within the extracted muscle synergies the girls emphasized activation of the medial hamstring muscle during the pre-landing and touchd...
The purpose of this study was to investigate associations between vertical ground reaction forces... more The purpose of this study was to investigate associations between vertical ground reaction forces and vertical barbell accelerations during the snatch. Barbell kinematic and force plate kinetic data were collected during a weightlifting competition. Time-series data were normalized to 100 % of lift phase and were entered into a pattern recognition algorithm that extracted principal patterns and calculated principal pattern scores. Significant associations indicate that a smaller, and temporally shorter, decrease in ground reaction forces during the transition phase is associated with a smaller decrease in barbell acceleration during the transition phase and a smaller peak barbell acceleration during the second pull phase. In order to optimize barbell acceleration, weighlifters may need to ensure a quick transition between the first and second pull.
Acute post activation potentiation (PAP) is a physical conditioning activity that incorporates in... more Acute post activation potentiation (PAP) is a physical conditioning activity that incorporates intense muscle activation to enhance muscular force production. Practical applications of PAP as a conditioning activity to enhance sport performance are of interest to athletes and coaches. PURPOSE: This study compared the effects of a dynamic warm-up and a dynamic warm-up followed by a PAP conditioning activity on shot put throw distance. METHODS: NCAA Division I male (n=6) and female (n=7) track and field athletes volunteered as participants for the study. The study employed a randomized repeated measures crossover design where each participant was randomly placed into one of two groups. During the first test session one group performed a dynamic warm-up followed by an 8-minute rest period then a shot put throw test. The other group performed a dynamic warm-up followed by a PAP conditioning activity comprised of 3 repetitions of a hang clean and jerk at 80% 1-RM followed by an 8-minute ...
The impact accelerations associated with heel strike in gait have been advanced as possible cause... more The impact accelerations associated with heel strike in gait have been advanced as possible causes of injury. This study examined the effectiveness of a commercial pair of polyurethane replacement insoles with respect to attenuating the accelerations experienced during heel strike. Active male subjects (n=10) age 20-30 years were instrumented with a lightweight accelerometer affixed to the distal medial aspect of the tibia. The subjects walked and ran on a motorized treadmill at 1.34, 2.68, and 3.58 m/s for the following conditions: barefoot (BF), barefoot with insole (BFI), running shoe with original insole (S), and running shoe with replacement insole (SI). Acceleration data were collected for 10 heel strikes at each of the four conditions for three treadmill speeds. Data were smoothed with a Fourier filter utilizing spectral analysis to determine appropriate cut-off frequencies. Repeated measures ANOVA revealed differences between peak impact accelerations for BF & S (p<0.05) ...
Sprint time (ST) is the product of stride length (SL) and stride rate (SR). Increases in either o... more Sprint time (ST) is the product of stride length (SL) and stride rate (SR). Increases in either of these variables results in speed improvement. Purpose: To compare resisted (RST) and assisted sprint training (AST) on sprint performance. Methods: Twenty (10 male, 10 female) collegiate sprinters and hurdlers were randomly divided into two training groups: RST (age: 21.81.8yrs, height: 1.730.10m, mass: 69.512.8kg) and AST (age: 22.22.4yrs, height: 1.760.10m, mass: 69.19.9kg). Each group trained 3 days/week for 6 weeks. The RST group used a combination of weighted sled pulls, uphill sprinting and depth jumps. The AST group combined downhill running, towing, sprint ladders and single leg bounds. Prior to and following the training interventions SL and ST (10 meter sprint time) were recorded at sprint distances of 30m, 60m, and 120m during the last 10 meters of each sprint distance. Pre-post training ST and SL were compared within training groups at each sprint distance using paired t-tests. Additionally, a gain score was calculated by taking the difference between the post and pre test scores. The gain scores for SL and ST were compared between training groups
Sprint time (ST) is the product of stride length (SL) and stride frequency (SF). Increases in eit... more Sprint time (ST) is the product of stride length (SL) and stride frequency (SF). Increases in either of these variables results in speed improvement. Purpose: To compare resisted (RST) and assisted sprint training (AST) on sprint performance. Methods: Twenty (10 male, 10 female) collegiate sprinters and hurdlers were randomly divided into two training groups: RST (age: 21.81.8yrs, height: 1.730.10m, mass: 69.512.8kg) and AST (age: 22.22.4yrs, height: 1.760.10m, mass: 69.19.9kg). Each group trained 3 days/week for 6 weeks. The RST group used a combination of weighted sled pulls, uphill sprinting and depth jumps. The AST group combined downhill running, towing, sprint ladders and single leg bounds. Prior to and following the training interventions SL and ST (10 meter sprint time) were recorded at sprint distances of 30m, 60m, and 120m during the last 10 meters of each sprint distance. Pre-post training ST and SL were compared within training groups at each sprint distance using ...
Quadriceps-to-Hamstrings Imbalances in Female Collegiate Soccer Athletes: Implication for Injury ... more Quadriceps-to-Hamstrings Imbalances in Female Collegiate Soccer Athletes: Implication for Injury Sports involving rapid jumping, repetitive stop and go movements, and sudden changes of direction place the anterior cruciate ligament (ACL) at an increased risk for injury. Female athletes tend to be quadriceps dominant suggesting a muscular imbalance between the strength of the quadriceps and hamstring thigh muscles. Ideal quadriceps-to-hamstring ratios should be as close to 1 as possible to prevent injuries in athletes; however, ratios of 1.5-1.8 are still considered normal. These Biomechanical imbalances are believed to decrease shock absorption and knee stabilization during landing. The purpose of this study was to examine the strength of the quadriceps-to-hamstrings ratios in female collegiate soccer athletes.
Since the etiology of the drift in VO2 during downhill running is unclear, this study was designe... more Since the etiology of the drift in VO2 during downhill running is unclear, this study was designed to assess the contribution of heart rate (HR), ventilation (VE), blood lactate, rectal temperature (RT), muscle damage, and several variables that have not previously been included in VO2 drift research: muscle temperature (MT), and stride rate (SR) and length (SL), to the drift in VO2. Six subjects participated in a 45-min level run (LEVEL) and two 45-min downhill runs (DOWN1 and DOWN2) at 50% VO2max. Although VO2 increased significantly over time for all bouts, the magnitude [4.3% (LEVEL), 5.4% (DOWN1), and 8.1% (DOWN2)] did not differ between bouts (P &gt; 0.05). VO2 was significantly lower during DOWN2 than during LEVEL and DOWN1 (P &lt; 0.05). MT increased during the three bouts (P &lt; 0.05) but the change over time was not different between bouts. SR and SL did not change over time within each bout nor between the two downhill runs. Muscle damage, as indicated by serum creatine kinase levels and perceived soreness, was less following LEVEL and DOWN2 than DOWN1 (P &lt; 0.05). HR and RT increased over time (P &lt; 0.05) but did not differ between bouts. VE and blood lactate did not differ over time or between bouts. VO2 drift during the three bouts paralleled changes in RT, MT, and HR but appears unrelated to muscle damage or biomechanical factors.
The purpose of this study was to identify lower extremity kinematic and kinetic patterns during w... more The purpose of this study was to identify lower extremity kinematic and kinetic patterns during weightlifting movements and to compare them across different external loads. Subjects completed multiple sets of the clean exercise at various percentage loads. Principal component analysis (PCA) was used to extract kinematic and kinetics patterns of the hip, knee, and ankle joint across the loads. These patterns were then compared across joint and percentage load. Results indicate that lower extremity kinematics and kinetics can be characterized through combinations of PCA-derived patterns. Patterns differed predominantly between joints, but not across percentage loads. The results point to joint-specific lower extremity function during Olympic weightlifting and quantified important technical aspects.
Background: Understanding the cardiovascular and psychophysical demands of repetitive lifting tas... more Background: Understanding the cardiovascular and psychophysical demands of repetitive lifting tasks is important in job design strategies. This study determined the cardiovascular (oxygen consumption (VO2) and heart rate (HR) and psychophysical response to repetitive lifting tasks in women. Methods: Ten female (age 27 ± 5 yrs) participants transferred 11.4, 15.9, and 20.5 kg weights back and forth from a rung 40.6 cm high to a rung 156.2 cm high. Rungs were 195.6 cm apart horizontally. Three, 10 minute bouts (1 = 11.4 kg; 2 = 15.9 kg; 3 = 20.5 kg) were performed at 6 lifts per minute. Cardiovascular and psychophysical (rating of perceived exertion, RPE) parameters were monitored throughout the bouts. VO2max and HRmax were determined via a maximal treadmill test. Results: VO2, HR, and RPE were significantly different between each work bout (p ＜ 0.01), with each outcome variable increasing as load increased. VO2max and HRmax equaled 46.5 ± 7.5 mLㆍkg −1 ㆍmin −1 and 191 ± 11 bpm, respectively.
Understanding the metabolic demands of repetitive lifting tasks with different pacing strategies ... more Understanding the metabolic demands of repetitive lifting tasks with different pacing strategies may help increase productivity and prevent injuries. The purpose of this study was to determine the metabolic response of repetitive lifting tasks performed with different loads and different pacing strategies. Metabolic parameters were recorded as eight male participants (age = 24 ± 6 yr, height = 173 ± 9 cm, weight = 83 ± 23 kg) participated in predetermined pace (PP) and selfselected pace (SP) weight transfer tasks. The tasks required participants to transfer two 11.4, 15.9, and 20.5 kg weight plates individually back and forth a distance of 195.6 cm horizontally and 115.6 cm vertically (lift from 40.6 cm to 156.2 cm high). Task PP required participants to transfer the 6 weight plates each minute for 10 min (i.e., 60 total transfers); task SP required participants to make the 60 transfers in 10 min or less at a self-selected pace. Statistical analyses were made using both steady state...
Understanding the nexus between aging, physical activity, and obesity has been a source of ongoin... more Understanding the nexus between aging, physical activity, and obesity has been a source of ongoing investigation. A considerable amount of research has focused on Masters athletes in this regard, suggesting a beneficial relationship between Masters sport participation and a healthy body mass index (BMI). Some consider Active Duty military personnel as tactical athletes. As such, it is of interest to determine if aging Active Duty military personnel (or Masters Tactical Athletes) might have a similar BMI as other Masters athletes (MA). As such, this investigation examined previously recorded data of Active Duty Enlisted United States Marines (n = 402, male, 46–50 years old). The BMI of the Marines was stratified into categories of: underweight, normal, overweight, and obese. The Marines obesity prevalence was compared to US adult males (40–59 years) as well as male North American MA who competed at the 2009 Sydney World Masters Games. The Marines obesity prevalence was significantly ...
The purpose of this study was to investigate muscle activation patterns during a landing task in ... more The purpose of this study was to investigate muscle activation patterns during a landing task in boys and girls through the use of muscle synergies. Electromyographical (EMG) data from six lower extremity muscles were collected from 11 boys and 16 girls while they performed singleleg drop-landings. EMG data from six leg muscles were rectified, smoothed, and normalized to maximum dynamic muscle activity during landing. Data from 100 ms before to 100 ms after touchdown were submitted to factor analyses to extract muscle synergies along with the associated activation and weighing coefficients. Boys and girls both used three muscle synergies. The activation coefficients of these synergies captured muscle activity during the pre-landing, touchdown, and post-landing phases of the single-leg drop-landing. Analysis of the weighing coefficients indicated that within the extracted muscle synergies the girls emphasized activation of the medial hamstring muscle during the pre-landing and touchd...
The purpose of this study was to investigate associations between vertical ground reaction forces... more The purpose of this study was to investigate associations between vertical ground reaction forces and vertical barbell accelerations during the snatch. Barbell kinematic and force plate kinetic data were collected during a weightlifting competition. Time-series data were normalized to 100 % of lift phase and were entered into a pattern recognition algorithm that extracted principal patterns and calculated principal pattern scores. Significant associations indicate that a smaller, and temporally shorter, decrease in ground reaction forces during the transition phase is associated with a smaller decrease in barbell acceleration during the transition phase and a smaller peak barbell acceleration during the second pull phase. In order to optimize barbell acceleration, weighlifters may need to ensure a quick transition between the first and second pull.
Acute post activation potentiation (PAP) is a physical conditioning activity that incorporates in... more Acute post activation potentiation (PAP) is a physical conditioning activity that incorporates intense muscle activation to enhance muscular force production. Practical applications of PAP as a conditioning activity to enhance sport performance are of interest to athletes and coaches. PURPOSE: This study compared the effects of a dynamic warm-up and a dynamic warm-up followed by a PAP conditioning activity on shot put throw distance. METHODS: NCAA Division I male (n=6) and female (n=7) track and field athletes volunteered as participants for the study. The study employed a randomized repeated measures crossover design where each participant was randomly placed into one of two groups. During the first test session one group performed a dynamic warm-up followed by an 8-minute rest period then a shot put throw test. The other group performed a dynamic warm-up followed by a PAP conditioning activity comprised of 3 repetitions of a hang clean and jerk at 80% 1-RM followed by an 8-minute ...
The impact accelerations associated with heel strike in gait have been advanced as possible cause... more The impact accelerations associated with heel strike in gait have been advanced as possible causes of injury. This study examined the effectiveness of a commercial pair of polyurethane replacement insoles with respect to attenuating the accelerations experienced during heel strike. Active male subjects (n=10) age 20-30 years were instrumented with a lightweight accelerometer affixed to the distal medial aspect of the tibia. The subjects walked and ran on a motorized treadmill at 1.34, 2.68, and 3.58 m/s for the following conditions: barefoot (BF), barefoot with insole (BFI), running shoe with original insole (S), and running shoe with replacement insole (SI). Acceleration data were collected for 10 heel strikes at each of the four conditions for three treadmill speeds. Data were smoothed with a Fourier filter utilizing spectral analysis to determine appropriate cut-off frequencies. Repeated measures ANOVA revealed differences between peak impact accelerations for BF & S (p<0.05) ...
Sprint time (ST) is the product of stride length (SL) and stride rate (SR). Increases in either o... more Sprint time (ST) is the product of stride length (SL) and stride rate (SR). Increases in either of these variables results in speed improvement. Purpose: To compare resisted (RST) and assisted sprint training (AST) on sprint performance. Methods: Twenty (10 male, 10 female) collegiate sprinters and hurdlers were randomly divided into two training groups: RST (age: 21.81.8yrs, height: 1.730.10m, mass: 69.512.8kg) and AST (age: 22.22.4yrs, height: 1.760.10m, mass: 69.19.9kg). Each group trained 3 days/week for 6 weeks. The RST group used a combination of weighted sled pulls, uphill sprinting and depth jumps. The AST group combined downhill running, towing, sprint ladders and single leg bounds. Prior to and following the training interventions SL and ST (10 meter sprint time) were recorded at sprint distances of 30m, 60m, and 120m during the last 10 meters of each sprint distance. Pre-post training ST and SL were compared within training groups at each sprint distance using paired t-tests. Additionally, a gain score was calculated by taking the difference between the post and pre test scores. The gain scores for SL and ST were compared between training groups
Sprint time (ST) is the product of stride length (SL) and stride frequency (SF). Increases in eit... more Sprint time (ST) is the product of stride length (SL) and stride frequency (SF). Increases in either of these variables results in speed improvement. Purpose: To compare resisted (RST) and assisted sprint training (AST) on sprint performance. Methods: Twenty (10 male, 10 female) collegiate sprinters and hurdlers were randomly divided into two training groups: RST (age: 21.81.8yrs, height: 1.730.10m, mass: 69.512.8kg) and AST (age: 22.22.4yrs, height: 1.760.10m, mass: 69.19.9kg). Each group trained 3 days/week for 6 weeks. The RST group used a combination of weighted sled pulls, uphill sprinting and depth jumps. The AST group combined downhill running, towing, sprint ladders and single leg bounds. Prior to and following the training interventions SL and ST (10 meter sprint time) were recorded at sprint distances of 30m, 60m, and 120m during the last 10 meters of each sprint distance. Pre-post training ST and SL were compared within training groups at each sprint distance using ...
Quadriceps-to-Hamstrings Imbalances in Female Collegiate Soccer Athletes: Implication for Injury ... more Quadriceps-to-Hamstrings Imbalances in Female Collegiate Soccer Athletes: Implication for Injury Sports involving rapid jumping, repetitive stop and go movements, and sudden changes of direction place the anterior cruciate ligament (ACL) at an increased risk for injury. Female athletes tend to be quadriceps dominant suggesting a muscular imbalance between the strength of the quadriceps and hamstring thigh muscles. Ideal quadriceps-to-hamstring ratios should be as close to 1 as possible to prevent injuries in athletes; however, ratios of 1.5-1.8 are still considered normal. These Biomechanical imbalances are believed to decrease shock absorption and knee stabilization during landing. The purpose of this study was to examine the strength of the quadriceps-to-hamstrings ratios in female collegiate soccer athletes.
Since the etiology of the drift in VO2 during downhill running is unclear, this study was designe... more Since the etiology of the drift in VO2 during downhill running is unclear, this study was designed to assess the contribution of heart rate (HR), ventilation (VE), blood lactate, rectal temperature (RT), muscle damage, and several variables that have not previously been included in VO2 drift research: muscle temperature (MT), and stride rate (SR) and length (SL), to the drift in VO2. Six subjects participated in a 45-min level run (LEVEL) and two 45-min downhill runs (DOWN1 and DOWN2) at 50% VO2max. Although VO2 increased significantly over time for all bouts, the magnitude [4.3% (LEVEL), 5.4% (DOWN1), and 8.1% (DOWN2)] did not differ between bouts (P &gt; 0.05). VO2 was significantly lower during DOWN2 than during LEVEL and DOWN1 (P &lt; 0.05). MT increased during the three bouts (P &lt; 0.05) but the change over time was not different between bouts. SR and SL did not change over time within each bout nor between the two downhill runs. Muscle damage, as indicated by serum creatine kinase levels and perceived soreness, was less following LEVEL and DOWN2 than DOWN1 (P &lt; 0.05). HR and RT increased over time (P &lt; 0.05) but did not differ between bouts. VE and blood lactate did not differ over time or between bouts. VO2 drift during the three bouts paralleled changes in RT, MT, and HR but appears unrelated to muscle damage or biomechanical factors.
The purpose of this study was to identify lower extremity kinematic and kinetic patterns during w... more The purpose of this study was to identify lower extremity kinematic and kinetic patterns during weightlifting movements and to compare them across different external loads. Subjects completed multiple sets of the clean exercise at various percentage loads. Principal component analysis (PCA) was used to extract kinematic and kinetics patterns of the hip, knee, and ankle joint across the loads. These patterns were then compared across joint and percentage load. Results indicate that lower extremity kinematics and kinetics can be characterized through combinations of PCA-derived patterns. Patterns differed predominantly between joints, but not across percentage loads. The results point to joint-specific lower extremity function during Olympic weightlifting and quantified important technical aspects.
Background: Understanding the cardiovascular and psychophysical demands of repetitive lifting tas... more Background: Understanding the cardiovascular and psychophysical demands of repetitive lifting tasks is important in job design strategies. This study determined the cardiovascular (oxygen consumption (VO2) and heart rate (HR) and psychophysical response to repetitive lifting tasks in women. Methods: Ten female (age 27 ± 5 yrs) participants transferred 11.4, 15.9, and 20.5 kg weights back and forth from a rung 40.6 cm high to a rung 156.2 cm high. Rungs were 195.6 cm apart horizontally. Three, 10 minute bouts (1 = 11.4 kg; 2 = 15.9 kg; 3 = 20.5 kg) were performed at 6 lifts per minute. Cardiovascular and psychophysical (rating of perceived exertion, RPE) parameters were monitored throughout the bouts. VO2max and HRmax were determined via a maximal treadmill test. Results: VO2, HR, and RPE were significantly different between each work bout (p ＜ 0.01), with each outcome variable increasing as load increased. VO2max and HRmax equaled 46.5 ± 7.5 mLㆍkg −1 ㆍmin −1 and 191 ± 11 bpm, respectively.
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