The Experts below are selected from a list of 20181 Experts worldwide ranked by ideXlab platform
Rodger Kram - One of the best experts on this subject based on the ideXlab platform.
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Do poles save energy during steep Uphill walking
European Journal of Applied Physiology, 2019Co-Authors: Nicola Giovanelli, Rodger Kram, Michele Sulli, Stefano LazzerAbstract:In trail running and in Uphill races many athletes use poles. However, there are few data about pole walking on steep Uphill. The aim of this study was to compare the energy expenditure during Uphill walking with (PW) and without (W) poles at different slopes. Fourteen mountain running athletes walked on a treadmill in two conditions (PW and W) for 5 min at seven different angles (10.1°, 15.5°, 19.8°, 25.4°, 29.8°, 35.5° and 38.9°). We measured cardiorespiratory parameters, blood lactate concentration (BLa) and rating of perceived exertion (RPE). Then, we calculated the vertical cost of transport (CoTvert). Using video analysis, we measured stride frequency (SF) and stride length (SL). Compared to W, CoTvert during PW was lower at 25.4°, 29.8° and 35.5° PW ( $$ -$$ 2.55 ± 3.97%; $$ -$$ 2.79 ± 3.88% and $$ -$$ 2.00 ± 3.41%, p
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Level, Uphill and downhill running economy values are strongly inter-correlated
European Journal of Applied Physiology, 2018Co-Authors: Timothy Joseph Breiner, Amanda Louise Ryan Ortiz, Rodger KramAbstract:Exercise economy is not solely an intrinsic physiological trait because economy in one mode of exercise (e.g., running) does not strongly correlate with economy in another mode (e.g. cycling). Economy also reflects the skill of an individual in a particular mode of exercise. Arguably, level, Uphill and downhill running constitute biomechanically different modes of exercise. Thus, we tested the hypothesis that level running economy (LRE), Uphill running economy (URE) and downhill running economy (DRE) would not be strongly inter-correlated. We measured the oxygen uptakes of 19 male trained runners during three different treadmill running speed and grade conditions: 238 m/min, 0%; 167 m/min, + 7.5%; 291 m/min, − 5%. Mean oxygen uptakes were 46.8 (SD 3.9), 48.0 (3.4) and 46.9 (3.7) ml/kg/min for level, Uphill and downhill running, respectively, indicating that the three conditions were of similar aerobic intensity. We reject our hypothesis based on the strong correlations of r = 0.909, r = 0.901 and r = 0.830, respectively, between LRE vs. URE, LRE vs. DRE and URE vs. DRE. Economical runners on level surfaces are also economical on Uphill and downhill grades. Inter-individual differences in running economy reflect differences in both intrinsic physiology and skill. Individuals who have experience with level, Uphill and downhill running appear to be equally skilled in all three modes.
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applying the cost of generating force hypothesis to Uphill running
PeerJ, 2014Co-Authors: Paolo Taboga, Wouter Hoogkamer, Rodger KramAbstract:Historically, several different approaches have been applied to explain the metabolic cost of Uphill human running. Most of these approaches result in unrealistically high values for the efficiency of performing vertical work during running Uphill, or are only valid for running up steep inclines. The purpose of this study was to reexamine the metabolic cost of Uphill running, based upon our understanding of level running energetics and ground reaction forces during Uphill running. In contrast to the vertical efficiency approach, we propose that during incline running at a certain velocity, the forces (and hence metabolic energy) required for braking and propelling the body mass parallel to the running surface are less than during level running. Based on this idea, we propose that the metabolic rate during Uphill running can be predicted by a model, which posits that (1) the metabolic cost of perpendicular bouncing remains the same as during level running, (2) the metabolic cost of running parallel to the running surface decreases with incline, (3) the delta efficiency of producing mechanical power to lift the COM vertically is constant, independent of incline and running velocity, and (4) the costs of leg and arm swing do not change with incline. To test this approach, we collected ground reaction force (GRF) data for eight runners who ran thirty 30-second trials (velocity: 2.0–3.0 m/s; incline: 0–9°). We also measured the metabolic rates of eight different runners for 17, 7-minute trials (velocity: 2.0–3.0 m/s; incline: 0–8°). During Uphill running, parallel braking GRF approached zero for the 9° incline trials. Thus, we modeled the metabolic cost of parallel running as exponentially decreasing with incline. With that assumption, best-fit parameters for the metabolic rate data indicate that the efficiency of producing mechanical power to lift the center of mass vertically was independent of incline and running velocity, with a value of ∼29%. The metabolic cost of Uphill running is not simply equal to the sum of the cost of level running and the cost of performing work to lift the body mass against gravity. Rather, it reflects a constant cost of perpendicular bouncing, decreased costs of parallel braking and propulsion and of course the cost of lifting body mass against gravity.
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advanced age and the mechanics of Uphill walking a joint level inverse dynamic analysis
Gait & Posture, 2014Co-Authors: Jason R Franz, Rodger KramAbstract:Abstract We sought to gain insight into age-related muscular limitations that may restrict the Uphill walking ability of old adults. We hypothesized that: (1) old adults would exhibit smaller peak ankle joint kinetics and larger peak hip joint kinetics than young adults during both level and Uphill walking and (2) these age-related differences in ankle and hip joint kinetics would be greatest during Uphill vs. level walking. We quantified the sagittal plane ankle, knee, and hip joint kinetics of 10 old adults (mean ± SD, age: 72 ± 5 yrs) and 8 young adults (age: 27 ± 5 yrs) walking at 1.25 m/s on a dual-belt, force-measuring treadmill at four grades (0°, +3°, +6°, +9°). As hypothesized, old adults walked with smaller peak ankle joint kinetics (e.g., power generation: −18% at +9°) and larger peak hip joint kinetics (e.g., power generation: +119% at +9°) than young adults, most evident during the late stance phase of both level and Uphill conditions. Old adults performed two to three times more single support positive work than young adults via muscles crossing the knee. In partial support of our second hypothesis, the age-related reduction in peak ankle joint moments was greater during Uphill (−0.41 Nm/kg) vs. level (−0.30 Nm/kg) walking. However, old adults that exhibited reduced propulsive ankle function during level walking could perform 44% more trailing leg positive ankle joint work to walk Uphill. Our findings indicate that maintaining ankle power generation and trailing leg propulsive function should be the primary focus of “prehabilitation” strategies for old adults to preserve their Uphill walking ability.
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how does age affect leg muscle activity coactivity during Uphill and downhill walking
Gait & Posture, 2013Co-Authors: Jason R Franz, Rodger KramAbstract:Abstract Walking Uphill and downhill can be challenging for community-dwelling old adults. We investigated the effects of age on leg muscle activity amplitudes and timing during level, Uphill, and downhill walking. We hypothesized that old adults would exhibit smaller increases in ankle extensor muscle activities and greater increases in hip extensor muscle activities compared to young adults during Uphill vs. level walking. We also hypothesized that, compared to level walking, antagonist leg muscle coactivation would be disproportionately greater in old vs. young adults during downhill walking. Ten old (72 ± 5 yrs) and ten young (25 ± 4 yrs) subjects walked at 1.25 m/s on a treadmill at seven grades (0°, ±3°, ±6°, ±9°). We quantified the stance phase electromyographic activities of the gluteus maximus (GMAX), biceps femoris (BF), rectus femoris (RF), vastus medialis (VM), medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA). Old adults exhibited smaller increases in MG activity with steeper Uphill grade than young adults (e.g., +136% vs. +174% at 9°). A disproportionate recruitment of hip muscles led to GMAX activity approaching the maximum isometric capacity of these active old adults at steep Uphill grades (e.g., old vs. young, 73% MVC vs. 33% MVC at +9°). Neither Uphill nor downhill walking affected the greater coactivation of antagonist muscles in old vs. young adults. We conclude that the disproportionate recruitment of hip muscles with advanced age may have critical implications for maintaining independent mobility in old adults, particularly at steeper Uphill grades.
Akira Saito - One of the best experts on this subject based on the ideXlab platform.
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muscle synergies are consistent across level and Uphill treadmill running
Scientific Reports, 2018Co-Authors: Akira Saito, Aya Tomita, Ryosuke Ando, Kohei Watanabe, Hiroshi AkimaAbstract:This study aimed to identify muscle synergies of the lower limb during treadmill running on level and inclined ground. Eight subjects ran on a treadmill at three speeds (2.5, 3.3, and 4.1 m/s) and two grades (level and 10% grade). Surface electromyographic (EMG) signals were recorded from 10 muscles of the lower limb, including deeper muscles such as vastus intermedius, adductor magnus, and adductor longus. Muscle synergies were extracted applying a non-negative matrix factorization algorithm, and relative co-activations across muscles and the temporal recruitment pattern were identified by muscle synergy vector and synergy activation coefficient, respectively. The scalar product between pairs of synergy vectors and synergy activation coefficients during level and Uphill running conditions were analyzed as a similarity index, with values above 0.8 recognized as similar. Approximately 4 muscle synergies controlled the majority of variability in 10 EMGs during running, and were common between level and Uphill conditions. At each running speed, inter-condition similarity was observed in synergy vector (r > 0.83) and synergy activation coefficients (r > 0.84) at each type of synergy. These results suggest that types of synergy are consistent between level and Uphill running.
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similarity of muscle synergies extracted from the lower limb including the deep muscles between level and Uphill treadmill walking
Gait & Posture, 2018Co-Authors: Akira Saito, Aya Tomita, Ryosuke Ando, Kohei Watanabe, Hiroshi AkimaAbstract:Abstract This study aimed to examine muscle synergies involving the deeper muscles of the lower limb during level and Uphill treadmill walking. Seven men and five women walked on a treadmill at three speeds (60, 80, and 100 m/min) and two grades (level and 10% grade). Surface electromyographic (EMG) signals were recorded from 10 muscles of the lower limb, including vastus intermedius, adductor magnus, and adductor longus. Muscle synergies were extracted applying non-negative matrix factorization, and the relative co-activation across muscles and the temporal information of synergy recruitment were identified by the muscle synergy vector and synergy activation coefficient, respectively. Correlation coefficients between a pair of synergy vectors during level and Uphill walking were analyzed as a similarity index, with the similarity criterion at r = 0.76. Changes in synergy activation coefficients between the walking conditions were evaluated by cross-correlation analysis. The mean number of synergies ranged from 3.8 to 4.0 across all conditions, and they were not significantly different between level and Uphill walking conditions. Similarity between walking conditions was high ( r > 0.76) for three muscle synergies, but not for one synergy that mainly consisted of the quadriceps femoris. The inter-condition similarity of the synergy activation coefficients was high for the four synergies, and a significant lag time for synergy 2 , which consisted mainly of the activity of medial gastrocnemius, was found at 60 and 80 m/min. The muscle synergies extracted from the lower limb involving the deeper muscles appear to be consistent during level and Uphill treadmill walking.
Hiroshi Akima - One of the best experts on this subject based on the ideXlab platform.
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muscle synergies are consistent across level and Uphill treadmill running
Scientific Reports, 2018Co-Authors: Akira Saito, Aya Tomita, Ryosuke Ando, Kohei Watanabe, Hiroshi AkimaAbstract:This study aimed to identify muscle synergies of the lower limb during treadmill running on level and inclined ground. Eight subjects ran on a treadmill at three speeds (2.5, 3.3, and 4.1 m/s) and two grades (level and 10% grade). Surface electromyographic (EMG) signals were recorded from 10 muscles of the lower limb, including deeper muscles such as vastus intermedius, adductor magnus, and adductor longus. Muscle synergies were extracted applying a non-negative matrix factorization algorithm, and relative co-activations across muscles and the temporal recruitment pattern were identified by muscle synergy vector and synergy activation coefficient, respectively. The scalar product between pairs of synergy vectors and synergy activation coefficients during level and Uphill running conditions were analyzed as a similarity index, with values above 0.8 recognized as similar. Approximately 4 muscle synergies controlled the majority of variability in 10 EMGs during running, and were common between level and Uphill conditions. At each running speed, inter-condition similarity was observed in synergy vector (r > 0.83) and synergy activation coefficients (r > 0.84) at each type of synergy. These results suggest that types of synergy are consistent between level and Uphill running.
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similarity of muscle synergies extracted from the lower limb including the deep muscles between level and Uphill treadmill walking
Gait & Posture, 2018Co-Authors: Akira Saito, Aya Tomita, Ryosuke Ando, Kohei Watanabe, Hiroshi AkimaAbstract:Abstract This study aimed to examine muscle synergies involving the deeper muscles of the lower limb during level and Uphill treadmill walking. Seven men and five women walked on a treadmill at three speeds (60, 80, and 100 m/min) and two grades (level and 10% grade). Surface electromyographic (EMG) signals were recorded from 10 muscles of the lower limb, including vastus intermedius, adductor magnus, and adductor longus. Muscle synergies were extracted applying non-negative matrix factorization, and the relative co-activation across muscles and the temporal information of synergy recruitment were identified by the muscle synergy vector and synergy activation coefficient, respectively. Correlation coefficients between a pair of synergy vectors during level and Uphill walking were analyzed as a similarity index, with the similarity criterion at r = 0.76. Changes in synergy activation coefficients between the walking conditions were evaluated by cross-correlation analysis. The mean number of synergies ranged from 3.8 to 4.0 across all conditions, and they were not significantly different between level and Uphill walking conditions. Similarity between walking conditions was high ( r > 0.76) for three muscle synergies, but not for one synergy that mainly consisted of the quadriceps femoris. The inter-condition similarity of the synergy activation coefficients was high for the four synergies, and a significant lag time for synergy 2 , which consisted mainly of the activity of medial gastrocnemius, was found at 60 and 80 m/min. The muscle synergies extracted from the lower limb involving the deeper muscles appear to be consistent during level and Uphill treadmill walking.
Ryosuke Ando - One of the best experts on this subject based on the ideXlab platform.
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muscle synergies are consistent across level and Uphill treadmill running
Scientific Reports, 2018Co-Authors: Akira Saito, Aya Tomita, Ryosuke Ando, Kohei Watanabe, Hiroshi AkimaAbstract:This study aimed to identify muscle synergies of the lower limb during treadmill running on level and inclined ground. Eight subjects ran on a treadmill at three speeds (2.5, 3.3, and 4.1 m/s) and two grades (level and 10% grade). Surface electromyographic (EMG) signals were recorded from 10 muscles of the lower limb, including deeper muscles such as vastus intermedius, adductor magnus, and adductor longus. Muscle synergies were extracted applying a non-negative matrix factorization algorithm, and relative co-activations across muscles and the temporal recruitment pattern were identified by muscle synergy vector and synergy activation coefficient, respectively. The scalar product between pairs of synergy vectors and synergy activation coefficients during level and Uphill running conditions were analyzed as a similarity index, with values above 0.8 recognized as similar. Approximately 4 muscle synergies controlled the majority of variability in 10 EMGs during running, and were common between level and Uphill conditions. At each running speed, inter-condition similarity was observed in synergy vector (r > 0.83) and synergy activation coefficients (r > 0.84) at each type of synergy. These results suggest that types of synergy are consistent between level and Uphill running.
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similarity of muscle synergies extracted from the lower limb including the deep muscles between level and Uphill treadmill walking
Gait & Posture, 2018Co-Authors: Akira Saito, Aya Tomita, Ryosuke Ando, Kohei Watanabe, Hiroshi AkimaAbstract:Abstract This study aimed to examine muscle synergies involving the deeper muscles of the lower limb during level and Uphill treadmill walking. Seven men and five women walked on a treadmill at three speeds (60, 80, and 100 m/min) and two grades (level and 10% grade). Surface electromyographic (EMG) signals were recorded from 10 muscles of the lower limb, including vastus intermedius, adductor magnus, and adductor longus. Muscle synergies were extracted applying non-negative matrix factorization, and the relative co-activation across muscles and the temporal information of synergy recruitment were identified by the muscle synergy vector and synergy activation coefficient, respectively. Correlation coefficients between a pair of synergy vectors during level and Uphill walking were analyzed as a similarity index, with the similarity criterion at r = 0.76. Changes in synergy activation coefficients between the walking conditions were evaluated by cross-correlation analysis. The mean number of synergies ranged from 3.8 to 4.0 across all conditions, and they were not significantly different between level and Uphill walking conditions. Similarity between walking conditions was high ( r > 0.76) for three muscle synergies, but not for one synergy that mainly consisted of the quadriceps femoris. The inter-condition similarity of the synergy activation coefficients was high for the four synergies, and a significant lag time for synergy 2 , which consisted mainly of the activity of medial gastrocnemius, was found at 60 and 80 m/min. The muscle synergies extracted from the lower limb involving the deeper muscles appear to be consistent during level and Uphill treadmill walking.
Øyvind Sandbakk - One of the best experts on this subject based on the ideXlab platform.
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Speed and heart-rate profiles in skating and classical cross-country-skiing competitions
International Journal of Sports Physiology and Performance, 2015Co-Authors: Conor M. Bolger, Jan Kocbach, Ann Magdalen Hegge, Øyvind SandbakkAbstract:Purpose: To compare the speed and heart-rate profiles during international skating and classical competitions in male and female world-class cross-country skiers. Methods: Four male and 5 female skiers performed individual time trials of 15 km (men) and 10 km (women) in the skating and classical techniques on 2 consecutive days. Races were performed on the same 5-km course. The course was mapped with GPS and a barometer to provide a valid course and elevation profile. Time, speed, and heart rate were determined for Uphill, flat, and downhill terrains throughout the entire competition by wearing a GPS and a heart-rate monitor. Results: Times in Uphill, flat, and downhill terrain were ∼55%, 15-20%, and 25-30%, respectively, of the total race time for both techniques and genders. The average speed differences between skating and classical skiing were 9% and 11% for men and women, respectively, and these values were 12% and 15% for Uphill, 8% and 13% for flat (all P < .05), and 2% and 1% for downhill terrain. The average speeds for men were 9% and 11% faster than for women in skating and classical, respectively, with corresponding numbers of 11% and 14% for Uphill, 6% and 11% for flat, and 4% and 5% for downhill terrain (all P < .05). Heart-rate profiles were relatively independent of technique and gender. Conclusion: The greatest performance differences between the skating and classical techniques and between the 2 genders were found on Uphill terrain. Therefore, these speed differences could not be explained by variations in exercise intensity.
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Analysis of a sprint ski race and associated laboratory determinants of world-class performance
European Journal of Applied Physiology, 2011Co-Authors: Øyvind Sandbakk, Stig Leirdal, Vidar Jakobsen, Gertjan Ettema, Hans-christer HolmbergAbstract:This investigation was designed to analyze the time-trial (STT) in an international cross-country skiing sprint skating competition for (1) overall STT performance and relative contributions of time spent in different sections of terrain, (2) work rate and kinematics on Uphill terrain, and (3) relationships to physiological and kinematic parameters while treadmill roller ski skating. Total time and times in nine different sections of terrain by 12 world-class male sprint skiers were determined, along with work rate and kinematics for one specific Uphill section. In addition, peak oxygen uptake (VO_2peak), gross efficiency (GE), peak speed (V_peak), and kinematics in skating were measured. Times on the last two Uphill and two final flat sections were correlated to overall STT performance ( r = ~−0.80, P
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Analysis of sprint cross-country skiing using a differential global navigation satellite system
European Journal of Applied Physiology, 2010Co-Authors: Erik Andersson, Thomas StÖggl, Øyvind Sandbakk, Billy Sperlich, Matej Supej, Hans-christer HolmbergAbstract:The purpose was to examine skiing velocities, gear choice (G2-7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (V (max)) performed using G3 skating, (2) V (max) test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO(2max) during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9-12.9 m s(-1)) and multiple transitions (21-34) between skiing gears. Skiing velocity in the Uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to Uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = -0.72, P < 0.05), and DP V (max) (r = -0.71, P < 0.05). The velocity decrease in the Uphills from lap 1 to lap 2 was correlated with VO(2max) (r = -0.78, P < 0.05). V (max) in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to Uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO(2max) was related to the ability to maintain racing velocity in the Uphills and lean body mass was related to starting velocity and DP maximal speed.
