The influence of trunk mechanics on the assessment of elbow position in college aged pitchers.

Researchers have postulated that the rise in the incidence of pitching injuries is partially due to poor pitching mechanics. A topic that is often debated revolves around the correct positioning of the elbow in relationship to the body. Therefore, this study attempts to understand the associations of vertical or horizontal elbow positon with upper extremity joint moments, and ball velocity, and how elbow position is influenced by trunk position. Motion analysis data from 99 collegiate pitchers were analysed for this study. A random intercept, mixed-effects regression model was used to determine if statistically significant associations existed between elbow position and upper extremity joint moments and ball velocity. Results indicated that visual impressions of the elbow position were highly correlated with trunk position, whereas kinematic definitions of elbow position were correlated to the glenohumeral angle. Visual vertical and horizontal elbow position was associated with increased elbow varus moments (p = 0.001) and ball velocity (p = 0.019), respectively. Whereas kinematic elbow position was not associated with either upper extremity joint moments or ball velocity. Therefore, what coaches visually interpret as an improperly positioned elbow may actually be a combination of lateral lean, anterior tilt, and over rotation of the trunk.

Influence of stride length on upper extremity joint moments and ball velocity in collegiate baseball pitchers.

The initial stride down the mound is an important aspect of the baseball pitch. Understanding the implications of stride length is essential to appropriately coach baseball pitchers. The purpose of this study was to determine the association between normalised stride length and the elbow varus and glenohumeral internal rotation moments, ball velocity, trunk and pelvic rotation and forward trunk tilt. Motion analysis data collected from 99 collegiate pitchers were analysed for this study. A random intercept, mixed-effects regression model was used to determine if there were statistically significant associations between normalised stride length and the variables of interest. Secondary analyses were conducted to determine if an optimal stride length existed in this cohort. No significant associations were found between normalised stride length, ball velocity, or upper extremity joint moments. Additionally, no optimal stride length was identified; however, trends indicate that stride lengths between 131%-137% of a pitcher's leg length may be beneficial. Normalised stride length was associated with both trunk and pelvic rotation at foot contact (p < 0.001). Trunk and pelvic rotation has been previously shown to be associated with ball velocity and joint moments, indicating that stride length may have an indirect effect on ball velocity and joint moments.

Lead Foot Progression Angle in Baseball Pitchers: Implications to Ball Velocity and Upper-Extremity Joint Moments.

The instant of foot contact is an important transition point during the pitch cycle between the linear portion of the pitch, as a pitcher strides down the mound and the rotational portion of the pitch. Understanding the implications of lead foot angle at foot contact is an essential information needed to assist pitching coaches in their work with individual pitchers. Therefore, the purpose of this study was to determine the association between lead foot progression angle at foot contact and ball velocity, elbow varus moment, and pelvic rotation. Kinematic and kinetic data were collected from 99 collegiate pitchers and analyzed using a random intercept, mixed-effects regression model. Significant associations were found between lead foot progression angle at foot contact and elbow varus moment (P = .004), as well as pelvic rotation throughout the pitching motion (P < .001). The data indicate that increased lead foot internal rotation at foot contact is associated with increases in the elbow varus moment but is not associated with ball velocity. This study provides scientific evidence that the rotational positioning of the lead foot can affect both pelvic motion and upper-extremity joint moments.

Patient-Reported Outcomes, Return-to-Sport Status, and Reinjury Rates After Anterior Cruciate Ligament Reconstruction in Adolescent Athletes: Minimum 2-Year Follow-up.

BACKGROUND: Significant variation exists in the published rates of return to sport after anterior cruciate ligament (ACL) reconstruction (ACLR). Functional outcomes and psychological response to injury have been implicated as factors that influence return to sport. Most studies focus on patients aged in the mid-20s, and less is known about this topic in adolescents. PURPOSE: To report midterm ACLR results for adolescent patients with regard to return to primary sport, patient-reported outcomes, and reinjury rate. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Adolescent athletes were contacted at a minimum of 2 years after ACLR. Patients completed 2 patient-reported outcome measures, the ACL--Return to Sport After Injury (ACL-RSI) and the International Knee Documentation Committee (IKDC) subjective form, and responded to questions regarding preinjury primary sport and level of competition, post-ACLR return to primary sport status, and reinjury. RESULTS: A total of 74 patients (mean ± SD surgical age, 15.9 ± 1.5 years; follow-up age, 19.9 ± 2.0 years; response rate, 24.5%) completed the surveys at a mean of 4.0 ± 2.0 years after primary ACLR. Outcome scores averaged 90.3 ± 12.3 for IKDC and 81.6 ± 20.4 for ACL-RSI. Questionnaire responses indicated that 27.0% of patients did not return to or sustain primary sport participation after ACLR; the principal reasons were poor knee function, team/training change, and fear of another injury. Both IKDC and ACL-RSI scores were statistically lower in patients who did not successfully return to their primary sport in contrast to patients who successfully resumed their primary sport (IKDC, P = .026; ACL-RSI, P < .001). IKDC and ACL-RSI scores were moderately positively correlated with one another (r Spearman = 0.60). There were 18 patients (reinjury rate, 24.3%) who suffered another ACL injury; 8 of these injuries included ipsilateral ACL graft tear (retear rate, 10.8%). CONCLUSION: In our cohort, 73% of adolescent patients successfully returned to their primary preinjury sport at a minimum of 2 years after ACLR. Both knee function and psychological responses to injury were important in determining an adolescent athlete's return to sport. The findings support the use of the IKDC and ACL-RSI at midterm follow-up, with higher scores associated with a greater likelihood of adolescent patients returning to sport after ACLR.

The Association Among Trunk Rotation, Ball Velocity, and the Elbow Varus Moment in Collegiate-Level Baseball Pitchers.

BACKGROUND: The incidence of upper extremity injuries in baseball pitchers is increasing. Over the past decade, research has attempted to elucidate the cause of these injuries, focusing mainly on pitching arm mechanics with little examination of other important segments, such as the trunk. This is surprising, as trunk motion has been shown to have significant effects on pitching mechanics. PURPOSE: To determine the associations between trunk rotation, ball velocity, and the moments about the elbow joint. STUDY DESIGN: Descriptive laboratory study. METHODS: Data collected using 3-dimensional motion analysis techniques from 99 collegiate pitchers (18.0-24.8 years) were analyzed. A random intercept mixed-effects regression model was used to determine if significant associations existed between trunk rotation and ball velocity or elbow varus moment. RESULTS: Significant associations were found between trunk rotation angle at ball release and elbow varus moment (P = .019, ß = 0.254) as well as ball velocity (P = .016, ß = 0.060). For every 10° increase over the average trunk rotation angle at ball release, the elbow varus moment increased by 2.54 N·m and the ball velocity increased by 0.60 m/s. Additionally, the maximum rotational velocity of the trunk was positively associated with elbow varus moment (P < .001, ß = 0.029) and ball velocity (P < .001, ß = 0.007). For every 100 deg/s increase over the average maximum rotational velocity of the trunk, the elbow varus moment increased by 2.90 N·m and the ball velocity increased by 0.70 m/s. CONCLUSION: In collegiate pitchers, trunk rotation angle at ball release was significantly associated with ball velocity and elbow varus moment. Also, an increase in maximum rotational velocity of the trunk was significantly associated with an increase in the ball velocity and elbow varus moment. This work demonstrates the importance of trunk mechanics in the kinetic chain of the pitch cycle. CLINICAL RELEVANCE: Pitching coaches and trainers can use the results to stress the importance of trunk mechanics in pitching, specifically, combining adequate core function with increased trunk rotational velocity in an effort to increase pitching velocity without increasing elbow joint stress.

The mechanism of photoinduced acylation of amines by N-acyl-5,7-dinitroindoline as determined by time-resolved infrared spectroscopy.

[reaction: see text] The photochemistry of N-acyl-5,7-dinitroindoline (1) was studied in acetonitrile using nanosecond time-resolved infrared (TRIR) spectroscopy. Upon photolysis, two nearly but not completely overlapping sets of transient IR bands are observed that are assigned to two non-interconvertible conformers of mixed acetic nitronic anhydride 7. While syn-7 reverts rapidly to 1, anti-7 is long-lived and is able to acylate amines. Results of density functional theory calculations support conclusions based on experimental TRIR data.

Photoinduced carbon monoxide migration in a synthetic heme-copper complex.

Time-resolved infrared (TRIR) flash photolytic techniques have been employed to initiate and observe the efficient dissociation of CO from a synthetic heme-CO/copper complex, [((6)L)Fe(II)(CO)..Cu(I)](+) (2), in CH(3)CN and acetone at room temperature. In CH(3)CN, a significant fraction of the photodissociated CO molecules transiently bind to copper (nu(CO)(Cu) = 2091 cm(-)(1)) giving [((6)L)Fe(II)..Cu(I)(CO)](+) (4), with an observed rate constant, k(1) = 1.5 x 10(5) s(-)(1). That is followed by a slower direct transfer of CO from the copper moiety back to the heme (nu(CO)(Fe) = 1975 cm(-)(1)) with k(2) = 1600 s(-)(1). Additional transient absorption (TA) UV-vis spectroscopic experiments have been performed monitoring the CO-transfer reaction by following the Soret band. Eyring analysis of the temperature-dependent data yields DeltaH(double dagger) = 43.9 kJ mol(-)(1) for the 4-to-2 transformation, similar to that for CO dissociation from [Cu(I)(tmpa)(CO)](+) in CH(3)CN (DeltaH(double dagger) = 43.6 kJ mol(-)(1)), suggesting CO dissociation from copper regulates the binding of small molecules to the heme within [((6)L)Fe(II)..Cu(I)](+)(3). Our observations are analagous to those observed for the heme(a3)/Cu(B) active site of cytochrome c oxidase, where photodissociated CO from the heme(a3) site immediately (ps) transfers to Cu(B) followed by millisecond transfer back to the heme.

Time-resolved IR detection and study of an iminooxirane intermediate.

[reaction: see text] Iminooxirane 4 has been generated by the reaction of phenylchlorocarbene (2) with phenyl isocyanate (3) and studied by nanosecond time-resolved infrared spectroscopy. Iminooxirane 4 (1830 cm(-1)) isomerizes to alpha-lactam 5 (1880 cm(-1)) at an observed rate of 3 x 10(4) s(-1). Peak assignments were confirmed by a combination of B3LYP calculations and isotopic labeling. An acyclic transition state was found computationally for the isomerization reaction.

Photochemistry of 1-(N,N-diethylamino)diazen-1-ium-1,2-diolate: an experimental and computational investigation.

The aqueous photochemistry of the sodium salt of 1-(N,N-diethylamino)-diazen-1-ium-1,2-diolate (3) has been investigated by both experimental and computational methods. Photolysis results in the formation of the N-nitrosodiethylamine radical anion (5) and nitric oxide (NO) via a triplet excited state. The nitrosamine radical anion either undergoes electron transfer with NO before cage escape to form triplet NO(-) and nitrosamine (minor process) or rapidly dissociates to form an additional molecule of NO and ultimately amine (major process). The production of nitrosamine radical anion 5 upon photolysis of diazeniumdiolate 3 is confirmed by low-temperature EPR spectroscopy. The calculated energetics for the ground and excited states of the parent diazeniumdiolate ion at the CIS and B3LYP levels of theory as well as B3LYP calculations on the fragmentation processes were very effective in rationalizing the observed photodissociation processes.

Direct observation of an acyl nitroso species in solution by time-resolved IR spectrocopy.

Benzoyl nitroside (5) was generated in solution by laser photolysis of 3,5-diphenyl-1,2,4-oxadiazole-4-oxide (4) and studied by time-resolved infrared spectroscopy. The second-order rate constants for reaction of 5 with diethylamine and 1,3-cyclohexadiene were determined to be (1.3 +/- 0.5) x 10(5) M(-1) s(-1) and (6.0 +/- 0.5) x 10(3) M(-1) s(-1), respectively. The formation of nitroxyl (HNO), a product of the reaction of 5 with diethylamine, was also observed.