ANTIOXIDANTS

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Relevant to previous discussions on the list:

DO ANTIOXIDANTS ENHANCE OR SUPPRESS TRAINING INDUCED ADAPTATIONS?

PHILP, A.

UNIVERSITY OF DUNDEE

14th annual Congress of the

EUROPEAN COLLEGE OF SPORT SCIENCE

Oslo/Norway, June 24-27, 2009

BOOK OF ABSTRACTS

Exercise involves a complex series of cellular events, which combine to mediate

skeletal muscle adaptation. Muscle contraction evokes

signal transduction pathways regulated by calcium and ATP fluctuations as well

as a stress response leading to systemic release of

hormones, and the muscle specific generation of reactive oxygen species and

cytokines. As a general process, this response can be

termed exercise specific inflammation and recent research suggests that this

transient inflammatory response is a key factor in exercise

adaptation (sen and Pedersen, 2005). If inflammation is prolonged however,

such as during repetitive periods of intense training, or

sustained exhaustive exercise, deleterious effects develop within the working

muscle suggesting that the range over which inflammation

is beneficial is small. Radicals and reactive oxygen species (ROS) are molecules

that initiate damaging oxidation reactions within the cell

(Powers et al., 2004). ROS generation has been linked with exercise induced

oxidative injury and muscle fatigue due to an imbalance

between oxidant production and the antioxidant capacity of the cell (Powers and

, 2008). There are a number of enzymatic and

non-enzymatic defence systems, or antioxidants, in mammalian skeletal muscle

which reduce free radicals and reactive oxygen species

production. Importantly, dietary antioxidants work in synergy with these

endogenous antioxidants to offset ROS induced oxidative stress.

With this in mind, recreational and elite athletes supplement with antioxidant

agents, in the belief that they will protect the athlete against

exercise-induced damage, local inflammation and enhance post exercise recovery.

However, recent research suggests that dietary

antioxidants may in fact suppress ROS mediated signalling essential for

exercise-induced adaptation (Powers and , 2008). Specifically

it appears that ROS generation is important for kinase activity of the

AMP-dependent kinase (AMPK), the mitogen activated protein

kinases (p38 and p42/44) and their downstream targets NF- & #954;B and the

transcriptional co-activator PGC-1á (Gomez-Cabrera et al.,

2005; Irrcher et al., 2009). Therefore, whether antioxidants enhance or

interfere with training adaptation and whether training regimes

and nutritional interventions should be adjusted to account for ROS action in

response to exercise remains a controversial issue.

References

sen, AM and Pedersen, BK (2005) J. Appl. Physiol. 98(4): 1154-62.

Powers, SK et al., (2004) J. Sports Sciences. 22: 81-94.

Powers, SK and , MJ (2008) Physiol. Rev. 88: 1243-76

Gomez-Cabrera, M-C et al., (2005) J. Physiol. 567.1: 113-20

Irrcher, I et al., (2009) Am. J. Physiol. Cell Physiol. 296: C116-23

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Carruthers

Wakefield, UK