表現增強物質

表現增強物質(Performance-enhancing substances)，也稱為表現增強藥物（performance-enhancing drugs,縮寫為PED），^[1]是用於改善人類任何形式的活動表現的物質。一個著名的例子是在體育運動中使用的藥物，運動員和健美運動員可能使用被體育界禁用的藥物。運動員在服食後因體能的增強，能顯著提升表現，但由於副作用巨大，因此是被禁止使用的。然而，由於現代生物醫學科技一日千里，藥物推陳出新，要完全杜絕難度極高，因此國際組織會將運動員的尿液樣本一直保存，並隨時翻驗。有時，學生會使用認知增強藥物（俗稱聰明藥）^[2]來提高學習成績。軍事人員也會使用增強表現的物質來增強戰鬥力。^[3]

表現增強藥物的使用涵蓋合法使用和藥物濫用的類別。

定義

物質作為提高性能的物質的分類並不完全明確和客觀。與其他類型的分類一樣，某些原型性能增強劑也被普遍分類（例如合成代謝類固醇），而其他物質（例如維生素和蛋白質補充劑）儘管對性能有影響，但實際上從未被分類為性能增強劑。與分類一樣，存在臨界情況。例如，咖啡因被某些人（而非所有人）視為性能增強劑。^[4]

類型

• 合成代謝藥物可以增強肌肉，例如類固醇^[5]、賀爾蒙（最著名的是生長激素）及其某些前藥^[6]、選擇性雄激素受體調節劑^[7]和β-2激動劑。^[8][9]

• 興奮劑可提高注意力和機敏性。低（治療）劑量的多巴胺類興奮劑（例如再攝取抑制劑和單胺釋放劑）還分別通過改善肌肉強度和耐力同時減少反應時間和疲勞來促進認知和運動表現，分別作為聰明藥和增效劑；^[10][11][12]一些可以提高運動成績的興奮劑包括咖啡因^[13]、麻黃鹼、派醋甲酯和苯丙胺。^{[10][11][12][14][15]}

• 運動表現增強藥物包括許多對身體成績有各種影響的藥物。苯丙胺和哌醋甲酯等藥物可在恆定的感知勞累水平下增加功率輸出並延遲疲勞發作^[14][15][16]，除其他運動表現增強效果外^[10][11][12]，安非他酮還可以在恆定的感知勞累水平上增加功率輸出，但僅限於短期使用^[16]。肌酸是運動員常用的營養補充品，可增加高強度運動能力。^[17]

• 人類生物分子 - 肌酸和β-羥基-β-甲基丁酸是人類中天然存在的化合物，在補充時對身體組成有影響。^[18]

• 聰明藥或“認知增強劑”通過改善記憶力而有益於整體認知（例如，增加工作內存容量或進行更新）或認知控制的其他方面（例如抑制控制、注意力控制、注意長度等）。^[2][19]

• 止痛藥能使表現超出通常的疼痛閾值。一些止痛藥會升高血壓，增加對肌肉細胞的氧氣供應。運動員使用的止痛藥包括非處方藥如非類固醇抗發炎藥（例如布洛芬）到功能強大的處方麻醉藥。

• 鎮靜劑和抗焦慮藥有時用於諸如射箭之類的運動中，需要穩定的手和準確的瞄準，還需要克服過度的緊張或不適感。地西泮和普萘洛爾是常見的例子；偶爾也使用乙醇和大麻。

• 血液增強劑使血液的攜氧能力超出個人的自然能力。它們用於耐力運動，例如長跑、騎自行車和越野滑雪。重組人類紅血球生成素（rhEPO）是該類別中最廣為人知的藥物之一。^[18]

參考資料

1. Effects of Performance-Enhancing Drugs | USADA. [2020-10-30]. （原始内容于2015-09-22）. 
2. Frati P, Kyriakou C, Del Rio A, Marinelli E, Vergallo GM, Zaami S, Busardò FP. Smart drugs and synthetic androgens for cognitive and physical enhancement: revolving doors of cosmetic neurology. Curr Neuropharmacol. January 2015, 13 (1): 5–11. PMC 4462043  . PMID 26074739. doi:10.2174/1570159X13666141210221750. Cognitive enhancement can be defined as the use of drugs and/or other means with the aim to improve the cognitive functions of healthy subjects in particular memory, attention, creativity and intelligence in the absence of any medical indication. ... The first aim of this paper was to review current trends in the misuse of smart drugs (also known as Nootropics) presently available on the market focusing in detail on methylphenidate, trying to evaluate the potential risk in healthy individuals, especially teenagers and young adults. 
3. Anon. Better Fighting Through Chemistry? The Role of FDA Regulation in Crafting the Warrior of the Future. （页面存档备份，存于互联网档案馆） Food and Drug Law: Final Paper. March 8, 2004.
4. Caffeine and Sports Performance. Vanderbilt.edu. [2012-03-04]. （原始内容于2012-02-29）. 
5. What are anabolic steroids?. National Institute on Drug Abuse. August 2006 [2016-04-11]. （原始内容于2018-02-20）. 
6. McKelvey Martin, Valerie. . [15 April 2013]. （原始内容存档于2013-04-15）. 
7. Mohler ML, Bohl CE, Jones A, Coss CC, Narayanan R, He Y, Hwang DJ, Dalton JT, Miller DD. Nonsteroidal selective androgen receptor modulators (SARMs): dissociating the anabolic and androgenic activities of the androgen receptor for therapeutic benefit. Journal of Medicinal Chemistry. June 2009, 52 (12): 3597–617. PMID 19432422. doi:10.1021/jm900280m. 
8. Drug Enforcement Administration. November 2013 Clenbuterol （页面存档备份，存于互联网档案馆）
9. Pluim BM, de Hon O, Staal JB, et al. β₂-Agonists and physical performance: a systematic review and meta-analysis of randomized controlled trials. Sports Med. January 2011, 41 (1): 39–57. PMID 21142283. doi:10.2165/11537540-000000000-00000. 
10. Liddle DG, Connor DJ. Nutritional supplements and ergogenic Aids. Prim. Care. June 2013, 40 (2): 487–505. PMID 23668655. doi:10.1016/j.pop.2013.02.009. Amphetamines and caffeine are stimulants that increase alertness, improve focus, decrease reaction time, and delay fatigue, allowing for an increased intensity and duration of training ...
    Physiologic and performance effects [of amphetamines]
     · Amphetamines increase dopamine/norepinephrine release and inhibit their reuptake, leading to central nervous system (CNS) stimulation
     · Amphetamines seem to enhance athletic performance in anaerobic conditions 39 40
     · Improved reaction time
     · Increased muscle strength and delayed muscle fatigue
     · Increased acceleration
     · Increased alertness and attention to task 
11. Parr JW. Attention-deficit hyperactivity disorder and the athlete: new advances and understanding. Clin. Sports Med. July 2011, 30 (3): 591–610. PMID 21658550. doi:10.1016/j.csm.2011.03.007. In 1980, Chandler and Blair⁴⁷ showed significant increases in knee extension strength, acceleration, anaerobic capacity, time to exhaustion during exercise, pre-exercise and maximum heart rates, and time to exhaustion during maximal oxygen consumption (VO2 max) testing after administration of 15 mg of dextroamphetamine versus placebo. Most of the information to answer this question has been obtained in the past decade through studies of fatigue rather than an attempt to systematically investigate the effect of ADHD drugs on exercise. ... In 2008, Roelands and colleagues⁵³ studied the effect of reboxetine, a pure NE reuptake inhibitor, similar to atomoxetine, in 9 healthy, well-trained cyclists. They too exercised in both temperate and warm environments. They showed decreased power output and exercise performance at both 18 and 30 degrees centigrade. Their conclusion was that DA reuptake inhibition was the cause of the increased exercise performance seen with drugs that affect both DA and NE (MPH, amphetamine, and bupropion). 
12. Parker KL, Lamichhane D, Caetano MS, Narayanan NS. Executive dysfunction in Parkinson's disease and timing deficits. Front. Integr. Neurosci. October 2013, 7: 75. PMC 3813949  . PMID 24198770. doi:10.3389/fnint.2013.00075. Manipulations of dopaminergic signaling profoundly influence interval timing, leading to the hypothesis that dopamine influences internal pacemaker, or “clock,” activity. For instance, amphetamine, which increases concentrations of dopamine at the synaptic cleft advances the start of responding during interval timing, whereas antagonists of D2 type dopamine receptors typically slow timing;... Depletion of dopamine in healthy volunteers impairs timing, while amphetamine releases synaptic dopamine and speeds up timing. 
13. Pesta DH, Angadi SS, Burtscher M, Roberts CK. The effects of caffeine, nicotine, ethanol, and tetrahydrocannabinol on exercise performance. Nutr Metab (Lond). 2013, 10 (1): 71. PMC 3878772  . PMID 24330705. doi:10.1186/1743-7075-10-71. Caffeine-induced increases in performance have been observed in aerobic as well as anaerobic sports (for reviews, see [26,30,31]). Trained athletes seem to benefit from a moderate dose of 5 mg/kg [32], however, even lower doses of caffeine (1.0–2.0 mg/kg) may improve performance [33]. Some groups found significantly improved time trial performance [34] or maximal cycling power [35], most likely related to a greater reliance on fat metabolism and decreased neuromuscular fatigue, respectively. Theophylline, a metabolite of caffeine, seems to be even more effective in doing so [36]. The effect of caffeine on fat oxidation, however, may only be significant during lower exercise intensities and may be blocked at higher intensities [37]. ... For both caffeine-naïve as well as caffeine-habituated subjects, moderate to high doses of caffeine are ergogenic during prolonged moderate intensity exercise [61]. ... In summary, caffeine, even at physiological doses (3–6 mg/kg), as well as coffee are proven ergogenic aids and as such – in most exercise situations, especially in endurance-type events – clearly work-enhancing [26]. It most likely has a peripheral effect targeting skeletal muscle metabolism as well as a central effect targeting the brain to enhance performance, especially during endurance events (see Table 1). Also for anaerobic tasks, the effect of caffeine on the CNS might be most relevant. ... Muendel et al. [93] found a 17% improvement in time to exhaustion after nicotine patch application compared to a placebo without affecting cardiovascular and respiratory parameters or substrate metabolism. In this sense, nicotine seems to exert similar effects as caffeine by delaying the development of central fatigue as impaired central drive is an important factor contributing to fatigue during exercise. ... The physiological effects of the above mentioned substances are well established. However, the ergogenic effect of some of the discussed drugs may be questioned and one has to consider the cohort tested for every specific substance. However, only caffeine has enough strength of evidence to be considered an ergogenic aid. 
14. Roelands B, de Koning J, Foster C, Hettinga F, Meeusen R. Neurophysiological determinants of theoretical concepts and mechanisms involved in pacing. Sports Med. May 2013, 43 (5): 301–311. PMID 23456493. doi:10.1007/s40279-013-0030-4. 
15. Rattray B, Argus C, Martin K, Northey J, Driller M. Is it time to turn our attention toward central mechanisms for post-exertional recovery strategies and performance?. Front. Physiol. March 2015, 6: 79. PMC 4362407  . PMID 25852568. doi:10.3389/fphys.2015.00079. Aside from accounting for the reduced performance of mentally fatigued participants, this model rationalizes the reduced RPE and hence improved cycling time trial performance of athletes using a glucose mouthwash (Chambers et al., 2009) and the greater power output during a RPE matched cycling time trial following amphetamine ingestion (Swart, 2009). ... Dopamine stimulating drugs are known to enhance aspects of exercise performance (Roelands et al., 2008) 
16. Roelands B, De Pauw K, Meeusen R. Neurophysiological effects of exercise in the heat. Scand. J. Med. Sci. Sports. June 2015,. 25 Suppl 1: 65–78. PMID 25943657. doi:10.1111/sms.12350. Physical fatigue has classically been attributed to peripheral factors within the muscle (Fitts, 1996), the depletion of muscle glycogen (Bergstrom & Hultman, 1967) or increased cardiovascular, metabolic, and thermoregulatory strain (Abbiss & Laursen, 2005; Meeusen et al., 2006b). In recent decennia however, it became clear that the central nervous system plays an important role in the onset of fatigue during prolonged exercise (Klass et al., 2008), certainly when ambient temperature is increased ... 5-HT, DA, and NA have all been implicated in the control of thermoregulation and are thought to mediate thermoregulatory responses, certainly since their neurons innervate the hypothalamus (Roelands & Meeusen, 2010). ... This indicates that subjects did not feel they were producing more power and consequently more heat. The authors concluded that the “safety switch” or the mechanisms existing in the body to prevent harmful effects are overridden by the drug administration (Roelands et al., 2008b). Taken together, these data indicate strong ergogenic effects of an increased DA concentration in the brain, without any change in the perception of effort. ... The combined effects of DA and NA on performance in the heat were studied by our research group on a number of occasions. ... the administration of bupropion (DA/NA reuptake inhibitor) significantly improved performance. Coinciding with this ergogenic effect, the authors observed core temperatures that were much higher compared with the placebo situation. Interestingly, this occurred without any change in the subjective feelings of thermal sensation or perceived exertion. Similar to the methylphenidate study (Roelands et al., 2008b), bupropion may dampen or override inhibitory signals arising from the central nervous system to cease exercise because of hyperthermia, and enable an individual to continue maintaining a high power output 
17. Buford TW, Kreider RB, Stout JR, Greenwood M, Campbell B, Spano M, Ziegenfuss T, Lopez H, Landis J, Antonio J. International Society of Sports Nutrition position stand: creatine supplementation and exercise. J Int Soc Sports Nutr. 2007, 4: 6. PMC 2048496  . PMID 17908288. doi:10.1186/1550-2783-4-6. 
18. Momaya A, Fawal M, Estes R. Performance-enhancing substances in sports: a review of the literature. Sports Med. April 2015, 45 (4): 517–531. PMID 25663250. doi:10.1007/s40279-015-0308-9. 
19. Ilieva IP, Hook CJ, Farah MJ. Prescription Stimulants' Effects on Healthy Inhibitory Control, Working Memory, and Episodic Memory: A Meta-analysis. J. Cogn. Neurosci. January 2015, 27 (6): 1069–89 [2020-10-30]. PMID 25591060. doi:10.1162/jocn_a_00776. （原始内容于2018-09-19）. The present meta-analysis was conducted to estimate the magnitude of the effects of methylphenidate and amphetamine on cognitive functions central to academic and occupational functioning, including inhibitory control, working memory, short-term episodic memory, and delayed episodic memory. In addition, we examined the evidence for publication bias. Forty-eight studies (total of 1,409 participants) were included in the analyses. We found evidence for small but significant stimulant enhancement effects on inhibitory control and short-term episodic memory. Small effects on working memory reached significance, based on one of our two analytical approaches. Effects on delayed episodic memory were medium in size. However, because the effects on long-term and working memory were qualified by evidence for publication bias, we conclude that the effect of amphetamine and methylphenidate on the examined facets of healthy cognition is probably modest overall. In some situations, a small advantage may be valuable, although it is also possible that healthy users resort to stimulants to enhance their energy and motivation more than their cognition. ... Earlier research has failed to distinguish whether stimulants’ effects are small or whether they are nonexistent (Ilieva et al., 2013; Smith & Farah, 2011). The present findings supported generally small effects of amphetamine and methylphenidate on executive function and memory. Specifically, in a set of experiments limited to high-quality designs, we found significant enhancement of several cognitive abilities. ...
    
    The results of this meta-analysis cannot address the important issues of individual differences in stimulant effects or the role of motivational enhancement in helping perform academic or occupational tasks. However, they do confirm the reality of cognitive enhancing effects for normal healthy adults in general, while also indicating that these effects are modest in size. 

外部連結

•   维基共享资源上的相關多媒體資源：表現增強物質