Macronutrient supplementation for endurance athletes

Purpose: The present study addressed two questions related to macronutrient supplementation during endurance exercise. Firstly, the effects of carbohydrate and protein co-ingestion on time trial (TT) performance were compared to carbohydrate alone. Secondly, the effects of isolated protein ingestion on TT performance were compared to a placebo. Methods: Six trained cyclists (Age: 22 ± 1 years; Height: 167 ± 12 cm; Weight: 60 ± 10 kg; VO2max: 62 ± 7 ml/kg/min) completed four experimental trials, consisting of constant-load cycling for two hours (55% Wmax) immediately followed by a 30-km simulated time trial. During the trials, subjects consumed one of four experimental beverages at regular intervals during exercise: a non-caloric placebo (PL), a protein-only beverage (PR: 15 g/hr), a carbohydrate-only beverage (45 g/hr), or a carbohydrate and protein beverage (CP: 45 g/hr CHO + 15 g/hr PRO). Physiological measurements (VO2, VE, HR, RER, blood glucose, and blood lactate) and subjective measurements (GI distress and RPE) were assessed throughout both the constant-load and TT exercise phases. Trials were completed in a randomly-counterbalanced order. Mean ± 90% confidence intervals were calculated for all measures, and magnitude-based qualitative inferences were used to assess treatment effects. Results: In comparison to PL (62.8 ± 8.1 min), both CHO and CP provided ‘possible’ benefits in TT performance (58.9 ± 6.5 min; 59.2 ± 9.4 min respectively) while no clear effects of PRO on performance were observed (61.0 ± 8.0 min). Furthermore, CP had no clear effect on performance versus CHO. Conclusions: In our sample, the addition of protein to a moderate-dose of carbohydrate did not result in meaningful improvements in time trial performance versus carbohydrate alone. Similarly, protein consumption alone provided no ergogenic effects versus a placebo

Agreement Between the Stages Cycling and SRM Powermeter Systems during Field-Based Off-Road Climbing.

The aim of this study was to determine the agreement between two portable cycling powermeters for use doing field based mountain biking. A single participant performed 15 timed ascents of an off-road climbs. The participants bicycle was instrumented with Stages Cycling and SRM powermeters. Mean and peak power output and cadence were recorded at 1 s intervals by both systems. Significant differences were determined using paired t-tests, whilst agreement was determined using 95% ratio limits of agreement (LoA). Significant differences were found between the two systems for mean power output (p<.001), with the Stages powermeter under reporting power by 8 % compared to the SRM. LoA for mean power output were 0.92 ×÷ 1.02 (95% LoA = 0.90 – 0.93). Peak power output was also significantly lower with the Stages powermeter (p=.02) by 5 % when compared to the SRM powermeter. LoA for peak power output were 0.94 ×÷ 1.09 (95% limits of agreement = 0.87 – 1.03). Significant differences were found for mean cadence between the two powermeters (p=.009), with LoA being 0.99 ×÷ 1.01 (95% limits of agreement = 0.99 – 1.00). This study found that though the Stages Cycling powermeter provided a reliable means of recording power output and cadence, the system significantly underestimated mean and peak power output when compared with the SRM system. This may in part be due to differences in strain gauge configuration and the subsequent algorithms used in the calculation of power output and the potential influence of bilateral imbalances within the muscles may have on these calculations

Influence of Absolute versus relative L-arginine Dosage on 1 km and 16.1 km time trial performance in trained cyclists.

This investigation aimed to determine the effects of L-arginine supplementation on cycling time trial (TT) performance. Eight trained male cyclists performed 1 and 16.1km time trials on three occasions, control (CON), absolute (ABS) and relative (REL) loading. Participants consumed 500ml of water with either 6g (ABS), 0.15 g·kg-1 body mass (REL) of L-arginine or water (CON) 90min prior to testing. Time to completion, mean power output (Wmean) and post-exercise lactate (La) were recorded for each TT. Time to completion decreased non-significantly for 1 and 16.1km TT’s during ABS and REL trials compared to CON. Wmean was significantly different between CON and REL during 16.1 km TT (196.19 ± 32.40W and 215.81 ± 31.56W). Blood lactates was significantly different between CON and ABS for the 1 km TT (p = 0.04) (13.59 ± 1.21 mmol·L-1 and 12.38 ± 0.70 mmol·L-1, respectively) and between CON and ABS (p = 0.04) (9.11 ± 2.91mmol·L-1 and 7.64 ± 3.01mmol·L-1, respectively) and CON and REL (9.11 ± 2.91mmol·L-1 and 7.15 ± 2.96mmol·L-1, respectively) for 16.1km TT. These results indicate L-arginine supplementation does not significantly improve cycling TT performance, though there was a trend towards reduced time to completion and increased mean power output, and that relative doses appear more effective than absolute doses

Influence of Course Type on Upper Body Muscle Activity in Elite Cross-Country and Downhill Mountain Bikers During Off Road Downhill Cycling

This study aimed to investigate upper body muscle activity using surface electromyography (sEMG) in elite cross-country (XCO) and downhill (DH) cyclists during off road descending and the influence of man-made (MM) and natural terrain (NT) descents on muscle activity. Twelve male elite mountain bikers (n=6 XCO; age 23 ± 4 yrs; stature 180.5 ± 5.6 cm; body mass 70.0 ± 6.4 kg and n=6 DH; age 20 ± 2 yrs; stature 178.8 ± 3.1 cm; body mass 75.0 ± 3.0 kg) took part in this study. sEMG were recorded from the left biceps brachii, triceps brachii, latissimus dorsi and brachioradialis muscles and expressed as a percentage of maximal voluntary isometric contraction (% MVIC). Both groups performed single runs on different MM and NT courses specific to their cycling modality. Significant differences in mean % MVIC were found between biceps brachii and triceps brachii (p=.016) and triceps brachii and latissimus dorsi (p=.046) during MM descents and between biceps brachii and triceps brachii (p=.008) and triceps brachii and latissimus dorsi (p=.031) during NT descents within the DH group. Significant differences in mean % MVIC were found between biceps brachii and brachioradialis (p=.022) for MM runs and between biceps brachii and brachioradialis (p=.013) for NT runs within the XCO group. Upper body muscle activity differs according to the type of downhill terrain, and appears to be specific to DH and XCO riders. Therefore, the discipline specific impact on muscle activation and the type of course terrain ridden should be considered when mountain bikers engage in upper body conditioning programmes

Making Savers Winners: An Overview of Prize-Linked Saving Products

For over three centuries and throughout the globe, people have enthusiastically bought savings products that incorporate lottery elements. In lieu of paying traditional interest to all investors proportional to their balances, these Prize Linked Savings (PLS) accounts distribute periodic sizeable payments to some investors using a lottery-like drawing where an investor’s chances of winning are proportional to one’s account balances. This paper describes these products, provides examples of their use, argues for their potential popularity in the United States —especially to low and moderate income non-savers—and discusses the laws and regulations in the United States that largely prohibit their issuance