Consistently High Urine Specific Gravity in Adolescent American Football Players and the Impact of an Acute Drinking Strategy

AbstractSickle cell trait (SCT) is a risk factor of collapse and sudden death in athletes. We conducted a longitudinal study to determine the hematological responses and hydration status in NCAA Division I American football players with SCT. The study took place over 2 years with 6 SCT and 6 position-matched controls (CON) in year 1; and 4 SCT and 4 CON in year 2. In year 2, three of the four SCT players were recruited and re-enrolled with new position-matched controls (total sample data = 10 SCT and 10 CON). Blood samples were taken at three visits: pre-camp, post-camp, and post-season to examine hemoglobin variants, complete blood counts, and chemistry panel 26. Hydration status was assessed by measuring body weight change, urine specific gravity, and urine and sweat electrolyte concentrations during the pre-season training camp. All SCT players were confirmed to have SCT (HbS = 37.9 ± 2.4%) and had greater red cell distribution width (RDW) compared to CON across all visits. Serum uric acid was higher in SCT (7.3 ± 1.0 mg/dL) compared to CON (6.1 ± 0.6 mg/dL; p = 0.001). Furthermore, serum creatine kinase levels were greater in SCT (1617.0 ± 1034.8 IU/L) at pre-camp compared to CON (1037.4 ± 602.8 IU/L; p = 0.03). SCT players exhibited lower pre- and post-practice urine electrolytes and urine specific gravity (SCT pre: 1.019 ± 0.005 vs. CON pre: 1.026 ± 0.008 p < 0.001; SCT post: 1.020 ± 0.005 vs. CON post: 1.030 ± 0.008 p < 0.01), whereas sweat sodium concentrations were higher in SCT players (55.4 ± 13.6 mmol/L) compared to CON (45.5 ± 10.6 mmol/L; p < 0.001). Given the evidence, greater uric acid and CPK levels in SCT players compared to CON may be an early indicator of altered kidney function and muscle damage, which could be added into NCAA guidelines for surveillance among SCT players. Consistent education and reinforcement of the importance of adequate fluid balance during exercise are critical for both SCT and CON players.

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Effects of sex and menstrual cycle on volume-regulatory responses to 24-h fluid restriction

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00173.2020 ◽

2020 ◽

Vol 319 (5) ◽

pp. R560-R565

Author(s):

Gabrielle E. W. Giersch ◽

Abigail T. Colburn ◽

Margaret C. Morrissey ◽

Cody R. Butler ◽

Michaela L. Pruchnicki ◽

...

Keyword(s):

Menstrual Cycle ◽

Specific Gravity ◽

Body Mass ◽

Urine Osmolality ◽

Reproductive Hormones ◽

Urine Specific Gravity ◽

Fluid Restriction ◽

Urine Color ◽

Fluid Regulation ◽

The Impact

Reproductive hormones have significant nonreproductive physiological effects, including altering fluid regulation. Our purpose was to explore the impact of sex and menstrual cycle (MC) phase on volume-regulatory responses to 24-h fluid restriction (24-h FR). Participants (men: n = 12, 20 ± 2 yr; women: n = 10, 20 ± 1 yr) were assigned two randomized and counterbalanced fluid prescriptions [Euhy: euhydrated, urine specific gravity (USG) < 1.020; Dehy: 24-h FR, USG > 1.020]. Men completed both (MEuhy, MDehy), while women completed both in the late-follicular ( days 10–13; FDehy, FEuhy) and midluteal ( days 18–22; LDehy, LEuhy) phases. We measured body mass, plasma and urine osmolality (Posm, Uosm), urine specific gravity (USG), urine color (Ucol), and serum copeptin; 24-h FR yielded mild dehydration without influence of sex or MC ( P > 0.05). Copeptin increased in men following Dehy (pre: 8.2 ± 5.2, post: 15.8 ± 12.6, P = 0.04) but not in women (FDehy pre: 4.3 ± 1.6, post: 10.5 ± 6.9, P = 0.06; LDehy pre: 5.6 ± 3.5, post: 10.4 ± 6.2, P = 0.16). In FDehy, Posm increased following FR (pre: 288 ± 2, post: 292 ± 1, P = 0.03) but not in men (pre: 292 ± 3, post: 293 ± 2, P = 0.46). No MC differences were observed between body mass loss, Posm, Uosm, USG, and copeptin ( P > 0.05). These results suggest that volume-regulatory responses to 24-h FR were present in men but not in women, without apparent effects of the menstrual cycle.

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Blood-Flow Restricted Warm-Up Alters Muscle Hemodynamics and Oxygenation during Repeated Sprints in American Football Players

Sports ◽

10.3390/sports7050121 ◽

2019 ◽

Vol 7 (5) ◽

pp. 121 ◽

Cited By ~ 5

Author(s):

Jean-François Fortin ◽

François Billaut

Keyword(s):

Blood Flow ◽

Near Infrared ◽

Hemoglobin Concentration ◽

American Football ◽

Football Players ◽

Warm Up ◽

Muscle Oxygen ◽

Metabolic Functions ◽

Parallel Group Design ◽

The Impact

Team-sport athletes and coaches use varied strategies to enhance repeated-sprint ability (RSA). Aside from physical training, a well-conducted warm-up enhances RSA via increased oxidative metabolism. Strategies that impede blood flow could potentiate the effects of a warm-up due to their effects on the endothelial and metabolic functions. This study investigated whether performing a warm-up combined with blood-flow restriction (WFR) induces ergogenic changes in blood volume, muscle oxygenation, and RSA. In a pair-matched, single-blind, pre-post parallel group design, 15 American football players completed an RSA test (12 × 20 m, 20 s rest), preceded by WFR or a regular warm-up (SHAM). Pressure was applied on the athletes’ upper thighs for ≈15 min using elastic bands. Both legs were wrapped at a perceived pressure of 7 and 3 out of 10 in WFR and SHAM, respectively. Changes in gastrocnemius muscle oxygen saturation (SmO2) and total hemoglobin concentration ([THb]) were monitored with near-infrared spectroscopy. Cohen’s effect sizes (ES) were used to estimate the impact of WFR. WFR did not clearly alter best sprint time (ES −0.25), average speed (ES 0.25), total time (ES −0.12), and percent decrement score (ES 0.39). While WFR did not meaningfully alter average SmO2 and [THb], the intervention clearly increased the maximum [THb] and the minimum and maximum SmO2 during some of the 12 sprint/recovery periods (ES 0.34–1.43). Results indicate that WFR positively alters skeletal muscle hemodynamics during an RSA test. These physiological changes did not improve short-term RSA, but could be beneficial to players during longer activities such as games.

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Similar head impact acceleration measured using instrumented ear patches in a junior rugby union team during matches in comparison with other sports

Journal of Neurosurgery Pediatrics ◽

10.3171/2015.12.peds15605 ◽

2016 ◽

Vol 18 (1) ◽

pp. 65-72 ◽

Cited By ~ 15

Author(s):

Doug A. King ◽

Patria A. Hume ◽

Conor Gissane ◽

Trevor N. Clark

Keyword(s):

Injury Risk ◽

Linear Acceleration ◽

Rugby Union ◽

Head Impact ◽

American Football ◽

Football Players ◽

Head Impacts ◽

Impact Acceleration ◽

The Impact ◽

Rugby Players

OBJECTIVE Direct impact with the head and the inertial loading of the head have been postulated as major mechanisms of head-related injuries, such as concussion. METHODS This descriptive observational study was conducted to quantify the head impact acceleration characteristics in under-9-year-old junior rugby union players in New Zealand. The impact magnitude, frequency, and location were collected with a wireless head impact sensor that was worn by 14 junior rugby players who participated in 4 matches. RESULTS A total of 721 impacts > 10g were recorded. The median (interquartile range [IQR]) number of impacts per player was 46 (IQR 37–58), resulting in 10 (IQR 4–18) impacts to the head per player per match. The median impact magnitudes recorded were 15g (IQR 12g–21g) for linear acceleration and 2296 rad/sec2 (IQR 1352–4152 rad/sec2) for rotational acceleration. CONCLUSIONS There were 121 impacts (16.8%) above the rotational injury risk limit and 1 (0.1%) impact above the linear injury risk limit. The acceleration magnitude and number of head impacts in junior rugby union players were higher than those previously reported in similar age-group sports participants. The median linear acceleration for the under-9-year-old rugby players were similar to 7- to 8-year-old American football players, but lower than 9- to 12-year-old youth American football players. The median rotational accelerations measured were higher than the median and 95th percentiles in youth, high school, and collegiate American football players.

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Influence of preanalytic and analytic variables in canine and feline urine specific gravity measurement by refractometer

Journal of Veterinary Diagnostic Investigation ◽

10.1177/1040638719896785 ◽

2019 ◽

Vol 32 (1) ◽

pp. 36-43

Author(s):

Martina Mösch ◽

Sven Reese ◽

Karin Weber ◽

Katrin Hartmann ◽

Roswitha Dorsch

Keyword(s):

Specific Gravity ◽

Storage Time ◽

Urine Specific Gravity ◽

Gravity Measurement ◽

Observer Variability ◽

Important Indicator ◽

Single Scale ◽

The Difference ◽

Whole Urine ◽

The Impact

Urine specific gravity (USG), which is usually measured by refractometry, is an important indicator of renal concentrating ability. Few studies have evaluated refractometers with separate scales for canine and feline urine. Variables such as protein content or storage time may influence the USG. We compared the effects of measuring USG with a refractometer with single or separate scales for canine and feline urine, investigated inter- and intra-observer variability, and measured agreement between whole urine and supernatant. We evaluated the correlation between USG and osmolality, the influence of urinary protein on USG and osmolality, and the impact of storage time up to 6 mo. We examined 252 canine and 126 feline samples. Bland–Altman analysis revealed higher USG values of the single-scale refractometer than the dual-scale refractometer, with a mean difference (bias) of < 0.001 for canine and 0.003 for feline specimens. Inter- and intra-observer variability were acceptable. Good agreement was shown between USG of whole urine and supernatant. Correlations between USG and osmolality were excellent (0.98–0.99, p < 0.001). Proteinuria up to 1 g/L had no major impact on USG or osmolality. Storage time had no significant effect on USG. The difference between the refractometers is clinically irrelevant, and the use of a refractometer with separate feline and canine scales is unnecessary. Whole urine and supernatant stored up to 6 mo can both be used for USG measurement. The influence of proteinuria <1 g/L on USG and osmolality is negligible.

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Hydration Status in College Football Players during Consecutive Days of Twice-a-Day Preseason Practices

The American Journal of Sports Medicine ◽

10.1177/0363546504270999 ◽

2005 ◽

Vol 33 (6) ◽

pp. 843-851 ◽

Cited By ~ 52

Author(s):

Sandra Fowkes Godek ◽

Joseph J. Godek ◽

Arthur R. Bartolozzi

Keyword(s):

Body Weight ◽

Specific Gravity ◽

Core Temperature ◽

Plasma Volume ◽

Sweat Rate ◽

Urine Samples ◽

Urine Specific Gravity ◽

Football Players ◽

Urine Sodium ◽

Before And After

Background Football players lose 3.5 to 5 kg of body weight during preseason practices because of heavy sweating. This fluid may be difficult to replace when practices occur 2 times per day on consecutive days. Hypothesis Football players are hypohydrated during twice-a-day preseason training in a hot, humid environment. Study Design Descriptive laboratory study Methods In 10 college football players, body weight was measured, and blood and urine samples were obtained before and after practices on days 2 through 8 of preseason training. Baseline samples were obtained when subjects were euhydrated. Blood samples were used to calculate plasma volume changes. Urine samples were analyzed for specific gravity, sodium, and potassium. Sweat rate was calculated. Core temperature was monitored during half- and full-padded practices. Results Mean wet bulb temperatures were 23.3°C during morning practices and 23.7°C during afternoon practices. Plasma volume was below baseline on day 2 and expanded by day 6. Urine specific gravity was higher than baseline for 12 of 20 measurements over the 8 days. It was 1.0175 ± 0.006 at baseline but subsequently ranged from 1.0214 ± 0.007 to 1.0321 ± 0.004. Mean daily urine sodium dropped from baseline to day 2 (194 ± 43 vs 43 ± 38 mmol × L-1), remaining lower on days 3, 4, and 6 (40 ± 39, 39 ± 39, and 68 ± 40 mmol × L-1, respectively). Urine potassium was lower on days 6 and 8 compared with baseline and day 3. Body weight was below baseline before and after both daily practices. Core temperature was higher in full pads; sweat rate and body weight loss were not different between half and full pads. Conclusion Body weight, plasma volume, urine specific gravity, and urine sodium indicate that football players become dehydrated by day 2 of preseason training. Urine sodium increased to near baseline by day 8; urine specific gravity was elevated. Clinical Relevance Football players struggle to maintain euhydration during preseason twice-a-day sessions.

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