Improvements in exercise performance: effects of carbohydrate feedings and diet

Abstract

In an effort to determine the effects of carbohydrate (CHO) feedings immediately before exercise in both the fasted and fed state, 10 well-trained male cyclists [maximum O2 consumption (VO2 max), 4.35 +/- 0.11 l/min)] performed 45 min of cycling at 77% VO2 max followed by a 15-min performance ride on an isokinetic cycle ergometer. After a 12-h fast, subjects ingested 45 g of liquid carbohydrate (LCHO), solid carbohydrate confectionery bar (SCHO), or placebo (P) 5 min before exercise. An additional trial was performed in which a high-CHO meal (200 g) taken 4 h before exercise was combined with a confectionery bar feeding (M + SCHO) immediately before the activity. At 10 min of exercise, serum glucose values were elevated by 18 and 24% during SCHO and LCHO, respectively, compared with P. At 0 and 45 min no significant differences were observed in muscle glycogen concentration or total use between the four trials. Total work produced during the final 15 min of exercise was significantly greater (P less than 0.05) during M + SCHO (194,735 +/- 9,448 N X m), compared with all other trials and significantly greater (P less than 0.05) during LCHO and SCHO (175,204 +/- 11,780 and 176,013 +/- 10,465 N X m, respectively) than trial P (159,143 +/- 11,407 N X m). These results suggest that, under conditions when CHO stores are less than optimal, exercise performance is enhanced with the ingestion of 45 g of CHO 5 min before 1 h of intense cycling.(ABSTRACT TRUNCATED AT 250 WORDS)

Improved Gross Efficiency during Long Duration Submaximal Cycling Following a Short-term High Carbohydrate Diet

“…The results presented indicate that a high carbohydrate intake in the three days prior to an exercise assessment increased the efficiency values of trained cyclists by ~4% compared to moderate carbohydrate conditions. These results support the data presented by Jansson [20], Neufer et al, [27] and Dumke et al, [8] who reported alterations in exercise efficiency scores with altered carbohydrate status. As these previous studies utilizsed time to exhaustion tests, their data isare limited for the purposes of calculating GE due to fatigue related reductions in the exercise intensity as the trials progressed.…”

“…Unfortunately, these early papers did not maintain the exercise intensity during their experimental protocols, and as time elapsed and fatigue ensued, the work rates were altered between trials. Altering work rates has been shown to influence the efficiency values obtained [6,11,30], therefore limiting the application of both Jansson and Neufer et al, [20,27]. Additionally, the later work of Dumke et al, [8] alluded to altered efficiency values with nutritional intervention but likewise did not maintain exercise intensity across different conditions.…”

“…This is somewhat problematic because early papers in this field have reported differences in cycling efficiency with altered carbohydrate intake during the period leading up to assessment [20,27]. Unfortunately, these early papers did not maintain the exercise intensity during their experimental protocols, and as time elapsed and fatigue ensued, the work rates were altered between trials.…”

The effect of breakfast on appetite regulation, energy balance and exercise performance

“…Whilst individuals concerned purely with weight management may not be overly concerned about carbohydrate availability, consuming adequate carbohydrate is of primary importance to individuals wanting to maximise athletic performance (55,56) . Several studies have demonstrated that consumption of carbohydrate in the morning can improve exercise performance compared with performing exercise in the overnight fasted state (57)(58)(59)(60)(61)(62)(63) . However, the majority of these studies provided carbohydrate drinks rather than a typical breakfast meal, and therefore may not accurately represent breakfast consumption and omission per se.…”

Fuel kinetics during intense running and cycling when fed carbohydrate

“…The effect of carbohydrate (CHO) ingestion on energy metabolism and endurance capacity during prolonged (>90 min), low-to-moderate intensity (55-70% of maximal oxygen uptake [V0 2 maxn exercise has largely been studied in cyclists protocols (Coggan & Coyle 1988, 1989Coyle et al 1983Coyle et al , 1986Flynn et al 1987;Ivy et al 1983;Neufer et al 1987;Hawley et al 1992a & b;Rauch et al 1995). Only a few groups have examined fuel kinetics during running (Wilber & Moffat 1992;Madsen et al 1990;Tsintzas et al 1993a,b).…”