The Relationship between Serum Relaxin Concentrations and Knee Valgus

Female athletes are at an elevated risk for tearing their anterior cruciate ligament, compared to their male counterparts. Though injury screening clinical tests and neuromuscular training programs have been widely implemented, injury rates remain high among female athletes. The purpose of this study was to examine the relationship between serum relaxin concentrations and knee valgus during three clinical tests (single leg squat, drop vertical jump, and single leg crossover dropdown). Twenty-two female athletes volunteered. Participants were scheduled for collection during the mid-luteal phase, when serum relaxin concentrations are known to be measurable. Blood samples were collected, and serum relaxin concentrations were quantified. Kinematic data were collected while participants performed the three clinical tests. Regression analyses revealed statistically significant relationships between serum relaxin concentrations and knee valgus throughout all tests. These findings suggest that serum relaxin concentrations and knee valgus are not independent of each other and more holistic approaches may be necessary to truly map out the risk for injury and ultimately reduce the rate of anterior cruciate ligament injuries. Thus, concluding that knee valgus, a highly utilized modifiable biomechanical risk factor, and relaxin, a hormone that has been associated with anterior cruciate ligament injury in female athletes, are related to each other.

Preliminary Evaluation of Dynamic Knee Valgus and Serum Relaxin Concentrations After ACL Reconstruction

Background:

Athletes who have sustained a tear of the anterior cruciate ligament (ACL) are at a greater risk of re-tear and of developing other adverse outcomes, such as knee osteoarthritis, compared with uninjured athletes. Relaxin, a peptide hormone similar in structure to insulin, has been shown to interfere with the structural integrity of the ACL in female individuals. The purpose of the present study was to evaluate dynamic knee valgus and the serum relaxin concentration (SRC) in athletes who had previously sustained a torn ACL and in those who had not.

Methods:

The study included 22 female athletes, divided into 2 groups: those who had previously sustained a torn ACL (4 participants; torn ACL in the dominant leg in all cases) and those who had not (18 participants). Kinematic data were collected at 100 Hz. To assess dynamic knee valgus, participants performed a single-leg squat, a single-leg crossover dropdown, and a drop vertical jump at 2 time points in the menstrual cycle of the patient, pre-ovulatory and mid-luteal. SRC was determined with use of the Human Relaxin-2 Immunoassay using a blood sample obtained during the mid-luteal phase of the menstrual cycle.

Results:

Independent samples t tests were utilized to compare the differences in dynamic knee valgus and SRC between groups. For the single-leg squat, participants with a prior torn ACL were found to have significantly higher dynamic knee valgus at the mid-luteal phase but not at the pre-ovulatory phase. For the drop vertical jump and single-leg crossover dropdown, participants with a prior torn ACL were found to have significantly higher dynamic knee valgus at both the pre-ovulatory and mid-luteal phases. SRC was also significantly higher among participants with a prior torn ACL.

Conclusions:

Participants who had previously sustained a torn ACL had higher SRC and more dynamic knee valgus compared with those who had not. Further investigation of the effects of hormones as a risk factor for reinjury in participants with a prior ACL tear may be worthwhile. In addition, it may be worth monitoring hormonal and biomechanical properties in athletes during the long-term recovery from ACL reconstruction.

Level of Evidence:

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

RNA-Seq and protein mass spectrometry in microdissected kidney tubules reveal signaling processes initiating lithium-induced nephrogenic diabetes insipidus

Lithium salts, used for treating bipolar disorder, frequently induce nephrogenic diabetes insipidus (NDI) thereby limiting therapeutic success. NDI is associated with loss of expression of the gene coding for the molecular water channel, aquaporin-2, in the renal collecting duct (CD). Here, we use systems biology methods in a well-established rat model of lithium-induced NDI to identify signaling pathways activated at the onset of polyuria. Using single-tubule RNA-Seq, full transcriptomes were determined in microdissected cortical collecting ducts (CCDs) of rats after 72 hours without or with initiation of lithium chloride administration. Transcriptome-wide changes in mRNA abundances were mapped to gene sets associated with curated canonical signaling pathways, showing evidence for activation of NF-κB signaling with induction of genes coding for multiple chemokines and most components of the Major Histocompatibility Complex Class I antigen-presenting complex. Administration of anti-inflammatory doses of dexamethasone to lithium chloride-treated rats countered the loss of aquaporin-2. RNA-Seq also confirmed prior evidence of a shift from quiescence into the cell cycle with arrest. Time course studies demonstrated an early (12 hour) increase in multiple immediate early response genes including several transcription factors. Protein mass spectrometry in microdissected CCDs provided corroborative evidence and identified decreased abundance of several anti-oxidant proteins. Thus, in the context of prior observations, our study can be best explained by a model in which lithium increases ERK activation leading to induction of NF-κB signaling and an inflammatory-like response that represses Aqp2 transcription.

Differences in trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes

Although polo is a well-known equestrian sport, it is fundamentally misunderstood. The purpose of this study was to examine trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes. Ten female and 17 male professional polo athletes volunteered. An electromagnetic tracking system collected kinematic data at 100 Hz while participants performed three offside forehand polo swings from a stationary wooden horse. One-way ANOVAs revealed statistically significant differences (p<0.05) in all kinematic variables and segmental velocities. Specifically, males exhibited a greater mean difference (MD=23°) of trunk flexion at take away (TA) and top of backswing (TOB)(MD=29°) trunk lateral flexion at ball contact (BC)(MD=23°), trunk rotation at TA(MD=97°) and TOB(MD=118°), shoulder abduction at TOB(MD=64°), and shoulder elevation at TOB(MD=13°) and BC(MD=40°). Females displayed greater trunk rotation at BC(MD=91°), shoulder elevation at TA(MD=19°), and elbow flexion at TA(MD=90°). Additionally, females generated greater segmental velocities early in the swing, while the males generated velocity later. The movement patterns observed amongst the males suggest energy is being transferred more efficiently along the kinetic chain, thus more efficient swing mechanics, but further investigation into the role of the trunk and lumbopelvic-hip complex in reference to the polo swing is warranted.

Upper Extremity Pain and Pitching Mechanics in National Collegiate Athletic Association (NCAA) Division I Softball

The purpose of this study was to evaluate pitching mechanics between female softball pitchers with upper extremity pain and those without upper extremity pain. Specifically, the trunk, shoulder and elbow kinematics and shoulder kinetics during the change-up softball pitch were examined. Fifty-five collegiate softball pitchers participated, divided into those with upper extremity pain (20.0±1.3 yrs.; 174.4±6.9 cm; 82.9±12.4 kg; 11.1±2.6 yrs. of experience; n=23) and those who were pain-free (19.9±1.4 yrs.; 173.8±6.9 cm; 81.4±12.5 kg; 10.0±2.5 yrs. of experience; n=32). Pitching mechanics were obtained via the trakSTAR^™ electromagnetic tracking system (Ascension Technologies, Inc., Burlington, VT, USA). Mann-Whitney U tests revealed significant differences in shoulder horizontal abduction at foot contact (p=0.014, U=153, Z=2.450) and trunk lateral flexion at ball release (p=0.012, U=150, Z=-2.515); and between shoulder distraction force at ball release (p=0.034, U=168, Z=-2.124). The pain group illustrated greater shoulder horizontal abduction at foot contact, less trunk lateral flexion towards the throwing side at ball release, and greater shoulder distraction at ball release than the pain-free group. The differences in trunk and shoulder kinematics, and shoulder kinetics between groups allows for insight into further studies examining injury pervasiveness in softball pitching.

Flow resistance along the rat renal tubule

The Reynolds number in the renal tubule is extremely low, consistent with laminar flow. Consequently, luminal flow can be described by the Hagen-Poiseuille laminar flow equation. This equation calculates the volumetric flow rate from the axial pressure gradient and flow resistance, which is dependent on the length and diameter of each renal tubule segment. Our goal was to calculate the pressure drop along each segment of the renal tubule and to determine the points of highest resistance. When the Hagen-Poiseuille equation was used for rat superficial nephrons based on known tubule flow rates, lengths, and diameters, it was found that the maximum pressure drop occurred in two segments: the thin descending limbs of Henle and the inner medullary collecting ducts. The high resistance in the thin descending limbs is due to their small diameters. The steep pressure drop observed in the inner medullary collecting ducts is due to the convergent structure of the tubules, which channels flow into fewer and fewer tubules toward the papillary tip. For short-looped nephrons, the calculated glomerular capsular pressure matched measured values, even with the high collecting duct flow rates seen in water diuresis, provided that tubule compliance was taken into account. In long-looped nephrons, the greater length of thin limb segments is likely compensated for by a larger luminal diameter. Simulation of the effect of proximal diuretics, namely acetazolamide or type 2 sodium-glucose transporter inhibitors, predicts a substantial back pressure in Bowman's capsule, which may contribute to observed decreases in glomerular filtration rate.

BIOMECHANICAL INFLUENCES OF A POSTURAL COMPRESSION GARMENT ON SCAPULAR POSITIONING

BACKGROUND

The scapula is a critical link utilized in the kinetic chain to achieve efficient overhead movement and transfer energy from the lower extremity to the upper extremity. Additionally, daily activities such as sitting at a computer or driving in a car may negatively influence an individual's ability to maintain proper body posture and therefore compromise those movements. To reduce these negative influences, posture garments have been designed to cue the individual in maintaining and improving posture and alignment, specifically targeting scapular positioning.

PURPOSE

The purpose of this study was to compare scapular positioning between an IntelliSkin™ posture-cueing compression garment and a generic performance garment on scapular kinematics during static standing.Study Design: Case control.

METHODS

Forty active females (1.68 ± 0.07 m; 67.29 ± 11.25 kg) stood in a natural standing position while wearing two different garments: IntelliSkin™ posture-cueing compression garment and a generic performance garment. Kinematic data were collected at 100 Hz using an electromagnetic tracking system (trakSTAR™, Ascension Technologies, Inc., Burlington, VT, USA) synced with The MotionMonitor^® (Innovative Sports Training, Chicago, IL., USA).

RESULTS

Repeated measures ANOVAs revealed a statistically significant Shirt by Side interaction for scapular protraction/retraction (F(1,39) = 52.91, p ≤ 0.05) and main-effect of Shirt for scapula anterior/posterior tilt (F(1,39) = 96.45, p ≤ 0.05). Individuals showed increased retraction and posterior tilt while wearing the IntelliSkin™ posture-cueing compression garment.

CONCLUSION

The results of the current study indicate that the IntelliSkin™ posture-cueing compression garment improved scapular positioning during static standing posture. The IntelliSkin™ posture-cueing compression garment may provide clinicians an adjunct strategy to include with rehabilitative protocols.

LEVEL OF EVIDENCE

Diagnosis, Level 3.

Classification of lumbopelvic-hip complex instability on kinematics amongst female team handball athletes

OBJECTIVES

The purpose of this study was to examine how lumbopelvic-hip complex (LPHC) stability, via knee valgus, affects throwing kinematics during a team handball jump shot.

DESIGN

LPHC stability was classified using the value of knee valgus at the instant of landing from the jump shot. If a participant displayed knee valgus of 17° or greater, they were classified as LPHC unstable. Stable and unstable athletes' throwing mechanics were compared.

METHODS

Twenty female team handball athletes (26.5±4.7years; 1.75±0.04m; 74.4±6.4kg; experience level: 4.8±4.1 years) participated. An electromagnetic tracking system was used to collect kinematic data while participants performed three 9-m jump shots. The variables considered were kinematics of the pelvis, trunk, and shoulder; and segmental speeds of the pelvis, torso, humeral, forearm, and ball velocities. Data were analyzed across four events: foot contact, maximum shoulder external rotation, ball release, and maximum shoulder internal rotation.

RESULTS

Statistically significant differences were found between groups in pelvis, trunk, humerus, and forearm velocities at all events (p≤0.05). Specifically, the unstable group displayed significantly slower speeds.

CONCLUSIONS

These findings suggest the difference in throwing mechanics are affected by LPHC instability for this select group of female team handball athletes. These differences infer an increased risk of injury in the upper and lower extremities when landing from a jump shot because of the energy losses throughout the kinetic chain and lack of utilization of the entire chain. It is recommended that further investigations also consider muscle activation throughout the throwing motion.