Time Trials

Byrne C, Owen C, Cosnefroy A, & Lee JK.
J Athl Train. 2011 Nov-Dec;46(6):592-9.

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CONTEXT: Precooling is the pre-exercise reduction of body temperature and is an effective method of improving physiologic function and exercise performance in environmental heat. A practical and effective method of precooling suitable for application at athletic venues has not been demonstrated.

OBJECTIVE: To confirm the effectiveness of pre-exercise ingestion of cold fluid without fluid ingestion during exercise on pre-exercise core temperature and to determine whether pre-exercise ingestion of cold fluid alone without continued provision of cold fluid during exercise can improve exercise performance in the heat.

DESIGN: Randomized controlled clinical trial.

SETTING: Environmental chamber at an exercise physiology laboratory that was maintained at 32°C, 60% relative humidity, and 3.2 m/s facing air velocity.

PATIENTS OR OTHER PARTICIPANTS: Seven male recreational cyclists (age = 21 ± 1.5 years, height = 1.81 ± 0.07 m, mass = 78.4 ± 9.2 kg) participated.

INTERVENTION(S): Participants ingested 900 mL of cold (2°C) or control (37°C) flavored water in 3 300-mL aliquots over 35 minutes of pre-exercise rest.

MAIN OUTCOME MEASURE(S): Rectal temperature and thermal comfort before exercise and distance cycled, power output, pacing, rectal temperature, mean skin temperature, heart rate, blood lactate, thermal comfort, perceived exertion, and sweat loss during exercise.

RESULTS: During rest, a greater decrease in rectal temperature was observed with ingestion of the cold fluid (0.41 ± 0.16°C) than the control fluid (0.17 ± 0.17°C) over 35 to 5 minutes before exercise (t(6) = -3.47, P = .01). During exercise, rectal temperature was lower after ingestion of the cold fluid at 5 to 25 minutes (t(6) range, 2.53-3.38, P ≤ .05). Distance cycled was greater after ingestion of the cold fluid (19.26 ± 2.91 km) than after ingestion of the control fluid (18.72 ± 2.59 km; t(6) = -2.80, P = .03). Mean power output also was greater after ingestion of the cold fluid (275 ± 27 W) than the control fluid (261 ± 22 W; t(6) = -2.13, P = .05). No differences were observed for pacing, mean skin temperature, heart rate, blood lactate, thermal comfort, perceived exertion, and sweat loss (P > .05).

CONCLUSIONS: We demonstrated that pre-exercise ingestion of cold fluid is a simple, effective precooling method suitable for field-based application.

The objective of the current research was to investigate the effect of calcium supplementation on cycling performance. Ten male well-trained cyclists (mean ± SD; age 35.8 ± 11.3 yrs, stature 176 ± 7.1 cm, body mass 73.8 ± 9.3 kg, VO2peak 4.59 ± 0.8 l/min, Wpeak 350 ± 42 W) were recruited. Participants were tested using a randomised, single blind, test-retest intervention trial design. Each participant was given 1000 mg/d of elemental calcium (citrate) in tablet form for 4 weeks. They undertook a 10 mile bicycle ergometer time trial test at baseline (10TTB) and end of the intervention period (10TTC). A stationary electromagnetically braked ergometer (SRM ergometer; Schoberer Rad Messtechnik, Jülich, Germany) was used. Gas exchange was measured continuously using an online breath-by-breath Spirometer (Metalyzer II; Cortex, Leipzig, Germany). There was a drop in time-to-finish (–0.20 ± 0.11 mins; P = 0.17, d = –0.18) and mean power output increased (7.22 ± 0.65 W; P = 0.02, d = 0.21) in 10TTC compared to 10TTB. Both mean gross efficiency (1.19 ± 0.40%; P = 0.001, d = 1.09) and mean economy (4.15 ± 1.41 W/l; P = 0.001, d = 0.82) improved significantly during the 10TTC compared to 10TTB. Increased dietary calcium may have improved performance via changes in intracellular calcium [Ca2+]i levels. Efficiency may have improved due to a combination of better utilisation of metabolic substrates and attenuated skeletal muscle fatigue.