Welcome, this post on hydration status. First it should be noted that this blog post aims to service as a guide to current recommendations and in no way should be seen as a substitute for individual support from a qualified practitioner.
Fluid loss is experienced by athletes in all sports and can play a major part in the performance outcome of the event. Armstrong et al., (1985) found that a 2% loss in body mass can impair performance by 3-7%. This was supported by Maughan (1999) who found that a 5% loss in body mass can lead to a 30% drop in performance. If we do some simple maths based upon the final of the women’s cross country skiing free sprint, which I was lucky enough to attend last week, you can can see this issue can be the difference between winning medals.
Marit Bjoergen, the outstanding winner of the event, theoretically wouldn't have even made past heat 1 if she was dehydrated by just 3%. She had a winning time 3:04:8, therefore a 3% percentage loss of performance is equal to 5.54s, the person in last place in heat 1 was only 4.8s behind the winner! Marit would have gone from gold medal winner at the world championships to another name on the start list.
Therefore it is vital that athletes have a hydration plan which they follow. This will be dependent upon a number of factors however these are the key points to be noted:
General ~
- Women generally have lower sweating rates than men
- Children have lower sweating rate than adults
- Older adults have age related slower renal responses to water and may be at greater risk for hyponatremia
- Meal consumption promotes euhydration
- Alcohol consumption can increase urine output and delay rehydration
Pre-Exercise ~
- Measurement of body weight pre exercise.
- Consumption of fluid containing carbohydrates & electrolyte
Post-Exercise ~
- Measurement of body weight post exercise.
- Aim to replace every 1kg of body weight lost with 1.5l of fluid
- Sodium will help return to euhydrated state
Also it should be noted that monitoring hydration status is key to the success of any hydration plan. The easiest way to do this is to use the "pee test" which you compare the colour of your urine to chart such as the one below. Please feel free to email me if you would like a copy nicholasjones@dna-sports-performance.com
Written By Nicholas Jones DNA Sports Performance Director
Welcome, this post on muscle physiology as I have found myself discussing it with no end of my new athletes recently, so here goes...
Welcome, this post on muscle physiology as I have found myself discussing it with no end of my new athletes recently, so here goes...
The word muscle originates from the Latin word mus meaning ‘little mouse’, due to the appearance of the muscle when it is flexed (Marieb, 2003). When the word muscle is mentioned the picture of a defined bodybuilder usually comes to mind, however muscle plays a much more significant part in human function than for purely aesthetic purposes. Muscles are unique in that they can shorten (contract), a characteristic which sets it apart from any other bodily tissue (Marieb, 2003).
Contractions are responsible for all body movement and can be viewed as the ‘machines of the body’; muscles make up approximately 40% body’s mass (Edman, 2003). The body has three forms of muscle; cardiac, smooth and skeletal, each are organised into hundreds of separate entities or body muscles (Ward, 2004). Individual muscles are assigned specific tasks to enable the great variety of movements that are essential to all normal and sporting activities (Edman, 2003).
Macro Structure ~ The functions of the muscles are to produce movement, maintain posture, stabilise joints and generate heat (Marieb, 2003). Muscle has five basic characteristics as expressed by Ward (2004):
Excitability – the ability to respond to stimuli (nerve impulses or hormones)
- Conductivity – the ability to conduct nerve impulses along its length
- Contractility – the ability to contract (shorten and thicken) and thus produce force
- Extensibility – the ability to stretch or be stretched (within certain limits) without causing damage
- Elasticity – the ability to return to original shape following shortening or lengthening
Micro Structure ~ Each muscle is broken down into a cable like structures that are called ‘muscle fibres’ (Edman, 2003) with Marieb (2003) imparting each individual muscle can consist of thousands of muscle fibres. The depiction of the muscle which is presented is that of layers which are progressively stripped away.
Figure 1.1 The Organisation of Skeletal Muscle taken from Marieb (2003).
Each muscle fibre is composed of tightly packed sub units of ‘myofibrils’ which account for most of the volume of the fibre and are approximately 1 µm wide and run the entire length of the fibre (Hunter, 2000). The sarcolemma surrounds each muscle fibre and is the cell membrane which encases the sarcoplasm (Martini, 2006). The sarcolemma has a characteristic transmembrane potential due to the unequal distribution of positive and negative charges across the membrane, a sudden change in this transmembrane potential is the first step that leads to a contraction (Tortora and Grabowski, 2003). Encasing the myofibrils are the T tubules (figure 1.2) which act as the transductive highway for electrical neuromuscular situation which is termed the action potentials which triggers the muscle innovation (Martini, 2006).
Figure 1.2 The microscopic view of the muscle fibre taken from Marieb (2003)
Once inside the myofibrils it becomes apparent that light (I) and dark (A) bands span the length of the whole myofibril which give the muscle its striped appearance (Marieb, 2003). Detailed examination of the banding reveals that the light I band has a midline interruption, a darker area called the Z disc, and the dark A band has a lighter central area called the H zone (Marieb, 2003) as displayed in figure 1.3.
Figure 1.3 The microscopic view of the myofibrils taken from Marieb (2003).
Myofibrils are actually chains of tiny contractile units called sarcomeres which are aligned sequentially down the length of the muscle; within each sarcomere there are contractile units are termed myofilaments (Edman, 2003). The myofilaments are composed of thick and thin filaments; which are made predominantly of contractile protein molecules, actin and myosin (Hanson and Huxley, 1953) as depicted in figure 1.3. The myosin filaments extends the whole length of the A band, with the midpoint of the myosin being bare and either end consisting of small stud like projections (Edman, 2003). These heads are known as either myosin heads (Edman, 2003) or cross bridges (Tortora and Grabowski, 2003) due to their role of linking the thick and thin filaments during contraction. The actin filament is anchored to the Z disc; when contraction occurs the actin filament slides toward the centre of the sarcomere and the light zone disappears due to the actin and myosin filaments overlapping.
So there you have it a basic guide to the micro and macro structure of human muscle. I feel the areas which are most important to an athlete in an applied context are the excitability and contractility abilities of a muscle. Simply because when we are conducting resistance training these are the areas which we are working to enhance!
Written By Nicholas Jones DNA Sports Performance Director
Welcome to this post on human skeletal muscle. Let’s get straight on with it then! Muscle is composed of several different fibre types that have been categorised with the use of numerous techniques however most athletes will hear the term "fast and slow twitch" at some point in their careers. But what does it all mean?
Peter et al. (1972) identified muscle fibres as slow oxidative (SO), fast oxidative glycolytic (FOG) and fast glycolytic (FG) based upon the histochemical methods using both mitochondrial enzyme and myosin adenosine triphosphatase (ATPase) activities to differentiate fibres. A second classification system, also based upon histochemical methods, was employed by Brooke and Kaiser (1970); it is based solely upon ATPase activities of different fibres. This method identifies one slow-twitch fibre (type I) and two fast-twitch fibres (type IIA and IIB). More recently however Schianno et al., (1989) has used immunochemical analysis, revelling myosin heavy chain isoforms (MHC) I, IIa and IIb, in the analysis of a single muscle fibre. An additional MHC IId has been electrophoretically identified by Termin et al., (1989). However, fibres containing this isoform have been histochemically characterised and designated type IID, and also appears to be synonymous with type IIX fibres characterised immunochemically; histochemically it is referred to as type IID / X (LaFramboise et al., 1990).
Lots of people think that force generation capacity may differ between fast and slow fibres, however this is not technically the case. ATP is split faster and therefore the force generated over time is greater for fast than slow twitch fibres, due to the reduced time for cross bridge cycling (He et al. 2000). Billeter & Hoppeler (2003) argue that the transfer of this data to whole muscle has proved difficult, with correlations between fibre composition and muscular performance proving illusive; however they do convey the main factor in determining muscle strength is muscle volume.
Interestingly for strength and conditioning coaches and their athletes is the evidence that fibre type changes can occur from strength training (+17.08% Type I & +15.89% Type IIa; -49.69% Type IIx) (Willoughby & Pelsue, 2000) and Martel et al., (2005) (+ Type I; -Type IIx). This change in fibre type can help contribute in enhancing sporting performance if the correct change is evoked through effective programming.
So there you have it a basic guide to the muscle fiber types. So next time someone says "you must be made of fast twitch fibres" you can reply "which type of myosin heavy chain isoforms are you referring to? I work with DNA Sports Performance to enhance my percentage contribution of fibre types which lend themselves to enhancing my sporting performance."
Written By Nicholas Jones DNA Sports Performance Director
