Physiological and health characteristics of ex-jockeys

Weight-Making Practices Among Jockeys: An Update and Review of the Emergent Scientific Literature

Numerous publications have described the behaviors employed by professional jockeys on a daily basis to achieve and maintain a minimum racing weight. This narrative review provides an update of recent publications that report on the impact of such practices. Although rapid weight-loss techniques such as calorie restriction and dehydration are commonly thought to be deleterious to jockeys, little evidence exists of enduring health consequences. There is evidence to suggest that jockey training behaviors and dietary choices are not aligned with optimum preparation for the physiological demands of the sport. Further research is necessary to better measure the health impact of jockey weight-making behaviors; such data might guide reforms of athlete behavior and regulatory practices within the global sport of horse racing.

Proposed injury thresholds for concussion in equestrian sports

OBJECTIVES

Equestrian helmets are designed to pass certification standards based on linear drop tests onto rigid steel surfaces. However, concussions in equestrian sports occur most commonly when a rider is thrown off a horse and obliquely impacts a compliant surface such as turf or sand. This paper seeks to elucidate the mechanics of such impacts and thereby propose corresponding thresholds for the occurrence of concussion that can improve equestrian helmet standards and designs.

DESIGN

The present study examined the biomechanics of real-world equestrian accidents and developed thresholds for the occurrence of concussive injury.

METHODS

Twenty-five concussive and 25 non-concussive falls in equestrian sports were reconstructed using a combination of video analysis, computational and physical reconstruction methods. These represented male and female accidents from horse racing and the cross-country phase of eventing.

RESULTS

The resulting thresholds for concussion [59g, 2700rad/s², 28rad/s, 0.24 (MPS), 6.6kPa and 0.27 (CSMD₁₀) for 50% risk] were consistent with those reported in the literature and represent a unique combination of head kinematic thresholds compared to other sports. Current equestrian helmet standards commonly use a threshold of 250g and a linear drop to a steel anvil resulting in less than 15ms impacts. This investigation found that concussive equestrian accidents occurred from oblique impacts to turf or sand with lower magnitude and longer duration impacts (<130g and >20ms). This suggests that current equestrian helmet standards may not adequately represent real-world concussive impact conditions and, consequently, there is an urgent need to assess the protective capacity of equestrian helmets under real-world conditions.

Are predictive equations a valid method of assessing the resting metabolic rate of overweight or obese former athletes?

Athletes retiring from their sports career, an understudied population, are susceptible to become overweight/obese because of decreased energy expenditure not followed by a reduction in energy intake. Therefore, their energy requirements, through resting metabolic rate (RMR), should be accurately addressed for weight management purposes. This study aimed to determine the validity of predictive equations (PEq) for RMR estimation using indirect calorimetry as the reference method in a sample of overweight/obese former athletes. The study uses cross-sectional data collected during baseline measurements of a lifestyle intervention (NCT03031951). The RMR of 56 overweight/obese (31.5 (4.0 kg/m²)) individuals (78.6% male, 37.5% obese, 95.8 (14.8 kg), 174.2 (8.7 cm)) was measured by indirect calorimetry and predicted using seven PEq: Harris-Benedict, Cunningham, Schofield, FAO/WHO/UNU, Owen, Mifflin-St. Jeor, and Katch-McArdle. Dual-energy X-ray absorptiometry was used to assess body composition. The PEq overestimated the RMR measured by the indirect calorimetry, 70-300 kcal/day (4.3-14.9%). The linear regression between the reference and each of the PEq did not differ from the identity line with estimated values explaining around 50% of the variability of the measured values. The agreement between the methods was weak for all the PEq showing wide limits of agreement. The Harris-Benedict equation was the only one in which the difference between the methods was not related to the magnitude of the measured RMR. Given the weak performance of the various RMR models in overweight/obese former athletes, an effective weight management intervention based on estimated resting energy requirements may be compromised.

Limb muscle quality and quantity in elderly adults with dynapenia but not sarcopenia: An ultrasound imaging study

BACKGROUND

Dynapenia is prevalent in people with reduced skeletal muscle mass, i.e. sarcopenia, but a certain population develops muscle strength loss despite having normal skeletal muscle volume. To date, studies investigating muscle quality and quantity in groups with dynapenia but not sarcopenia are limited.

METHODS

Echogenicity and thickness of the biceps brachii, triceps brachii, rectus femoris, and medial gastrocnemius muscles were measured using high-resolution ultrasonography in 140 community-dwelling elderly adults. Participants with decreased handgrip strength but normal muscular volume were diagnosed as having dynapenia without sarcopenia. A multivariate regression model was used to analyze the association between dynapenia and ultrasound indicators of the sampled muscle expressed as odds ratio (OR) and 95% confidence interval (CI).

RESULTS

A total of 140 participants were recruited for the study, 12.6% (n = 18) of whom had dynapenia. The dynapenia group had a higher mean age, higher proportion of women, slower fast gait speed, reduced handgrip strength, and decreased thicknesses of the biceps brachii, rectus femoris, and medial gastrocnemius muscles. On multivariate logistic regression analysis, dynapenia was associated with older age (OR, 1.18; 95% CI, 1.05 to 1.33), higher body mass index (OR, 1.28; 95% CI, 1.05 to 1.64), and decreased thicknesses of the rectus femoris (OR, 0.01; 95% CI, <0.01 to 0.24) and medial gastrocnemius muscles (OR, 0.03; 95% CI, <0.01 to 0.61).

CONCLUSION

Dynapenia without sarcopenia is associated with decreased thicknesses of the rectus femoris and medial gastrocnemius muscles, an association that remains significant after adjustment for demographics, body composition, and physical performance. Ultrasound measurements of lower-limb muscle thickness can be considered an auxiliary criterion for evaluating dynapenia.

Gender and Weight among Thoroughbred Jockeys: Underrepresented Women and Underweight Men

Discrimination can damage health by limiting an occupation to persons who are physically unsuited to it. In thoroughbred racing, male jockeys damage their health to reach racing weights, while women who could reach those weights more easily are excluded. The authors estimate the number of U.S. men and women who are light enough to work as jockeys and contrast them with the number of male and female jockeys. The authors contrast the distribution of body mass index in the general population and among top jockeys. Male jockeys outnumber female jockeys by 7 to 1, and by 50 to 1 in top races, and these numbers have not declined since the 1990s. Yet among adults who are light enough to work as jockeys, women outnumber men by at least 7 to 1, and women are half as likely to be underweight. Jockeys' health and performance might improve if barriers to women were lowered.