This manuscript describes three-dimensional force data collected during postural shifts performed by individuals simulating rock-climbing skills. Starting from a quadrupedal vertical posture, 6 expert climbers had to release their right-hand holds and maintain the tripedal posture for a few seconds. The vertical and contact forces (lateral and anteroposterior forces) applied on the holds were analyzed in two positions: an “imposed” position (the trunk far from the supporting wall) and an “optimized” position (the trunk close to the wall and lower contact forces at the holds). The tripedal postures performed in the two positions were achieved by the same pattern of vertical and contact forces exerted by the limbs on the holds. In the optimized position, the transfer of the forces was less extensive than in the imposed position, so that the forces were exerted primarily on the ipsilateral hold. Moreover, a link between the contact force values and the couple due to body weight with respect to the feet was shown.
Franck Quaine, Luc Martin and Jean-Pierre Blanchi
Nicolas Termoz, Luc Martin and François Prince
The aim of this study was to assess postural response efficiency to a self-initiated perturbation using an original method based on the inverted pendulum model. Eight young subjects were asked to perform bilateral arm raising and lowering at 3 different speeds while standing on a force plate. The time necessary to recover a steady state following the movement was computed by analyzing the time evolution of the coefficient of determination between the center of pressure and center of mass difference variable (COP-COM) and the horizontal acceleration of the COM. Results show a spatial reorganization (hip strategy) of the segments following the perturbation and a strong influence of the linear relationship to the arm velocity. However, the conditions of arm velocity did not have any effect on the time response of the postural control, suggesting that this parameter would be an invariant characteristic of the movement. These results support the existence of an internal representation of the inertial constraints related to the movement execution.
Naomi M. Cermak, Martin J. Gibala and Luc J.C. van Loon
Six days of dietary nitrate supplementation in the form of beetroot juice (~0.5 L/d) has been reported to reduce pulmonary oxygen uptake (VO2) during submaximal exercise and increase tolerance of high-intensity work rates, suggesting that nitrate can be a potent ergogenic aid. Limited data are available regarding the effect of nitrate ingestion on athletic performance, and no study has investigated the potential ergogenic effects of a small-volume, concentrated dose of beetroot juice. The authors tested the hypothesis that 6 d of nitrate ingestion would improve time-trial performance in trained cyclists. Using a double-blind, repeated-measures crossover design, 12 male cyclists (31 ± 3 yr, VO2peak = 58 ± 2 ml · kg−1 · min−1, maximal power [Wmax] = 342 ± 10 W) ingested 140 ml/d of concentrated beetroot (~8 mmol/d nitrate) juice (BEET) or a placebo (nitrate-depleted beetroot juice; PLAC) for 6 d, separated by a 14-d washout. After supplementation on Day 6, subjects performed 60 min of submaximal cycling (2 × 30 min at 45% and 65% Wmax, respectively), followed by a 10-km time trial. Time-trial performance (953 ± 18 vs. 965 ± 18 s, p < .005) and power output (294 ± 12 vs. 288 ± 12 W, p < .05) improved after BEET compared with PLAC supplementation. Submaximal VO2 was lower after BEET (45% Wmax = 1.92 ± 0.06 vs. 2.02 ± 0.09 L/min, 65% Wmax 2.94 ± 0.12 vs. 3.11 ± 0.12 L/min) than with PLAC (main effect, p < .05). Wholebody fuel selection and plasma lactate, glucose, and insulin concentrations did not differ between treatments. Six days of nitrate supplementation reduced VO2 during submaximal exercise and improved time-trial performance in trained cyclists.
Milou Beelen, Louise M. Burke, Martin J. Gibala and Luc J.C. van Loon
During postexercise recovery, optimal nutritional intake is important to replenish endogenous substrate stores and to facilitate muscle-damage repair and reconditioning. After exhaustive endurance-type exercise, muscle glycogen repletion forms the most important factor determining the time needed to recover. Postexercise carbohydrate (CHO) ingestion has been well established as the most important determinant of muscle glycogen synthesis. Coingestion of protein and/or amino acids does not seem to further increase muscle glycogensynthesis rates when CHO intake exceeds 1.2 g · kg−1 · hr−1. However, from a practical point of view it is not always feasible to ingest such large amounts of CHO. The combined ingestion of a small amount of protein (0.2–0.4 g · (0.2−0.4 g · kg−1 · hr−1) with less CHO (0.8 g · kg−1 · hr−1) stimulates endogenous insulin release and results in similar muscle glycogen-repletion rates as the ingestion of 1.2 g · kg−1 · hr−1 CHO. Furthermore, postexercise protein and/or amino acid administration is warranted to stimulate muscle protein synthesis, inhibit protein breakdown, and allow net muscle protein accretion. The consumption of ~20 g intact protein, or an equivalent of ~9 g essential amino acids, has been reported to maximize muscle protein-synthesis rates during the first hours of postexercise recovery. Ingestion of such small amounts of dietary protein 5 or 6 times daily might support maximal muscle protein-synthesis rates throughout the day. Consuming CHO and protein during the early phases of recovery has been shown to positively affect subsequent exercise performance and could be of specific benefit for athletes involved in multiple training or competition sessions on the same or consecutive days.
Jennifer R. Tomasone, Natascha N. Wesch, Kathleen A. Martin Ginis and Luc Noreau
Individuals with spinal cord injury (SCI) tend to report poorer quality of life (QOL) than people without a physical disability. Leisure-time physical activity (LTPA) has been shown to improve the QOL of people with and without disabilities and chronic conditions. The purpose of this systematic review was to examine the LTPA-QOL relationship among people with SCI by focusing on both objective and subjective QOL for both global QOL and domain-specifc (physical, psychological, social) QOL. Results suggest that LTPA is significantly associated with increases in both objective and subjective QOL in global QOL and all three QOL domains, with relatively few studies demonstrating a negative or nonsignificant relationship. Recommendations for future QOL research and interventions are discussed.
Jorn Trommelen, Milou Beelen, Marjan Mullers, Martin J. Gibala, Luc J.C. van Loon and Naomi M. Cermak
Carbohydrate mouth rinsing during exercise has been suggested to enhance performance of short (45–60 min) bouts of high-intensity (>75% VO2peak) exercise. Recent studies indicate that this performance enhancing effect may be dependent on the prandial state of the athlete. The purpose of this study was to define the impact of a carbohydrate mouth rinse on ~1-hr time trial performance in both the fasted and fed states. Using a double-blind, crossover design, 14 trained male cyclists (27 ± 6 years; 5.0 ± 0.5 W·kg−1) were selected to perform 4 time trials of ~1 hr (1,032 ± 127 kJ) on a cycle ergometer while rinsing their mouths with a 6.4% sucrose solution (SUC) or a noncaloric sweetened placebo (PLA) for 5 s at the start and at every 12.5% of their set amount of work completed. Two trials were performed in an overnight fasted state and two trials were performed 2 h after consuming a standardized breakfast. Performance time did not differ between any of the trials (fasted-PLA: 68.6 ± 7.2; fasted-SUC: 69.6 ± 7.5; fed-PLA: 67.6 ± 6.6; and fed-SUC: 69.0 ± 6.3 min; Prandial State × Mouth Rinse Solution p = .839; main effect prandial state p = .095; main effect mouth rinse solution p = .277). In line, mean power output and heart rate during exercise did not differ between trials. In conclusion, a sucrose mouth rinse does not improve ~1-hr time trial performance in well-trained cyclists when performed in either the fasted or the fed state.
A. Justine Dowd, Toni Schmader, Benjamin D. Sylvester, Mary E. Jung, Bruno D. Zumbo, Luc J. Martin and Mark R. Beauchamp
The objective of the studies presented in this paper was to examine whether the need to belong can be used to enhance exercise cognitions and behavior. Two studies examined the effectiveness of framing exercise as a means of boosting social skills (versus health benefits) for self-regulatory efficacy, exercise intentions, and (in Study 2) exercise behavior. In Study 1, inactive adults primed to feel a lack of social belonging revealed that this manipulation led to greater self-regulatory efficacy (but not exercise intentions). In Study 2, involving a sample of inactive lonely adults, all participants reported engaging in more exercise; however, those in the social skills condition also reported a greater sense of belonging than those in the health benefits comparison condition. These findings provide an important basis for developing physical activity interventions that might be particularly relevant for people at risk for feeling socially isolated or lonely.
Naomi M. Cermak, Peter Res, Rudi Stinkens, Jon O. Lundberg, Martin J. Gibala and Luc J.C. van Loon
Dietary nitrate supplementation has received much attention in the literature due to its proposed ergogenic properties. Recently, the ingestion of a single bolus of nitrate-rich beetroot juice (500 ml, ~6.2 mmol NO3−) was reported to improve subsequent time-trial performance. However, this large volume of ingested beetroot juice does not represent a realistic dietary strategy for athletes to follow in a practical, performancebased setting. Therefore, we investigated the impact of ingesting a single bolus of concentrated nitrate-rich beetroot juice (140 ml, ~8.7 mmol NO3−) on subsequent 1-hr time-trial performance in well-trained cyclists.
Using a double-blind, repeated-measures crossover design (1-wk washout period), 20 trained male cyclists (26 ± 1 yr, VO2peak 60 ± 1 ml · kg−1 · min−1, Wmax 398 ± 7.7 W) ingested 140 ml of concentrated beetroot juice (8.7 mmol NO3−; BEET) or a placebo (nitrate-depleted beetroot juice; PLAC) with breakfast 2.5 hr before an ~1-hr cycling time trial (1,073 ± 21 kJ). Resting blood samples were collected every 30 min after BEET or PLAC ingestion and immediately after the time trial.
Plasma nitrite concentration was higher in BEET than PLAC before the onset of the time trial (532 ± 32 vs. 271 ± 13 nM, respectively; p < .001), but subsequent time-trial performance (65.5 ± 1.1 vs. 65 ± 1.1 s), power output (275 ± 7 vs. 278 ± 7 W), and heart rate (170 ± 2 vs. 170 ± 2 beats/min) did not differ between BEET and PLAC treatments (all p > .05).
Ingestion of a single bolus of concentrated (140 ml) beetroot juice (8.7 mmol NO3−) does not improve subsequent 1-hr time-trial performance in well-trained cyclists.