Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
J Anim Sci. 2021 Oct 1;99(10). doi: 10.1093/jas/skab264.
Consumption of β-hydroxy β-methylbutyrate (HMB) alters muscle composition and metabolism leading to strength and agility improvements in human athletes. To determine if HMB affects athletic performance and muscle function in horses, Thoroughbred geldings were fed a control (CON; n = 5) or HMB (n = 6) supplement for 6 wk prior to completing a standardized exercise test (SET). Gluteus medius (GM) muscle biopsies were obtained before the SET for fiber typing. Heart rate, biceps femoris (BF) and semitendinosus (ST) surface electromyograms (EMG), and fore and hind limbs metacarpophalangeal joint angles were captured at the gallop of the SET. Results demonstrate that HMB supplementation increased (P < 0.05) the percentage of type IIA and IIA/X muscle fibers in the GM with a corresponding decrease (P < 0.05) in type IIX fibers. The percentage of type I fibers was unaffected by diet. Supplementation with HMB did not result in any measurable effects on performance or biomechanical properties by comparison to CON. Supplementation with HMB resulted in an increase (P < 0.05) in ST median frequency at speeds of 10 m/s and greater. Increasing treadmill speed resulted in an increase (P < 0.05) in stride length and the maximal proximal forelimb fetlock angle, and a decrease (P < 0.05) in stance phase time of the gait cycle. Integrated EMG (iEMG) increased (P < 0.05) with increasing treadmill speeds for both the BF and ST with the BF exhibiting greater (P < 0.05) iEMG values than the ST. In summary, HMB increased the percentage of type IIA GM fibers, which did not translate into improved performance.
β-羟基-β-甲基丁酸（HMB）的消耗会改变肌肉组成和代谢，从而提高人类运动员的力量和敏捷度。为了确定 HMB 是否会影响马的运动表现和肌肉功能，我们给 5 匹公马喂食对照（CON）饲料，6 匹公马喂食 HMB 补充剂，持续 6 周，然后让它们完成标准化运动测试（SET）。在 SET 之前，我们采集了臀中肌（GM）肌肉活检样本，用于纤维分型。在 SET 的疾驰过程中，我们记录了心率、股二头肌（BF）和半腱肌（ST）的表面肌电图（EMG），以及前肢和后肢掌指关节的角度。结果表明，HMB 补充剂增加了 GM 中 IIA 型和 IIA/X 型肌肉纤维的比例（P < 0.05），同时 IIX 型纤维的比例相应下降（P < 0.05）。饮食对 I 型纤维的比例没有影响。与 CON 相比，HMB 补充剂对性能或生物力学特性没有产生任何可测量的影响。与 CON 相比，HMB 补充剂使 ST 中值频率在 10m/s 及以上的速度下增加（P < 0.05）。增加跑步机速度会导致步幅长度增加（P < 0.05），最大前肢球节角度增加（P < 0.05），步态周期的站立阶段时间减少（P < 0.05）。BF 和 ST 的 iEMG 随着跑步机速度的增加而增加（P < 0.05），BF 的 iEMG 值大于 ST（P < 0.05）。总之，HMB 增加了 GM 中 IIA 型纤维的比例，但这并没有转化为性能的提高。
