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Comment le sport endommage t’il le coeur sur le long terme?

19/05/2016 | Etudes cardio et Echauffement et blessures et Etudes Anti-âge

 

Long-term leucine supplementation aggravates prolonged strenuous exercise-induced cardiovascular changes in trained rats
Gustavo Barbosa dos Santos             Experimental Physiology 2016

Observational studies have raised concerns that prolonged strenuous exercise training may be associated with increased risk of cardiac arrhythmia and even primary cardiac arrest or sudden death. It has been demonstrated that leucine can reduce prolonged exercise-induced muscle damage and accelerate the recovery process. The aim of this study was to investigate the effects of prolonged strenuous endurance exercise on cardiovascular parameters and biomarkers of cardiac injury in trained adult male rats and assess the use of leucine as an auxiliary substance to prevent the likely cardiac adverse effects caused by strenuous exercise. Twenty-four male Wistar rats were randomly allocated to receive a balanced control diet (18% protein) or a leucine-rich diet (15% protein plus 3% leucine) for 6 weeks. The rats were submitted to 1 hour of exercise, 5 d.wk−1 for 6 wk. Three days after the training period rats were submitted to swimming exercises until exhaustion and cardiac parameters were assessed.

Exercising until exhaustion significantly increased cardiac biomarker levels and cytokines, glycogen content and inhibited protein synthesis signaling also led to cardiac electrical disturbances. When combined with exercise, leucine supplementation led to further increases in the aforementioned parameters and also significant increase in blood pressure and protein degradation signaling. We report, for the first time, that leucine supplementation not only does not prevent cardiac fatigue symptoms, but may also aggravate prolonged strenuous exercise-induced cardiovascular disturbances in trained rats. Furthermore, we find that exercising until exhaustion can cause cardiac electrical disturbances and cardiac myocyte damage.

Le rameur brûle plus de gras que le vélo

07/05/2016 | Etudes cardio et Etudes Perte de poids

 

Higher rate of fat oxidation during rowing compared with cycling ergometer exercise across a range of exercise intensities
B. Egan           Scandinavian Journal of Medicine & Science in Sports Volume 26, Issue 6, pages 630–637, June 2016

The relative contribution of carbohydrate and fat oxidation to energy expenditure during exercise is dependent on variables including exercise intensity, mode, and recruited muscle mass. This study investigated patterns of substrate utilization during two non-weightbearing exercise modalities, namely cycling and rowing. Thirteen young, moderately trained males performed a continuous incremental (3-min stages) exercise test to exhaustion on separate occasions on an electronically braked cycle (CYC) ergometer and an air-braked rowing (ROW) ergometer, respectively. On two further occasions, participants performed a 20-min steady-state exercise bout at ∼50%VO2peak on the respective modalities.

Despite similar oxygen consumption, rates of fat oxidation (FATox) were ∼45% higher during ROW compared with CYC (P 

< 0.05) across a range of power output increments.

The crossover point for substrate utilization occurred at a higher relative exercise intensity for ROW than CYC (57.8 ± 2.1 vs 42.1 ± 3.6%VO2peak, P < 0.05). During steady-state submaximal exercise, the higher FATox during ROW compared with CYC was maintained (P < 0.05), but absolute FATox were 42% (CYC) and 28% (ROW) lower than during incremental exercise.

FATox is higher during ROW compared with CYC exercise across a range of exercise intensities matched for energy expenditure, and is likely as a consequence of larger muscle mass recruited during ROW.

Le simple gout de la caféine augmente la performance, surtout le matin

07/05/2016 | Etudes Compléments alimentaires et Etudes Perte de poids

 

Caffeine and 3-km cycling performance: Effects of mouth rinsing, genotype, and time of day
M. W. Pataky               Scandinavian Journal of Medicine & Science in Sports       Volume 26, Issue 6, pages 613–619, June 2016

We assessed the efficacy of caffeine mouth rinsing on 3-km cycling performance and determined whether caffeine mouth rinsing affects performance gains influenced by the CYP1A2 polymorphism. Thirty-eight recreational cyclists completed four simulated 3-km time trials (TT). Subjects ingested either 6 mg/kg BW of caffeine or placebo 1 h prior to each TT. Additionally, 25 mL of 1.14% caffeine or placebo solution were mouth rinsed before each TT. The treatments were Placebo, caffeine Ingestion, caffeine Rinse and Ingestion+Rinse. Subjects were genotyped and classified as AA homozygotes or AC heterozygotes for the rs762551 polymorphism of the CYP1A2 gene involved in caffeine metabolism. Magnitude-based inferences were used to evaluate treatment differences in mean power output based on a predetermined meaningful treatment effect of 1.0%. AC heterozygotes (4.1%) and AA homozygotes (3.4%) benefited from Ingestion+Rinse, but only AC performed better with Ingestion (6.0%).

Additionally, Rinse and Ingestion+Rinse elicited better performance relative to Placebo among subjects that performed prior to 10:00 h (Early) compared with after 10:00 h (Late).

The present study provides additional evidence of genotype and time of day factors that affect the ergogenic value of caffeine intake that may allow for more personalized caffeine intake strategies to maximize performance.

Les bouteilles en plastiques préservent moins les vitamines des jus que le verre

11/04/2016 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Changes in nutritional value of a multi-vitamins fortified juice packed in glass and standard PET bottles
Food Control Volume 60, February 2016, Pages 256–262     Céline Bacigalupi

Highlights
• Nutritional properties of juice packed in glass or PET bottles.
• Ascorbic acid strongly decreases in presence of tocopherol.
• Regenerative action of ascorbic acid.
• Oxidation of carotenes in PET and isomerization in glass bottles.


The evolution of ascorbic acid, β-carotene and α-tocopherol contents was assessed during the storage of a fortified juice packed in PET or glass bottles. During the course of storage, oxygen transfer rates and partial oxygen pressures were evaluated as well as the vitamins.

During the first month, a decrease of dissolved oxygen was observed for both PET and glass bottles. A strong degradation of ascorbic acid was noted after 3 months of storage (up to 54 at 72% in glass and PET bottles respectively) and the β-carotene content was virtually nil after 80 days. The ascorbic acid degradation was clearly stronger in PET comparing to glass bottles while no difference was observed for β-carotene between both packaging. However, β-carotene isomers (13-cis-β-carotene and 9-cis-β-carotene) were identified and their total concentrations were higher in glass bottles. The degradation reaction scheme of β-carotene seems to be mainly oxidation in PET bottles and isomerisation and then oxidation in glass bottles. Concerning tocopherol, its limited oxidation may be explained by regenerative action of ascorbic acid.

From a nutritional point of view, the juice packed in glass bottles is more interesting since β-carotene isomers still have pro-vitamin activity.

La natation: pas super efficace dans la chasse au gras

01/04/2016 | Etudes cardio et Etudes Perte de poids et Etudes Anti-âge

 

HIGH INTENSITY CROSSFIT TRAINING COMPARED TO HIGH
INTENSITY SWIMMING: A PRE-POST TRIAL TO ASSESS THE
IMPACT ON BODY COMPOSITION, MUSCLE STRENGTH AND
RESTING ENERGY EXPENDITURE

S. Perna   Nutrition 32 (2016) 399–408


Introduction: The aim of this study was to evaluate the impact of
two high intensity training as different high intensity training, i.e.
power CrossFit and intermittent Swimming, on body composition
markers, max strength and resting energy expenditure.
Material and Methods: This pre-post trial was conducted in
Twenty-three subjects (14 female, 9 male; mean age ¼ 31.74 
7.46 years; BMI ¼ 23.665  2.994 kg/m2
). They were assigned to
intervention of CrossFit training or Swimming training (CrossFit/
Swimming: 10/13) for 8-weeks (60 min, 3 times per week). Using
Dual X ray Energy Absorptiometry, we measured body mass
composition markers. Muscle strength and resting energy
expenditure were measured at baseline and immediate after 8
weeks of training intervention. This variables were measured at
baseline and after 8 weeks.

Results: Between groups, data demonstrated a significant
changes on gynoid fat (-1.670 %; P¼0.024) in favour of CrossFit
training. Suggestive but not significant differences (0.05 <0.10) between groups in decreasing of Fat Mass (-1439 g;
P¼0.073) and Android Fat (-2.614%; P¼0.075), were found. The
pre-post differences within training interventions were signifi-
cant (P<0.05) for Fat mass, gynoid fat, free fat mass and Resting
Energy Expenditure (REE) in CrossFit group.

Conclusions: This study showed the potential benefits of High
Intensity Training in improvement on body composition markers.
In particular, CrossFit is more performing than swimming in
losses of total fat mass, specifically of gynoid and android fat mass.

Pas facile d’être végétarien!

12/03/2016 | Etudes Compléments alimentaires

 

THE EFFECTS OF A PRE-WORKOUT VEGAN SUPPLEMENT ON CYCLING PERFORMANCE LEVELS IN A SAMPLE OF COLLEGE AGED MALES
G. GALLIEN         Journal of Strength and Conditioning Research   2016 VOLUME 30 | SUPPLEMENT 1 | FEBRUARY | S86

Individuals who exercise and live a vegan lifestyle may
experience difficulty when trying to find an effective preworkout
supplement that does not contain any animal byproducts.
No previous studies have examined the relationship
between the use of a vegan supplement and exercise
performance levels.

Purpose: To examine the effects of
a vegan pre-workout supplement on cycling performance levels
in recreationally active college-aged men. Methods: Recreationally
active college-aged men (n = 14; age = 22 6 1.84
years; height = 178.99 6 8.69 cm; body mass = 78.53 6
11.61 kg) volunteered to participate in this study. Subjects
completed a familiarization trial, which consisted of a graded
exercise test, followed by 3 separate visits in which participants
exercised at a workload that represented 80% of their
V_ O2peak until exhaustion. Supplements were administered
using a randomized, double-blind cross-over design and
included (a) vegan pre-workout supplement (70 kcal), (b) an
isocaloric sports drink, and (c) a zero-calorie drink with artificial
sweetener. Each of the 3 exercise trails were separated by
a minimum of 72 hours. For each trial, participants completed
an overnight fast. Thirty minutes prior to testing, participants
consumed one of the 3 supplements mixed with 12 ounces of
water.

Results: The average time in seconds (s) until exhaustion
while using the vegan pre-workout supplement was 482 6
163 seconds. The average time until exhaustion while using the
isocaloric sports drink was 480 6 157 seconds. The average
time until exhaustion using the zero calorie drink was 496 6
238 seconds.

Conclusions: Consumption of the vegan supplement
provided no ergogenic benefit compared to an isocaloric
and zero-calorie drink
for recreationally-active males while
cycling at 80% of their V_ O2peak.

Practical Applications:
Since veganism has recently become a more popular practice,
there has been an increase in vegan-friendly products available
to consumers. The results of this study indicate that individuals
who choose a vegan pre-workout supplement (over an isocaloric
or zero-calorie product) will not experience any difference in
exercise performance. Although the present study does not support
the use of the tested vegan pre-workout supplement before
cycling, further research is warranted in this area.

L’entraînement au poids de corps ne serait-il que de la gonflette?

12/03/2016 | Etudes Musculation

 

MUSCLE ACTIVATION, MUSCLE SWELLING, AND EXERCISE VOLUME DURING THREE SETS TO FAILURE AT 80% VS. 30% 1RM RESISTANCE EXERCISE
N. JENKINS             Journal of Strength and Conditioning Research   2016   VOLUME 30 | SUPPLEMENT 1 | FEBRUARY | S47

However, it is unclear how muscle activation influences these adaptations.

Purpose: Therefore, the purpose of this study was to investigate electromyographic amplitude
(EMG AMP), EMG mean power frequency (MPF), muscle
cross sectional area (mCSA), exercise volume (VOL), total
work and muscle activation (iEMG), and time under concentric
tension (TUCT) during 3 sets to failure at 80% vs. 30% 1RM
leg extension resistance exercise in men and women.

Methods: Eleven men (mean 6 SD; age = 21.5 6 2.7 years; resistance
training per week = 6.6 6 3.7 hours) and 11 women
(age = 22.3 6 3.6 years; resistance training per week = 3.7 6
3.3 hours) completed 1RM testing, followed by 2 experimental
sessions during which they completed 3 sets to failure of leg
extension resistance exercise at 80 or 30% 1RM. EMG signals
were recorded from the 3 superficial quadriceps femoris
muscles of the dominant thigh. An electrogoniometer was
placed across the knee joint to measure joint angle (8). Exercises
were performed on a plate-loaded leg extension device
that was custom fitted with a load cell. Force, EMG AMP
(mV$s21), and EMG MPF (Hz) values were calculated from
signal epochs corresponding to the 608 range of motion occurring
between 1008 and 1608 of leg extension during the concentric
portion of each repetition (rep) based on the
electrogoniometer signal. The EMG AMP and MPF values from
the initial, middle, and last rep of each set were normalized to
a maximal voluntary isometric contraction (MVIC) and used for
analyses. Panoramic ultrasound imaging was used to assess
mCSA of the rectus femoris and vastus lateralis immediately
pre- and post-exercise. Exercise volume, total work, iEMG, and
TUCT were also quantified.

Results: The mean 6 SD for the
numbers of reps completed during sets 1, 2, and 3 were 8.9 6
2.7, 6.7 6 1.9, and 6.2 6 1.7 at 80% 1RM, and 45.6 6 14.3,
26.8 6 8.3, and 22.2 6 8.6 at 30% 1RM, respectively. EMG
AMP increased across reps and sets at 80 and 30% 1RM, but
was consistently greater for 80 than 30% 1RM. EMG MPF
decreased across reps at 80 and 30% 1RM, but decreased
to a greater extent and was lower for the last reps at 30 than
80% 1RM (71.6% vs. 78.1% MVIC). mCSA increased more
from pre-to post-exercise for 30% (20.2 cm2–24.1 cm2) than
80% 1RM (20.3 cm2–22.8 cm2). VOL, total work, iEMG and
TUCT were greater for 30 than 80% 1RM.

Conclusions: EMG AMP remained greater at 80 than 30% 1RM across all
repetitions and during all sets, despite 74 and 147% increases
in EMG AMP during the sets at 80 and 30% 1RM, respectively.
VOL, total work, iEMG, and TUCT were 18–202%
greater, and the decreases in EMG MPF were more pronounced
at 30% 1RM. Furthermore, the increases in mCSA
(i.e., muscle swelling) from pre-to post-exercise were greater at
30 than 80% 1RM.

Practical Applications: Muscle activation was greater during resistance exercise at 80 than 30% 1RM.
Therefore, muscle activation may not be responsible for the
similar hypertrophy observed after 30 vs. 80% 1RM training
to failure. Exercise volume, metabolic byproduct accumulation,
and muscle swelling, however, may be contributing factors.
Additional studies are needed to investigate the acute and
chronic neuromuscular responses to high-versus low-load
resistance training.

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