Kathleen N. Beasley

Changes in serum collagen markers, IGF‐I, and Knee joint laxity across the menstrual cycle

Variations in serum markers of collagen production (CICP) and degradation (ICTP), insulin‐like growth factor I (IGF‐I) and anterior knee laxity (AKL) were measured in 20 women [10 with spontaneous cycles (eumenorrheic), 10 using oral contraceptives] over 5 consecutive days at menses (M1–M5, 1st pill week), the initial estrogen rise near ovulation (O1–O5, 2nd pill week), the initial progesterone rise of the early luteal phase (EL1–EL5, 3rd pill week) and post‐progesterone peak of the late luteal phase (LL1–LL5, 4th pill week). ICTP was higher in oral contraceptive women (5.3 ± 1.7 vs. 3.7 ± 1.3 µg/L; p = 0.030), primarily during days near ovulation and the early luteal phase when concentrations decreased in eumenorrheic women (p = 0.04). IGF‐I concentrations increased during menses then decreased and remained lower during the early and late luteal phase in oral contraceptive women, resulting in lower concentrations compared to eumenorrheic women at EL2 and LL1 (p = 0.03). CICP decreased in early and late luteal days (p <0.01), and there was a trend toward lower concentrations in eumenorrheic versus oral contraceptive women (85.7 ± 35.7 ng/ml vs. 123.2 ± 49.8 ng/ml; p = 0.07). Lower CICP and greater IGF‐I concentrations predicted greater AKL across the 20 cycle days in both groups (R2 = 0.310 and 0.400). Sex hormone concentration changes across the menstrual cycle are of sufficient magnitude to influence collagen metabolism, and may indirectly influence knee structure and function.

IGF-I measurement across blood, interstitial fluid, and muscle biocompartments following explosive, high-power exercise

Insulin-like growth factor-I (IGF-I) resides across different biocompartments [blood, interstitial fluid (ISF), and muscle]. Whether circulating IGF-I responses to exercise reflect local events remains uncertain. We measured the IGF-I response to plyometric exercise across blood, ISF, and muscle biopsy from the vastus lateralis. Twenty volunteers (8 men, 12 women, 22 ± 1 yr) performed 10 sets of 10 plyometric jump repetitions at a 40% 1-repetition maximum. Blood, ISF, and muscle samples were taken pre- and postexercise. Circulating IGF-I increased postexercise: total IGF-I (preexercise = 546 ± 42, midexercise = 585 ± 43, postexercise = 597 ± 45, +30 = 557 ± 42, +60 = 536 ± 40, +120 = 567 ± 42 ng/ml; midexercise, postexercise, and +120 greater than preexercise, P < 0.05); Free IGF-I (preexercise = 0.83 ± 0.09, midexercise = 0.78 ± 0.10, postexercise = 0.79 ± 0.11, +30 = 0.93 ± 0.10, +60 = 0.88 ± 0.10, + 120 = 0.91 ± 0.11 ng/ml; +30 greater than all other preceding time points, P < 0.05). No exercise-induced changes were observed for ISF IGF-I (preexercise = 2.35 ± 0.29, postexercise = 2.46 ± 0.35 ng/ml). No changes were observed for skeletal muscle IGF-I protein, although IGF-I mRNA content increased ∼40% postexercise. The increase in circulating total and free IGF-I was not correlated with increases in ISF IGF-I or muscle IGF-I protein content. Our data indicate that exercise-induced increases in circulating IGF-I are not reflective of local IGF-I signaling.

The influence of rehydration mode after exercise dehydration on cardiovascular function.

Abstract McDermott, BP, Casa, DJ, Lee, EC, Yamamoto, LM, Beasley, KN, Emmanuel, H, Pescatello, LS, Kraemer, WJ, Anderson, JM, Armstrong, LE, and Maresh, CM. The influence of rehydration mode after exercise dehydration on cardiovascular function. J Strength Cond Res 27(8): 2086–2095, 2013—Our purpose was to compare the common modes of rehydration (REHY) on cardiovascular and fluid regulation recovery after exercise dehydration (EXDE). Twelve nonheat-acclimatized trained subjects (age: 23 ± 4 years, weight: 81.3 ± 3.7 kg, height: 180 ± 6 cm, V[Combining Dot Above]O2max: 56.9 ± 4.4 ml·min−1·kg−1 , and body fat: 7.8 ± 3.0%) completed 20-hour fluid restriction and 2-hour EXDE to −4% body mass, and then were rehydrated to −2% body mass in a randomized, crossover design. The REHY methods included no fluid (NF), ad libitum, oral (OR), intravenous (IV), and a combination of IV and OR (IV + OR) of 1/2-normal saline (0.45% NaCl). The REHY occurred for 30 minutes, and the subjects were observed during rest for 30 minutes. Seated, standing, and mean arterial pressure (MAP) and blood pressure (BP) were measured every 15 minutes throughout REHY. Heart rate (HR), plasma arginine vasopressin concentration [AVP], and thirst perception were measured throughout REHY. The EXDE resulted in a body mass loss of 4.32 ± 0.22%. The REHY returned the subjects to −2.13 ± 0.47% body mass for controlled trials. Seated systolic BP was greater for IV + OR compared with that for OR (p = 0.015). Seated systolic BP and MAP during REHY showed that IV + OR was greater than OR, independent of time (p ⩽ 0.011). Upon standing, IV + OR demonstrated a greater BP than both NF (p = 0.012) and OR (p = 0.031) did. The HR was reduced by IV and IV + OR to a greater extent than NF at REHY30 and REHY60 (p < 0.05). The IV + OR [AVP] demonstrated a strong trend for decreasing over time (p = 0.054) and was significantly less than NF at REHY60 (p = 0.003). Practical application seeking to restore cardiovascular function after EXDE, the combined use of IV + OR rather than a single REHY method seems to be most expedient.

Thermoregulation and Stress Hormone Recovery After Exercise Dehydration: Comparison of Rehydration Methods

CONTEXT Athletic trainers recommend and use a multitude of rehydration (REHY) methods with their patients. The REHY modality that most effectively facilitates recovery is unknown. OBJECTIVE To compare 5 common REHY methods for thermoregulatory and stress hormone recovery after exercise dehydration (EXDE) in trained participants. DESIGN Randomized, cross-over, controlled study. PATIENTS OR OTHER PARTICIPANTS Twelve physically active, non-heat-acclimatized men (age = 23 ± 4 years, height = 180 ± 6 cm, mass = 81.3 ± 3.7 kg, VO2max = 56.9 ± 4.4 mL·min(-1)·kg(-1), body fat = 7.9% ± 3%) participated. INTERVENTION(S) Participants completed 20-hour fluid restriction and 2-hour EXDE; they then received no fluid (NF) or REHY (half-normal saline) via ad libitum (AL), oral (OR), intravenous (IV), or combination IV and OR (IV + OR) routes for 30 minutes; and then were observed for another 30 minutes. MAIN OUTCOME MEASURE(S) Body mass, rectal temperature, 4-site mean weighted skin temperature, plasma stress hormone concentrations, and environmental symptoms questionnaire (ESQ) score. RESULTS Participants were hypohydrated (body mass -4.23% ± 0.22%) post-EXDE. Rectal temperature for the NF group was significantly greater than for the IV group (P = .023) at 30 minutes after beginning REHY (REHY30) and greater than OR, IV, and IV + OR (P ≤ .009) but not AL (P = .068) at REHY60. Mean weighted skin temperature during AL was less than during IV + OR at REHY5 (P = .019). The AL participants demonstrated increased plasma cortisol concentrations compared with IV + OR, independent of time (P = .015). No differences existed between catecholamine concentrations across treatments (P > .05). The ESQ score was increased at REHY60 for NF, AL, OR, and IV (P < .05) but not for IV + OR (P = .217). The NF ESQ score was greater than that of IV + OR at REHY60 (P = .012). CONCLUSIONS Combination IV + OR REHY reduced body temperature to a greater degree than OR and AL REHY when compared with NF. Future studies addressing clinical implications are needed.

Appearance of D2O in sweat after oral and oral-intravenous rehydration in men.

Emmanuel, H, Casa, DJ, Beasley, KN, Lee, EC, McDermott, BP, Yamamoto, LM, Armstrong, LE, and Maresh, CM. Appearance of D2O in sweat after oral and oral-intravenous rehydration in men. J Strength Cond Res 25(8): 2092-2099, 2011—Intravenous (IV) rehydration is common in athletics, but its thermoregulatory benefits and ergogenicity have not been elucidated. Availability of orally ingested fluid is dependent on gastric emptying and intestinal absorption rate. Deuterium oxide (D2O) has been used to demonstrate that fluid ingested during exercise appears in sweat within 10 minutes. The purpose of this study was to determine the effect of concurrent IV rehydration on D2O appearance in sweat samples after per ora rehydration with D2O labeled fluid. We hypothesized that the combination method would not be superior to the oral method. Ten fit men (age 23 ± 4, &OV0312;O2max 59.49 ± 4.09 L·min−1) underwent 20 hours of fluid restriction resulting in 1.95 ± 0.25% body weight loss before beginning treadmill exercise and cycling. Exercise was performed in an environmental chamber (35.6 ± 0.2° C, 35.0 ± 1.8% relative humidity) for 2 hours at 55% &OV0312;O2max, and the participants exhibited a mean body weight deficit of 4.50 ± 0.04%. Thermoregulatory measures were recorded while subjects were rehydrated with oral (OR) or oral combined with intravenous (IVO) fluid traced with D2O. After 30 minutes of rehydration and 30 minutes of seated recovery, the subjects began treadmill exercise at 55-60% &OV0312;O2max. Forehead sweat samples were collected 0, 5, 10, 20, and 75 minutes from the start of rehydration. The samples were analyzed for D2O via isotope ratio mass spectrometry. D2O did not appear in the sweat within 20 minutes of rehydration; however, it did appear during the subsequent exercise bout. There was no significant difference between rehydration modes. Plasma volume increases and decreased volume of orally ingested fluid did not significantly alter transit time from ingestion to appearance in excreted sweat. The IVO method does not appear to be superior to the traditional OR method of rehydration.

The Effect of Oral Vs. Intravenous Rehydration on Circulating Myoglobin and Creatine Kinase

Beasley, KN, Lee, EC, McDermott, BP, Yamamoto, LM, Emmanuel, H, Casa, DJ, Armstrong, LE, Kraemer, WJ, and Maresh, CM. The effect of oral vs. intravenous rehydration on circulating myoglobin and creatine kinase. J Strength Cond Res 24(1): 60-67, 2010-Physical activity of significant intensity and duration may cause varying degrees of skeletal muscle damage, but it is unclear whether mode of rehydration will attenuate muscle tissue disruption caused by exercise in the heat. To examine the effects of the mode of rehydration on markers of muscle damage (myoglobin and creatine kinase [CK]), 11 healthy active men (age = 23 ± 4 years, body mass = 80.9 ± 3.9 kg, height = 180.5 ± 5.4 cm) completed 4 experimental trials consisting of an exercise dehydration protocol (to −4% of baseline body mass), followed by a rehydration period (oral, intravenous [IV], oral and IV combined, and ad libitum), and finishing with an intense exercise challenge that included treadmill running and sprinting and a box lifting protocol. During rehydration, subjects returned to −2% of baseline body mass unless completing the ad libitum trial during which they consumed fluids as thirst dictated. Myoglobin (Mb) and CK were measured during euhydrated rest. Post-exercise blood was drawn at 1 and 24 hours post exercise challenge for Mb and CK, respectively. Urine was collected during euhydrated rest and 1-hour post exercise challenge for measurement of Mb clearance. Mb concentrations increased significantly from pre (1.06 ± 0.20, 0.88 ± 0.07, 1.15 ± 0.25 and 0.92 ± 0.06 nmol·L−1) to post (1.52 ± 0.28, 1.44 ± 0.11, 1.71 ± 0.45 and 1.58 ± 0.39) for IV, oral, oral and IV combined, and ad libitum, respectively, but were not significantly different among trials. Serum CK concentrations remained within the normal physiological range for all trials. Thus, despite previous research that clearly indicates the benefit of ingesting fluids during exercise to attenuate muscle damage, there were no significant differences between the modes of rehydration on circulating Mb and CK.