Consumption of low glycemic index (GI) foods before submaximal endurance exercise may be beneficial to performance. To test whether this may also be true for high intensity exercise. 10 trained cyclists began an incremental exercise test to exhaustion 65 min after consuming equal carbohydrate portions of glucose (HGI), pasta (LGI), and a noncarbohydrate control (PL). Time to fatigue did not differ significantly (p = 0.05) between treatments. Plasma glucose concentration was significantly lower after LGI vs. HGI from 15 to 45 min of rest postprandial. During exercise, plasma glucose concentration was significantly lower after HGI vs. LGI from 200 W until exhaustion. Plasma lactate concentration following HGI was significantly higher than PL from 30 min of rest postprandial through to the end of the 200-W workload. Plasma lactate concentration following LGI was significantly lower than after HGI from 45 min of rest postprandial through to the end of the 100-W workload. At higher exercise intensities, there was no significant difference in plasma lactate levels between treatments. These findings suggest that a high GI carbohydrate meal (1 g/kg body wt) 65 min prior to exercise decreases plasma glucose and increases plasma lactate levels compared to a low GI meal, but not enough to be detrimental to incremental exercise performance.
Stephen R. Stannard, Martin W. Thompson and Janette C. Brand Miller
Sandra K. Hunter, Martin W. Thompson and Roger D. Adams
The purposes of this study were to investigate the rate of change with age of simple lower-limb reaction time (RT) in women and determine the relationship among RT. strength, and physical activity. Independent, community-dwelling women aged 20–89 years (N = 217) were assessed for knee-extension RT, maximal voluntary isometric contractions of the knee extensors (KE), and physical activity level. Trend analysis by ANOVA and regression analysis on RT were performed. Lower-limb RT increased and KE strength and physical activity level decreased linearly across age groups (p < .001). Active women had faster RTs than those of inactive women of the same age (p < .01). From multiple-regression analysis on RT, only 1 predictor variable. KE strength, emerged. Stronger women had faster RTs than those of weaker women (p < .0001), regardless of age and physical activity. Although RT was slower in older women, higher levels of strength and physical activity were associated with faster RTs in this group.
Kieran E. Fallon, Elizabeth Broad, Martin W. Thompson and Patricia A. Reull
The fluid and food intakes of 7 male participants in a 100-km ultramarathon were recorded. The mean exercise time was 10 hr 29 min. Nutrient analysis revealed a mean inlrarace energy intake of 4.233 kJ. with 88.6% derived from carbohydrate. 6.7% from fat, and 4.7% from protein. Fluid intake varied widely. 3.3–1 1.1 L, with a mean of 5.7 L. The mean decrease in plasma volume at 100 km was 7.3%, accompanied by an estimated mean sweat rale of 0.86 L ⋅ hr−1. Blood glucose concentrations remained normal during the event, and free fatty acids and glycerol were elevated both during and at the conclusion of the event. No significant correlations were found between absolute amounts and rates of ingestion of carbohydrate and/or fluid and race performance.
Saied Jalal Aboodarda, Ashril Yusof, N.A. Abu Osman, Martin W. Thompson and A. Halim Mokhtar
To identify the effect of additional elastic force on the kinetic and kinematic characteristics, as well as the magnitude of leg stiffness, during the performance of accentuated countermovement jumps (CMJs).
Fifteen trained male subjects performed 3 types of CMJ including free CMJ (FCMJ; ie, body weight), ACMJ-20, and ACMJ-30 (ie, accentuated eccentric CMJ with downward tensile force equivalent to 20% and 30% body mass, respectively). A force platform synchronized with 6 high-speed infrared cameras was used to measure vertical ground-reaction force (VGRF) and displacement.
Using downward tensile force during the lowering phase of a CMJ and releasing the bands at the start of the concentric phase increased maximal concentric VGRF (6.34%), power output (23.21%), net impulse (16.65%), and jump height (9.52%) in ACMJ-30 compared with FCMJ (all P < .05). However, no significant difference was observed in the magnitude of leg stiffness between the 3 modes of jump. The results indicate that using downward recoil force of the elastic material during the eccentric phase of a CMJ could be an effective method to enhance jump performance by applying a greater eccentric loading on the parallel and series elastic components coupled with the release of stored elastic energy.
The importance of this finding is related to the proposition that power output, net impulse, takeoff velocity, and jump height are the key parameters for successful athletic performance, and any training method that improves impulse and power production may improve sports performance, particularly in jumping aspects of sport.