Abstract
Caffeine supplementation during whole-/lower-body exercise is well-researched, yet evidence of its effect during upper-body exercise is equivocal. The current study explored the effects of caffeine on cycling/handcycling 10 km time trial (TT) performance in habitual caffeine users. Eleven recreationally trained males (mean (SD) age 24 (4) years, body mass 85.1 (14.6) kg, cycling/handcycling peak oxygen uptake (peak) 42.9 (7.3)/27.6 (5.1) mL∙kg∙min−1, 160 (168) mg/day caffeine consumption) completed two maximal incremental tests and two familiarization sessions. During four subsequent visits, participants cycled/handcycled for 30 min at 65% mode-specific peak (preload) followed by a 10 km TT following the ingestion of 4 mg∙kg−1 caffeine (CAF) or placebo (PLA). Caffeine significantly improved cycling (2.0 (2.0)%; 16:35 vs. 16:56 min; p = 0.033) but not handcycling (1.8 (3.0)%; 24:10 vs. 24:36 min; p = 0.153) TT performance compared to PLA. The improvement during cycling can be attributed to the increased power output during the first and last 2 km during CAF. Higher blood lactate concentration (Bla) was reported during CAF compared to PLA (p < 0.007) and was evident 5 min post-TT during cycling (11.2 ± 2.6 and 8.8 ± 3.2 mmol/L; p = 0.001) and handcycling (10.6 ± 2.5 and 9.2 ± 2.9 mmol/L; p = 0.006). Lower overall ratings of perceived exertion (RPE) were seen following CAF during the preload (p < 0.05) but not post-TT. Lower peripheral RPE were reported at 20 min during cycling and at 30 min during handcycling, and lower central RPE was seen at 30 min during cycling (p < 0.05). Caffeine improved cycling but not handcycling TT performance. The lack of improvement during handcycling may be due to the smaller active muscle mass, elevated (Bla) and/or participants’ training status.
Highlights
Low-moderate doses of caffeine (3–6 mg per kilogram of body weight) have been shown to positively influence cycling time-trial (TT) performance [1,2]
Higher blood lactate concentration (Bla) was reported during CAF compared to PLA (p < 0.007) and was evident 5 min post-TT during cycling (11.2 ̆ 2.6 and 8.8 ̆ 3.2 mmol/L; p = 0.001) and handcycling (10.6 ̆ 2.5 and 9.2 ̆ 2.9 mmol/L; p = 0.006)
Lower peripheral ratings of perceived exertion (RPE) were reported at 20 min during cycling and at 30 min during handcycling, and lower central RPE was seen at 30 min during cycling (p < 0.05)
Summary
Low-moderate doses of caffeine (3–6 mg per kilogram of body weight (mgkg1 )) have been shown to positively influence cycling time-trial (TT) performance [1,2]. The leg musculature provides the speed-generating force. There are numerous sports and activities such as kayaking, handcycling, double-poling and wheelchair sports during which the arms produce this force. The physiological responses to whole- and lower-body exercise (LBE) differ to those of UBE [6], and it is debatable whether the findings from the aforementioned cycling studies are transferable to an UBE sport such as handcycling. A potential mechanism of caffeine is its influence on the central nervous system (CNS) by which it acts as an adenosine receptor (most likely A1 and A2a ) antagonist [7,8]. Antagonism reduces the influence of adenosine and produces motor-activating and arousing effects. Caffeine can Nutrients 2016, 8, 393; doi:10.3390/nu8070393 www.mdpi.com/journal/nutrients
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