Hope C. Davis

Exercise augments the nocturnal prolactin rise in exercise-trained men

Objective: The objective of this study was to profile over a 24 h period the prolactin responses of exercise-trained men on a day involving rest with no exercise in comparison to a day involving exercise training sessions. Methods: This is a quasi-experimental design study using repeated measures determination of 24 h prolactin responses in exercise-trained men (n = 16; age = 27.3± 3.3 years (mean ± standard deviation)). Blood samples were taken hourly over a 24 h period on a day involving two intensive exercise training sessions (ED), and on a separate control day (CD) with no exercise activity. The order of the ED and CD was randomized. Physical activity and diet were controlled and replicated for the ED and CD. Blood specimens were handled, prepared and analyzed utilizing appropriate standard clinical practices. The data were analyzed with the Friedman analysis of variance and Nemenyi post hoc statistical procedure for repeated measures. Results: On the CD, prolactin displayed a typical circadian rhythm with daytime values of the hormone being less than the nocturnal rise once sleep had begun (p < 0.05; 16:00–20:00 h > all other times). On the ED, prolactin responses were noticeably different from those of the CD. The morning and afternoon exercise sessions included significant increases in prolactin immediately at the end of the exercise sessions, being greater than corresponding CD time points (p < 0.01; 01:00 h and 10:00 h); also for the second hour (2 h) following the morning exercise session. On the ED there was a displayed circadian nocturnal response in the hormone with 16:00–24:00 h being elevated above the all nonexercise effected values for that specific day (p < 0.01). Finally, the ED nocturnal elevation for prolactin for 16:00–24:00 h was significantly greater than the same respective hours on the CD (p < 0.05). Conclusion: Findings clearly demonstrated that nocturnal prolactin responses are augmented in exercise-trained men on days when they perform exercise. The mechanisms inducing this adaptive response are unclear but warrant further investigation.

Growth Hormone-Insulin-Like Growth Factor Axis, Thyroid Axis, Prolactin, and Exercise

This chapter addresses what is known about the endocrine system components growth hormone (GH)-insulin-like growth factor (IGF) axis, thyroid axis, and prolactin relative to exercise and exercise training. Each one of these hormone axes contributes to the maintenance of homeostasis in the body through impact on a multitude of physiological systems. The homeostatic disruption of exercise causes differing responses in each hormone axis. GH levels increase with sufficient stimulation, and IGFs are released in response to GH from the anterior pituitary providing multiple roles including anabolic properties. Changes in the thyroid hormones T3 and T4 vary greatly with exercise, from increases/decreases to no change in levels across different exercise types, intensities and durations. These ambiguous findings could be due to numerous confounding factors (e.g. nutrition status) within the research. Prolactin increases proportionally to the intensity of the exercise. The magnitude may be augmented with extended durations; conflicting findings have been reported with resistance training. While the responses to exercise vary, it appears there may be overall adaptive and regenerative impacts on the body into recovery by these hormones through immune and tissue inflammatory responses/mediations. Nonetheless, well-designed exercise research studies are still needed on each of these hormones, especially thyroid hormones and prolactin.

Time between anterior cruciate ligament injury and reconstruction and cartilage metabolism six-months following reconstruction

BACKGROUND To determine the association between time from injury to ACL reconstruction (TimeInjury-ACLR) and biochemical markers of cartilage metabolism and inflammation six months following ACL reconstruction (ACLR). METHODS Individuals with a unilateral ACL injury were enrolled at initial presentation in the orthopedic clinic; blood was collected six months following ACLR. Enzyme-linked immunosorbent assays were used to analyze the ratio of serum concentrations of type-II collagen breakdown (C2C) to synthesis (CPII), plasma matrix metalloproteinase-3 (MMP-3), interleukin-6 (IL-6), and serum aggrecan neoepitope (ARGS). We used separate linear regressions to assess associations between biochemical markers and TimeInjury-ACLR. RESULTS Twenty-two participants (50% females, mean [SD], age 21.9 [4.5] years old; BMI 23.8 [2.6] kg/m2) completed the study. TimeInjury-ACLR ranged from nine to 67days (31.0 [14.4days]). Greater TimeInjury-ACLR predicted greater serum C2C:CPII ratios six months following ACLR (C2C:CPII=0.15 [0.02], R2=0.213, P=0.030). Males (R2=0.733, P=0.001) but not females (R2=0.030, P=0.609) demonstrated a significant association between greater C2C:CPII and TimeInjury-ACLR at the six-month follow-up exam. TimeInjury-ACLR did not associate with IL-6, MMP-3, or ARGS at six months. CONCLUSIONS Greater time between injury and ACL reconstruction was associated with greater serum C2C:CPII six months following ACLR in males but not females, and IL-6, MMP-3, and ARGS levels were not associated with TimeInjury-ACLR in males or females. The time between ACL injury and ACLR may affect collagen metabolism in males and should be further investigated in a larger study along with other patient-relevant outcomes.

Walking gait asymmetries 6 months following anterior cruciate ligament reconstruction predict 12-month patient-reported outcomes: GAIT AND OUTCOMES POST-ACLR

The study sought to determine the association between gait biomechanics (vertical ground reaction force [vGRF], vGRF loading rate [vGRF‐LR]) collected 6 months following anterior cruciate ligament reconstruction (ACLR) with patient‐reported outcomes at 12 months following ACLR. Walking gait biomechanics and all subsections of the Knee Injury and Osteoarthritis Outcomes Score (KOOS) were collected at 6 and 12 months following ACLR, respectively, in 25 individuals with a unilateral ACLR. Peak vGRF and peak instantaneous vGRF‐LR were extracted from the first 50% of the stance phase. Limb symmetry indices (LSI) were used to normalize outcomes in the ACLR limb to that of the uninjured limb (ACLR/uninjured). Linear regression analyses were used to determine associations between biomechanical outcomes and KOOS while accounting for walking speed. Receiver operator characteristic curves were used to determine the accuracy of 6‐month biomechanical outcomes for identifying individuals with acceptable patient‐reported outcomes, using previously defined KOOS cut‐off scores, 12 months post‐ACLR. Individuals with lower peak vGRF LSI 6 months post‐ACLR demonstrated worse patient‐reported outcomes (KOOS Pain, Activities of Daily life, Sport and Recreation, Quality of Life) at the 12‐month exam. A peak vGRF LSI ≥0.99 6 months following ACLR associated with 13.33× higher odds of reporting acceptable patient‐reported outcomes 12 months post‐ACLR. Lesser peak vGRF LSI during walking at 6‐months post‐ACLR may be a critical indicator of worse future patient‐reported outcomes. Clinical significance achieving early symmetrical lower extremity loading and minimizing under‐loading of the ACLR limb during walking may be a potential therapeutic target for improving patient‐reported outcomes post‐ACLR.

Quadriceps Rate of Torque Development and Disability in Persons With Tibiofemoral Osteoarthritis

• BACKGROUND: Declines in the ability to rapidly generate quadriceps muscle torque may underlie disability in individuals with tibiofemoral osteoarthritis. • OBJECTIVE: To determine whether quadriceps rate of torque development (RTD) predicts self‐reported disability and physical performance outcomes in individuals with tibiofemoral osteoarthritis. • METHODS: This controlled laboratory, cross‐sectional study assessed quadriceps strength and RTD in 76 individuals (55% female; mean ± SD age, 61.83 ± 7.11 years) with symptomatic and radiographic tibiofemoral osteoarthritis. Early (0‐50 milliseconds), late (100‐200 milliseconds), and overall peak RTDs were quantified in the symptomatic (involved) and contralateral limbs and used to calculate bilateral average values. Disability was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function subscale and 3 physical performance tests, including the (1) 20‐m fast‐paced walk, (2) 30‐second chair stand, and (3) timed stair climb. Separate univariate regression models were used to determine the unique associations among measures of quadriceps RTD, WOMAC function score, and physical performance outcomes after accounting for quadriceps strength (change in R2). • RESULTS: Greater involved‐side late RTD and greater bilateral average early RTD were associated with faster walking (change in R2 = 0.05, P = .013 and change in R2 = 0.05, P = .043, respectively). Greater bilateral average late RTD was associated with faster walking (change in R2 = 0.20, P<.001) and faster stair climb (change in R2 = 0.11, P = .001). No quadriceps RTD variable was significantly associated with WOMAC function score (change in R2 range, <0.01‐0.017). • CONCLUSION: Involved‐limb quadriceps RTD was weakly associated with physical performance outcomes, but not self‐reported disability, in individuals with tibiofemoral osteoarthritis. Bilateral average quadriceps RTD was moderately associated with walking speed. • LEVEL OF EVIDENCE: Prognosis, level 2b. • KEY WORDS: chair stand, self‐reported function, stair climb, strength, walking speed

The Hypothalamic–Pituitary–Ovarian Axis and Oral Contraceptives: Regulation and Function

This chapter provides an overview of the hypothalamic–pituitary–ovarian (HPO) axis, otherwise known as the female reproductive axis. The HPO axis is the major regulator of the female reproductive hormones: estrogen and progesterone. Gonadotropin-releasing hormone is released from the hypothalamus at the onset of puberty in young women, and induces the release of luteinizing hormone (LH) and follicular stimulating hormone (FSH) from the anterior pituitary. These two hormones bind to ovarian receptors and signal the release of estrogen and progesterone. Estrogen and progesterone are released in fluctuating concentrations throughout the menstrual cycle, resulting in the follicular (low estrogen) phase and the luteal (high estrogen) phase. These phases are separated by ovulation and end with either fertilization or menstruation in a eumenorrheic woman.

Quadriceps rate of torque development and disability in individuals with anterior cruciate ligament reconstruction

Background The purpose of this study was to determine associations between self‐reported function (International Knee Documentation Committee Index), isometric quadriceps strength and rate of torque development in individuals with a unilateral anterior cruciate ligament reconstruction. Methods Forty‐one individuals [31% male, BMI mean 25 (SD 4) kg/m2, months post anterior cruciate ligament reconstruction mean 49 (SD 40)] completed the self‐reported function and isometric quadriceps function testing. Rate of torque development was assessed at 0–100 ms (early), 100–200 ms (late) ms, and peak following the onset of contraction. Associations were examined between rate of torque development, strength, and self‐reported function. Linear regression was used to determine the unique amount of variance explained by the combination of rate of torque development and strength. Findings Higher rate of torque development 100–200 ms is weakly associated with higher self‐reported function in individuals with a unilateral anterior cruciate ligament reconstruction (r = 0.274, p = 0.091); however, rate of torque development 100–200 ms does not predict a significant amount of variance in self‐reported function after accounting for strength (&Dgr;R2 = 0.003, P = 0.721). Interpretation Quadriceps strength has a greater influence on self‐reported function compared to rate of torque development in individuals with an anterior cruciate ligament reconstruction with time from surgery. HighlightsQuadriceps strength and function post anterior cruciate ligament surgery associateQuadriceps rate of torque development associates with self‐reported function.Rate of torque does not predict disability after accounting for strength.