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Peter Politzer - One of the best experts on this subject based on the ideXlab platform.
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the Reaction Force constant as an indicator of synchronicity nonsynchronicity in 4 2 cycloaddition processes
Physical Chemistry Chemical Physics, 2013Co-Authors: Diana Yepes, Patricia Perez, Jane S Murray, Peter Politzer, Oscar Donosotauda, Pablo JaqueAbstract:A variety of experimental and computational analyses support the concept that a chemical Reaction has a transition region, in which the system changes from distorted states of the reactants to distorted states of the products. The boundaries of this region along the intrinsic Reaction coordinate ξ, which includes the traditional transition state, are defined unambiguously by the minimum and maximum of the Reaction Force F(ξ), which is the negative gradient of the potential energy V(ξ). The transition region is characterized by the Reaction Force constant κ(ξ), the second derivative of V(ξ), being negative throughout. It has recently been demonstrated that the profile of κ(ξ) in the transition region is a sensitive indicator of the degree of synchronicity of a concerted Reaction: a single κ(ξ) minimum is associated with full or nearly full synchronicity, while a κ(ξ) maximum (negative) between two minima is a sign of considerable nonsynchronicity, i.e. a two-stage concerted process. We have now applied Reaction Force analysis to the Diels–Alder cycloadditions of the various cyanoethylenes to cyclopentadiene. We examine the relative energy requirements of the structurally- and electronically-intensive phases of the activation processes. We demonstrate that the variation of κ(ξ) in the transition region is again indicative of the level of synchronicity. The fully synchronous cycloadditions are those in which the cyanoethylenes are symmetrically substituted. Unsymmetrical substitution leads to minor nonsynchronicity for monocyanoethylene but much more – i.e. two stages – for 1,1-dicyano- and 1,1,2-tricyanoethylene. We also show that the κ(ξ) tend to become less negative as the activation energies decrease.
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the Reaction Force constant an indicator of the synchronicity in double proton transfer Reactions
Physical Chemistry Chemical Physics, 2012Co-Authors: Diana Yepes, Jane S Murray, Peter Politzer, Pablo JaqueAbstract:Earlier work, both experimental and computational, has drawn attention to the transition region in a chemical Reaction, which includes the traditional transition state but extends along the intrinsic Reaction coordinate ξ from perturbed forms of the reactants to perturbed forms of the products. The boundaries of this region are defined by the Reaction Force F(ξ), which is the negative gradient of the potential energy V(ξ) of the system along ξ. The Reaction Force constant κ(ξ), the second derivative of V(ξ), is negative throughout the transition region. We have now demonstrated, for a series of twelve double proton transfer processes, that the profile of κ(ξ) in the transition region is an indicator of the synchronicity of the two proton migrations in each case. When they are fully or nearly fully synchronous, κ(ξ) has a single minimum in the transition region. When the migrations are considerably nonsynchronous, κ(ξ) has two minima separated by a local maximum. Such an assessment of the degree of synchronicity cannot readily be made from an examination of the transition state alone, nor it is easily detected in the profiles of V(ξ) and F(ξ).
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identification of pseudodiatomic behavior in polyatomic bond dissociation Reaction Force analysis
Journal of Chemical Physics, 2010Co-Authors: Jane S Murray, Alejandro Torolabbe, Soledad Gutierrezoliva, Peter PolitzerAbstract:An interesting uniformity that has been observed for diatomic molecular dissociation has been demonstrated to apply to many single bonds in polyatomic molecules as well. The energy to reach a key point in the bond-breaking process, at which it changes from simply stretching to transition to products, is for most cases a nearly constant fraction of the dissociation energy. The point at which this change occurs corresponds to the minimum of the Reaction Force F(R) for the dissociation, F(R) being the negative gradient of the potential energy along the Reaction coordinate. Thirty nine single bonds were analyzed at the B3PW91/6-31++G(3d,2p) level. Both adiabatic and vertical stretching were considered; those bonds for which these give essentially the same results are labeled "pseudodiatomic."
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Reaction Force analyses of nitro-aci tautomerizations of trinitromethane, the elusive trinitromethanol, picric acid and 2,4-dinitro-1H-imidazole
Theoretical Chemistry Accounts, 2009Co-Authors: Jane S Murray, Pat Lane, Michael Göbel, Thomas M. Klapötke, Peter PolitzerAbstract:We have analyzed computationally, in terms of the Reaction Force, the nitro → aci tautomerizations of trinitromethane, trinitromethanol, picric acid and 2,4-dinitro-1H-imidazole. These processes involve intramolecular transfer of a hydrogen to an NO_2 oxygen, forming the aci tautomer (a nitronic acid). The Reaction Force naturally and unambiguously divides an activation barrier into two components: (1) the energy required for initial structural changes in the reactant(s), and (2) the energy associated with the first portion of the transition to product(s). In each of these tautomerizations, the first component is dominant. For trinitromethane, it is so large that the resulting total activation barrier makes C–NO_2 bond scission energetically preferable. On the other hand, trinitromethanol—which appears to be unknown—readily undergoes fragmentation in conjunction with hydrogen transfer. Picric acid has the interesting feature that the Reaction is almost complete after the first portion of the activation process, marked by the minimum of the Reaction Force. In all four Reactions, the properties of the systems at the Force minimum, transition state and Force maximum are consistent with the concept of a “transition” region in a chemical Reaction versus simply a transition state.
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analysis of diatomic bond dissociation and formation in terms of the Reaction Force and the position dependent Reaction Force constant
Journal of Molecular Modeling, 2009Co-Authors: Jane S Murray, Alejandro Torolabbe, Peter Politzer, Timothy ClarkAbstract:Bond dissociation and formation in diatomic molecules are analyzed in terms of the Reaction Force F(R) and the Reaction Force constant κ(R). These were determined for a group of 13 molecules from their extended-Rydberg potential energy functions V(R), which are of near-experimental quality. From F(R) and κ(R) comes a two-stage description of dissociation/formation. In dissociation, the first stage involves stretching of the bond, which is opposed by an increasingly negative retarding Force F(R). This reaches a minimum and then begins to weaken in the second stage, which is the transition from stretched molecule to free atoms. Bond formation begins with the reverse transition, driven by a positive F(R) which reaches a maximum for the stretched molecule and then becomes a decreasing restoring Force. In the stages in which the system is a stretched molecule, κ(R) is positive with its maximum at the equilibrium bond length; it is zero at the minimum or maximum of F(R), and negative throughout the transition stages, going through a minimum. κ(R) <0 has been found to characterize the transition portion of a Reaction. This description of dissociation/formation is reinForced by computed B3LYP and Hartree-Fock Force constants at different atom separations for the singlet molecules. Hartree-Fock wave function stability assessments suggest that, for the single-bonded singlet molecules, the onset of electron unpairing in dissociation comes in the neighborhood of the F(R) minimum.
Jane S Murray - One of the best experts on this subject based on the ideXlab platform.
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the Reaction Force constant as an indicator of synchronicity nonsynchronicity in 4 2 cycloaddition processes
Physical Chemistry Chemical Physics, 2013Co-Authors: Diana Yepes, Patricia Perez, Jane S Murray, Peter Politzer, Oscar Donosotauda, Pablo JaqueAbstract:A variety of experimental and computational analyses support the concept that a chemical Reaction has a transition region, in which the system changes from distorted states of the reactants to distorted states of the products. The boundaries of this region along the intrinsic Reaction coordinate ξ, which includes the traditional transition state, are defined unambiguously by the minimum and maximum of the Reaction Force F(ξ), which is the negative gradient of the potential energy V(ξ). The transition region is characterized by the Reaction Force constant κ(ξ), the second derivative of V(ξ), being negative throughout. It has recently been demonstrated that the profile of κ(ξ) in the transition region is a sensitive indicator of the degree of synchronicity of a concerted Reaction: a single κ(ξ) minimum is associated with full or nearly full synchronicity, while a κ(ξ) maximum (negative) between two minima is a sign of considerable nonsynchronicity, i.e. a two-stage concerted process. We have now applied Reaction Force analysis to the Diels–Alder cycloadditions of the various cyanoethylenes to cyclopentadiene. We examine the relative energy requirements of the structurally- and electronically-intensive phases of the activation processes. We demonstrate that the variation of κ(ξ) in the transition region is again indicative of the level of synchronicity. The fully synchronous cycloadditions are those in which the cyanoethylenes are symmetrically substituted. Unsymmetrical substitution leads to minor nonsynchronicity for monocyanoethylene but much more – i.e. two stages – for 1,1-dicyano- and 1,1,2-tricyanoethylene. We also show that the κ(ξ) tend to become less negative as the activation energies decrease.
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the Reaction Force constant an indicator of the synchronicity in double proton transfer Reactions
Physical Chemistry Chemical Physics, 2012Co-Authors: Diana Yepes, Jane S Murray, Peter Politzer, Pablo JaqueAbstract:Earlier work, both experimental and computational, has drawn attention to the transition region in a chemical Reaction, which includes the traditional transition state but extends along the intrinsic Reaction coordinate ξ from perturbed forms of the reactants to perturbed forms of the products. The boundaries of this region are defined by the Reaction Force F(ξ), which is the negative gradient of the potential energy V(ξ) of the system along ξ. The Reaction Force constant κ(ξ), the second derivative of V(ξ), is negative throughout the transition region. We have now demonstrated, for a series of twelve double proton transfer processes, that the profile of κ(ξ) in the transition region is an indicator of the synchronicity of the two proton migrations in each case. When they are fully or nearly fully synchronous, κ(ξ) has a single minimum in the transition region. When the migrations are considerably nonsynchronous, κ(ξ) has two minima separated by a local maximum. Such an assessment of the degree of synchronicity cannot readily be made from an examination of the transition state alone, nor it is easily detected in the profiles of V(ξ) and F(ξ).
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identification of pseudodiatomic behavior in polyatomic bond dissociation Reaction Force analysis
Journal of Chemical Physics, 2010Co-Authors: Jane S Murray, Alejandro Torolabbe, Soledad Gutierrezoliva, Peter PolitzerAbstract:An interesting uniformity that has been observed for diatomic molecular dissociation has been demonstrated to apply to many single bonds in polyatomic molecules as well. The energy to reach a key point in the bond-breaking process, at which it changes from simply stretching to transition to products, is for most cases a nearly constant fraction of the dissociation energy. The point at which this change occurs corresponds to the minimum of the Reaction Force F(R) for the dissociation, F(R) being the negative gradient of the potential energy along the Reaction coordinate. Thirty nine single bonds were analyzed at the B3PW91/6-31++G(3d,2p) level. Both adiabatic and vertical stretching were considered; those bonds for which these give essentially the same results are labeled "pseudodiatomic."
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Reaction Force analyses of nitro-aci tautomerizations of trinitromethane, the elusive trinitromethanol, picric acid and 2,4-dinitro-1H-imidazole
Theoretical Chemistry Accounts, 2009Co-Authors: Jane S Murray, Pat Lane, Michael Göbel, Thomas M. Klapötke, Peter PolitzerAbstract:We have analyzed computationally, in terms of the Reaction Force, the nitro → aci tautomerizations of trinitromethane, trinitromethanol, picric acid and 2,4-dinitro-1H-imidazole. These processes involve intramolecular transfer of a hydrogen to an NO_2 oxygen, forming the aci tautomer (a nitronic acid). The Reaction Force naturally and unambiguously divides an activation barrier into two components: (1) the energy required for initial structural changes in the reactant(s), and (2) the energy associated with the first portion of the transition to product(s). In each of these tautomerizations, the first component is dominant. For trinitromethane, it is so large that the resulting total activation barrier makes C–NO_2 bond scission energetically preferable. On the other hand, trinitromethanol—which appears to be unknown—readily undergoes fragmentation in conjunction with hydrogen transfer. Picric acid has the interesting feature that the Reaction is almost complete after the first portion of the activation process, marked by the minimum of the Reaction Force. In all four Reactions, the properties of the systems at the Force minimum, transition state and Force maximum are consistent with the concept of a “transition” region in a chemical Reaction versus simply a transition state.
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analysis of diatomic bond dissociation and formation in terms of the Reaction Force and the position dependent Reaction Force constant
Journal of Molecular Modeling, 2009Co-Authors: Jane S Murray, Alejandro Torolabbe, Peter Politzer, Timothy ClarkAbstract:Bond dissociation and formation in diatomic molecules are analyzed in terms of the Reaction Force F(R) and the Reaction Force constant κ(R). These were determined for a group of 13 molecules from their extended-Rydberg potential energy functions V(R), which are of near-experimental quality. From F(R) and κ(R) comes a two-stage description of dissociation/formation. In dissociation, the first stage involves stretching of the bond, which is opposed by an increasingly negative retarding Force F(R). This reaches a minimum and then begins to weaken in the second stage, which is the transition from stretched molecule to free atoms. Bond formation begins with the reverse transition, driven by a positive F(R) which reaches a maximum for the stretched molecule and then becomes a decreasing restoring Force. In the stages in which the system is a stretched molecule, κ(R) is positive with its maximum at the equilibrium bond length; it is zero at the minimum or maximum of F(R), and negative throughout the transition stages, going through a minimum. κ(R) <0 has been found to characterize the transition portion of a Reaction. This description of dissociation/formation is reinForced by computed B3LYP and Hartree-Fock Force constants at different atom separations for the singlet molecules. Hartree-Fock wave function stability assessments suggest that, for the single-bonded singlet molecules, the onset of electron unpairing in dissociation comes in the neighborhood of the F(R) minimum.
Pablo Jaque - One of the best experts on this subject based on the ideXlab platform.
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Further understanding of the Ru-centered [2+2] cycloreversion/cycloaddition involved into the interconversion of ruthenacyclobutane using the Grubbs catalysts from a Reaction Force analysis
Journal of Molecular Modeling, 2019Co-Authors: Katherine Paredes-gil, Fernando Mendizábal, Pablo JaqueAbstract:The chemical reactivity of the first- and second-generation Grubbs catalysts has always been a significant issue in olefin metathesis. In the present work, we study the [2+2] cycloreversion/cycloaddition and the alkylidene rotation involved into the interconversion of the ruthenacyclobutane intermediate, through the Reaction Force and Reaction Force constant analysis. It has been found that the structural contribution controls the barrier energy in the interconversion of ruthenacyclobutane via [2+2] cycloreversion/cycloaddition, which is slightly lower in the second generation of Grubbs catalysts while its electronic contribution is slightly higher, which unveils a major rigidity and donor/acceptor properties of the NHC. This finding explains a greater structural contribution in the rate constant. Moreover, on the basis of the Reaction Force constant, the process can be classified as “two-stage”-concerted Reactions, noting a more asynchronous process when the first generation is used as a catalyst. Finally, a similar analysis into the alkylidene rotation was performed. It was determined that [2+2] cycloreversion and alkylidene rotations take place in a sequential manner, the energy barrier is again controlled by structural reorganization, and the pathway is less asynchronous.
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the Reaction Force constant as an indicator of synchronicity nonsynchronicity in 4 2 cycloaddition processes
Physical Chemistry Chemical Physics, 2013Co-Authors: Diana Yepes, Patricia Perez, Jane S Murray, Peter Politzer, Oscar Donosotauda, Pablo JaqueAbstract:A variety of experimental and computational analyses support the concept that a chemical Reaction has a transition region, in which the system changes from distorted states of the reactants to distorted states of the products. The boundaries of this region along the intrinsic Reaction coordinate ξ, which includes the traditional transition state, are defined unambiguously by the minimum and maximum of the Reaction Force F(ξ), which is the negative gradient of the potential energy V(ξ). The transition region is characterized by the Reaction Force constant κ(ξ), the second derivative of V(ξ), being negative throughout. It has recently been demonstrated that the profile of κ(ξ) in the transition region is a sensitive indicator of the degree of synchronicity of a concerted Reaction: a single κ(ξ) minimum is associated with full or nearly full synchronicity, while a κ(ξ) maximum (negative) between two minima is a sign of considerable nonsynchronicity, i.e. a two-stage concerted process. We have now applied Reaction Force analysis to the Diels–Alder cycloadditions of the various cyanoethylenes to cyclopentadiene. We examine the relative energy requirements of the structurally- and electronically-intensive phases of the activation processes. We demonstrate that the variation of κ(ξ) in the transition region is again indicative of the level of synchronicity. The fully synchronous cycloadditions are those in which the cyanoethylenes are symmetrically substituted. Unsymmetrical substitution leads to minor nonsynchronicity for monocyanoethylene but much more – i.e. two stages – for 1,1-dicyano- and 1,1,2-tricyanoethylene. We also show that the κ(ξ) tend to become less negative as the activation energies decrease.
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the Reaction Force constant an indicator of the synchronicity in double proton transfer Reactions
Physical Chemistry Chemical Physics, 2012Co-Authors: Diana Yepes, Jane S Murray, Peter Politzer, Pablo JaqueAbstract:Earlier work, both experimental and computational, has drawn attention to the transition region in a chemical Reaction, which includes the traditional transition state but extends along the intrinsic Reaction coordinate ξ from perturbed forms of the reactants to perturbed forms of the products. The boundaries of this region are defined by the Reaction Force F(ξ), which is the negative gradient of the potential energy V(ξ) of the system along ξ. The Reaction Force constant κ(ξ), the second derivative of V(ξ), is negative throughout the transition region. We have now demonstrated, for a series of twelve double proton transfer processes, that the profile of κ(ξ) in the transition region is an indicator of the synchronicity of the two proton migrations in each case. When they are fully or nearly fully synchronous, κ(ξ) has a single minimum in the transition region. When the migrations are considerably nonsynchronous, κ(ξ) has two minima separated by a local maximum. Such an assessment of the degree of synchronicity cannot readily be made from an examination of the transition state alone, nor it is easily detected in the profiles of V(ξ) and F(ξ).
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Reaction Force constant and projected Force constants of vibrational modes along the path of an intramolecular proton transfer Reaction
Chemical Physics Letters, 2008Co-Authors: Pablo Jaque, Peter Politzer, Alejandro Toro-labbé, Paul GeerlingsAbstract:Abstract We have explored the relationships between the Reaction Force F ( ξ ), the Reaction Force constant κ ( ξ ) and the projected Force constants of the intramolecular proton transfer HO−N S → O N−SH along the intrinsic Reaction coordinate ξ . The structural changes and energetics associated with the Reaction are analyzed in terms of the three regions defined by F ( ξ ): reactant, transition and product. The significance of the similarity between κ ( ξ ) and the variation of the Force constant associated to the Reaction coordinate mode, k ξ ( ξ ), is discussed in detail.
Irene S Davis - One of the best experts on this subject based on the ideXlab platform.
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a comparison of ground Reaction Force waveforms and step length between recreational endurance runners with hamstring injuries and healthy controls
Clinical Biomechanics, 2021Co-Authors: Caleb D Johnson, Irene S DavisAbstract:Abstract Background Acute hamstring injuries during sprinting have been attributed, in part, to the ground Reaction Forces experienced during early stance. However, no studies have investigated the factors associated with overuse hamstring injuries in endurance runners. Our purpose was to compare early stance ground Reaction Forces and step length between runners with overuse hamstring injuries and healthy controls. Methods 23 runners (5 men/ 18 women) who presented to a running clinic with an overuse hamstring injury were matched with healthy controls for sex, running speed and age. All participants ran on an instrumented treadmill, embedded with Force plates. A 3-min warm-up was given, at a self-selected training pace, followed by 16-s of ground Reaction Force data collection (≈20 strides). Statistical parametric mapping was used to compared ground Reaction Force waveforms. Additionally, discrete Force variables were calculated, including vertical average/instantaneous and posterior instantaneous loading rates. Mean comparisons for discrete ground Reaction Force variables and step length were performed. Findings Differences in ground Reaction Force waveforms did not reach statistical significance (p > 0.05). However, mean vertical loading rates were found to be higher in the Hamstring Injury group compared to Controls (p = 0.03–0.04) with small to moderate effect sizes (d = 0.47–0.52). No differences were found in mean step length. Interpretation These results provide evidence that vertical loading rates may be associated with overuse hamstring injuries. However, further research is needed to identify the contribution of joint kinematics/kinetics and muscle activity.
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a comparison of ground Reaction Force waveforms and step length between recreational endurance runners with hamstring injuries and healthy controls
Clinical Biomechanics, 2021Co-Authors: Caleb D Johnson, Irene S DavisAbstract:Abstract Background Acute hamstring injuries during sprinting have been attributed, in part, to the ground Reaction Forces experienced during early stance. However, no studies have investigated the factors associated with overuse hamstring injuries in endurance runners. Our purpose was to compare early stance ground Reaction Forces and step length between runners with overuse hamstring injuries and healthy controls. Methods 23 runners (5 men/ 18 women) who presented to a running clinic with an overuse hamstring injury were matched with healthy controls for sex, running speed and age. All participants ran on an instrumented treadmill, embedded with Force plates. A 3-min warm-up was given, at a self-selected training pace, followed by 16-s of ground Reaction Force data collection (≈20 strides). Statistical parametric mapping was used to compared ground Reaction Force waveforms. Additionally, discrete Force variables were calculated, including vertical average/instantaneous. Mean comparisons for discrete ground Reaction Force variables and step length were performed. Findings Differences in ground Reaction Force waveforms did not reach statistical significance (p > 0.05). However, mean vertical loading rates were found to be higher in the Hamstring Injury group compared to Controls (p = 0.03–0.04) with small to moderate effect sizes (d = 0.47–0.52). No differences were found in mean step length. Interpretation These results provide evidence that vertical loading rates may be associated with overuse hamstring injuries. However, further research is needed to identify the contribution of joint kinematics/kinetics and muscle activity.
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relationships between tibial acceleration and ground Reaction Force measures in the medial lateral and anterior posterior planes
Journal of Biomechanics, 2021Co-Authors: Caleb D Johnson, Jereme Outerleys, Irene S DavisAbstract:Abstract Peak vertical tibial accelerations during running have shown strong correlations with vertical ground Reaction Force loading rates and some associations with injury. However, little attention has been given to tibial accelerations along the medial–lateral and anterior-posterior axes. Therefore, our purpose was to examine the correlation between peak tibial accelerations and ground Reaction Force loading rates in the medial–lateral and posterior directions. Eighteen recreational runners were recruited who ran with a rearfoot strike pattern (10 men/ 8 women, mean age (yrs) = 33 ± 11). Tibial accelerations and ground Reaction Forces were collected while participants ran on an instrumented treadmill at a self-selected speed. Correlations were developed for: a) peak medial and lateral accelerations with lateral and medial loading rates, respectively, b) peak anterior tibial accelerations and posterior loading rates. Significant correlations were found between tibial accelerations and loading rates in all planes. Peak medial tibial accelerations were correlated with lateral loading rates (Rs = 0.86, p
Caleb D Johnson - One of the best experts on this subject based on the ideXlab platform.
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a comparison of ground Reaction Force waveforms and step length between recreational endurance runners with hamstring injuries and healthy controls
Clinical Biomechanics, 2021Co-Authors: Caleb D Johnson, Irene S DavisAbstract:Abstract Background Acute hamstring injuries during sprinting have been attributed, in part, to the ground Reaction Forces experienced during early stance. However, no studies have investigated the factors associated with overuse hamstring injuries in endurance runners. Our purpose was to compare early stance ground Reaction Forces and step length between runners with overuse hamstring injuries and healthy controls. Methods 23 runners (5 men/ 18 women) who presented to a running clinic with an overuse hamstring injury were matched with healthy controls for sex, running speed and age. All participants ran on an instrumented treadmill, embedded with Force plates. A 3-min warm-up was given, at a self-selected training pace, followed by 16-s of ground Reaction Force data collection (≈20 strides). Statistical parametric mapping was used to compared ground Reaction Force waveforms. Additionally, discrete Force variables were calculated, including vertical average/instantaneous and posterior instantaneous loading rates. Mean comparisons for discrete ground Reaction Force variables and step length were performed. Findings Differences in ground Reaction Force waveforms did not reach statistical significance (p > 0.05). However, mean vertical loading rates were found to be higher in the Hamstring Injury group compared to Controls (p = 0.03–0.04) with small to moderate effect sizes (d = 0.47–0.52). No differences were found in mean step length. Interpretation These results provide evidence that vertical loading rates may be associated with overuse hamstring injuries. However, further research is needed to identify the contribution of joint kinematics/kinetics and muscle activity.
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a comparison of ground Reaction Force waveforms and step length between recreational endurance runners with hamstring injuries and healthy controls
Clinical Biomechanics, 2021Co-Authors: Caleb D Johnson, Irene S DavisAbstract:Abstract Background Acute hamstring injuries during sprinting have been attributed, in part, to the ground Reaction Forces experienced during early stance. However, no studies have investigated the factors associated with overuse hamstring injuries in endurance runners. Our purpose was to compare early stance ground Reaction Forces and step length between runners with overuse hamstring injuries and healthy controls. Methods 23 runners (5 men/ 18 women) who presented to a running clinic with an overuse hamstring injury were matched with healthy controls for sex, running speed and age. All participants ran on an instrumented treadmill, embedded with Force plates. A 3-min warm-up was given, at a self-selected training pace, followed by 16-s of ground Reaction Force data collection (≈20 strides). Statistical parametric mapping was used to compared ground Reaction Force waveforms. Additionally, discrete Force variables were calculated, including vertical average/instantaneous. Mean comparisons for discrete ground Reaction Force variables and step length were performed. Findings Differences in ground Reaction Force waveforms did not reach statistical significance (p > 0.05). However, mean vertical loading rates were found to be higher in the Hamstring Injury group compared to Controls (p = 0.03–0.04) with small to moderate effect sizes (d = 0.47–0.52). No differences were found in mean step length. Interpretation These results provide evidence that vertical loading rates may be associated with overuse hamstring injuries. However, further research is needed to identify the contribution of joint kinematics/kinetics and muscle activity.
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relationships between tibial acceleration and ground Reaction Force measures in the medial lateral and anterior posterior planes
Journal of Biomechanics, 2021Co-Authors: Caleb D Johnson, Jereme Outerleys, Irene S DavisAbstract:Abstract Peak vertical tibial accelerations during running have shown strong correlations with vertical ground Reaction Force loading rates and some associations with injury. However, little attention has been given to tibial accelerations along the medial–lateral and anterior-posterior axes. Therefore, our purpose was to examine the correlation between peak tibial accelerations and ground Reaction Force loading rates in the medial–lateral and posterior directions. Eighteen recreational runners were recruited who ran with a rearfoot strike pattern (10 men/ 8 women, mean age (yrs) = 33 ± 11). Tibial accelerations and ground Reaction Forces were collected while participants ran on an instrumented treadmill at a self-selected speed. Correlations were developed for: a) peak medial and lateral accelerations with lateral and medial loading rates, respectively, b) peak anterior tibial accelerations and posterior loading rates. Significant correlations were found between tibial accelerations and loading rates in all planes. Peak medial tibial accelerations were correlated with lateral loading rates (Rs = 0.86, p
