About Physiology

About Physiology

Physiology is the study of how living organisms function. This includes processes such as respiration, muscle contraction and reproduction.


Exercise physiology focuses on how the body moves and its adaption to the stress of exercise. Most of us recognize the benefits of exercise and the potential improvements to our general health and well being. However, the key issue is to use the knowledge of exercise physiology to understand how to best achieve our exercise objectives.

Many of the commonly held beliefs relating to exercise some are poorly substantiated and others are completely fictional. A classic example is the old adage “no pain no gain” which unnecessarily associates exercise with discomfort and can result in injury and over training.

In this module relating to rowing, physiology includes the muscles involved in the rowing action as well as energy systems (aerobic and anaerobic) the muscles use to perform the rowing action.






Aerobic vs Anaerobic Exercise


In this module, we have separated exercise into two distinct groups;


1) Aerobic Based

2) Anaerobic Based


When we exercise, the body generates energy (by burning fuels) to perform work. The principal fuels used are the body’s stores of fat, carbohydrate or protein. These fuels can be converted into energy by one of two processes, the aerobic metabolic process or the anaerobic metabolic process.


At the beginning of exercise, energy is initially produced anaerobically until the respiratory and cardiovascular systems respond and supply the oxygen necessary for aerobic energy production, hence the increase in breathing and heart rates. Once oxygen supply is sufficient, most of the energy will be produced aerobically, with the balance supplemented anaerobically. The lactate formed by this residual anaerobic production is easily dissipated by the body’s organs, avoiding any onset of fatigue.


As exercise intensity increases, the ability of the muscles to produce energy aerobically will reach a limit (defined by the capacity of the respiratory and cardiovascular systems to supply additional oxygen). At this point the body cannot supply enough oxygen, and energy production moves to the anaerobic system. This transition point is the maximal aerobic output and is called the aerobic (lactate) threshold. Exercise above this level causes a rapid build-up of lactate, leading to muscle fatigue which will cause cessation of exercise.


Knowledge of the aerobic/anaerobic process is essential for the successful attainment of specific exercise aims. Fat burn (weight maintenance), cardio-vascular training (cardio-vascular or endurance fitness) and anaerobic training (tolerance to fatigue) all rely on an understanding of the way our body produces energy.





Aerobic Based Exercise


The aerobic process consumes fuel in the presence of oxygen (supplied by the flow of blood) producing by-products, carbon dioxide and water, which are expelled by respiration and perspiration. The aerobic process provides the majority of the energy used by the slow acting muscle fibers (crucial to endurance activities).


At lower intensities the body uses a mixture of fat and carbohydrate as its source of fuel. If the exercise objective is weight loss, it is necessary to burn as much fat (as opposed to carbohydrate) as the source of fuel as possible. This is best achieved at lower intensities and over longer durations. As soon as the intensity is increased the aerobic process starts to burn more carbohydrate and the fat loss effect will be reduced. A low intensity (60 - 70% of the maximal aerobic output) is typically that at which you can hold a conversation: it is by no means strenuous and is about that achieved by a brisk walk.

If the exercise objective is aerobic (cardio-vascular/endurance) training then it is necessary to exercise at an intensity which will avoid fatigue due to lactate build up. This is best achieved at moderate levels of intensity over medium/long durations.


At about 70 - 80% of the maximal aerobic output, lactate begins to accumulate in the blood supply at a greater rate than it can be extracted by the liver, kidneys and other organs. Exercising above this intensity will cause progressive accumulation of lactate in the blood, increased heart and breathing rates, muscle fatigue and, eventually, the cessation of exercise. Prolonged exercise at or below this intensity will maintain lactate at non-fatiguing levels and exercise duration will be limited solely by the depletion of available fuel stores.


A sustained exercise program of aerobic conditioning will improve the efficiency with which the respiratory and cardiovascular system can supply oxygen. This improves lung function, heart function, vascular efficiency and capillary growth, leading to improved well being and endurance.





Anaerobic Based Exercise


The anaerobic process occurs when there is not enough oxygen in the blood to produce energy aerobically. This process consumes carbohydrate as its primary source of fuel and produces a by-product called lactate. It is lactate which produces the muscle soreness and fatigue associated with excessive exercise. The anaerobic process provides the majority of the energy used by the fast-acting muscle fibers (crucial to strength and power activities).


Training at anaerobic intensities (85 - 100% of maximal aerobic output) can condition the body's tolerance of lactate, although the benefit may be more psychological than physiological. It can also increase the aerobic threshold. The level of exercise intensity at which lactate begins to accumulate (lactate threshold) can be altered by improving the efficiency of the aerobic process i.e. by training at moderate levels of intensity.

Prolonged exercise at high intensity not only reduces the weight reduction and aerobic training effects, but the rapid onset of fatigue can cause poor technique which may increase the risk of injury.


A form of anaerobic training is resistance/strength based training.






Resistance Training


Resistance training is designed to improve either muscle strength or size. The muscle cells are purposely damaged through a process of overloading. The body reacts instinctively to repair the damaged cells so they can cope with any future overload, increasing their size and strength in the process.

The muscles themselves do not actually increase in number, as some might think: the human body has a genetically defined number of muscle cells.

Muscular fitness is a combination of strength, endurance and flexibility. Resistance training occurs over a short time frame and does not necessarily improve endurance capacity or for that matter flexibility. There may even be a decrease in endurance capacity because as the muscle cells grow the fluid between the cells, essential to oxygen transportation, is reduced.

Therefore depending on your exercise objective training needs to be specific.







The Physiology of Rowing


Rowing is a full body exercise, it uses all the major muscles groups of the legs, torso and arms. Elite rowers are recognized to have outstanding aerobic as well as anaerobic capacities. In a 2000 meter race, rowers utilize a unique physiological pattern. At the start of the race rowers begin with a sprint, this places excessive demands on the anaerobic energy source. This is followed by a time period (usually ranging between 4-7 minutes) of high aerobic steady state rowing and then an exhaustive sprint (again anaerobic) at the finish. Rowing is therefore more of a power endurance sport than a strength sport.


However, rowing does require strength, a rower's training program consists of a combination of endurance, power and strength exercises. This is a specific program so rowers can train their body to tolerate and adapt to the excessive energy demands. This specific training program includes a mixture of workouts of variety of intensities throughout the year. These workouts vary according to the time of year, in the winter months rowers will focus on 'conditioning', this is predominantly endurance training (high volumes of training at low intensities) concentrating on rowing technique and will also include strength training. In the spring months, rowers will start to involve high intensity training in preparation for the racing season during summer.


Full Body Fitness



When rowing, the oarsperson is connected to the boat or rowing machine at the balls of the feet (the footboard) and the fingers (the handle). All the muscle groups in-between (legs, torso and arms) contribute to the rowing action.


(Note: the shading on the above diagram represents the relative intensities of muscle loading during the stroke. Red represents higher loading and Blue represents moderate loading.)


The muscles of the legs are a dynamic muscle group, contributing the majority of the range of motion and around 50% of the total work. As the knees pass through 90 degrees they begin to lose their bio-mechanical effectiveness. At this stage the muscles of the torso and arms begin to contribute.


The muscles of the torso are a static muscle group, contributing very little to the range of motion and around 20 - 30% of the total work. The muscles of the torso work predominantly to provide a strong connection through which to transfer the work of the legs and arms. The muscles of the arms are a dynamic muscle group, contributing the balance of the range of motion and around 20 - 30% of the work.


(Note: these muscle proportions will vary greatly between individuals dependant on physiology, sex, age, etc.)

Even amongst other whole bodied aerobic pursuits like swimming and cross country skiing, rowing is unique in that by transmitting the work through the body, it recruits all major muscle groups sequentially and in proportion to their strength. Utilising the muscles in this way provides an even aerobic load over all of them.


So when rowing at 80% intensity, the leg muscles, torso muscles and arm muscles are all loaded to 80% of their individual capacity and they fatigue evenly, optimising the exercise benefit and lessening the risk of overloading any particular muscle group.




Muscles Used When Rowing


Rowing uses a broad range of muscle groups. By utilizing such a large muscle mass, rowing is unequalled in terms of aerobic benefit. The muscles highlighted above are used throughout the rowing action.



Muscle Characteristics of a Rower

Many people think that to row you should have a strong upper back and arms, however this is not the case. Since the invention of the sliding seat, the legs are the primary movers in the rowing stroke.

It is the explosive power of the legs which initially moves the boat and the back and arms add to and follow through from the legs. The arms play a minor role with regards to energy output and are only really important for technique.

Rowing uses a relatively slow cadence stroke (a maximum of 35 - 40 strokes per minute). Rowers generally have an above average percentage of Type I (slow twitch) muscle fibers concentrated mainly in the quadriceps and deltoid muscle groups. Rowers have up to 75% slow twitch muscles compared with 40 to 50% in the general population.

Rowers have large muscle fibers with a high density of mitochondria and capillary in both slow twitch and fast twitch muscle fibers. This assists in meeting the high aerobic demands of rowing.



Ventilation and Breathing


The word 'ventilation' refers to the exchange of gas in the body. Rowers have been known to have some of the highest values of oxygen consumption amongst endurance athletes. Oxygen consumption in highly trained rowers have been observed at up to 240 liters per minute as compared to 100-150 liters per minute for untrained athletes. This is because rowing requires the use of a large number of muscle groups, and on average competitive rowers are large in size relative to most endurance athletes.




During the rowing stroke the respiratory muscles are used to support the back for the production of force as well as for breathing. At the start or ’drive phase’ of the stroke, the position of the body leaning forward with knees up can increase pressure on the abdomen, making it hard to inhale and limiting ventilation. As a result, some research has suggested that rowers should synchronize their breathing with their rowing stroke with a pattern of inhaling during the drive and exhaling before the drive. However, it is more efficient for the exertion of maximum force to exhale during the drive. The body is generally very quick to find the most efficient way of ventilation during exercise, and no forced sequence of breathing is usually needed.







Heart Rate and Rowing


A fairly accurate method of measuring the physiological intensity of exercise is to monitor heart rate. Exercise intensity measured on the WaterRower or whilst rowing on the water in terms of speed or distance is very subjective as it depends on the individual’s physiology, age, weight, sex, physical condition, etc. These measurements can often vary according to an individual’s tiredness, hydration levels, stress, and general well-being.


The most effective method of training is by setting a target training intensity (heart rate zone) as a percentage of your maximum heart rate. Within each zone of training intensities, subtle but different physiological effects take place.



Heart Rate Zones

Training Objective Heart Rate Training Zone Type of Training Program
Aerobic Conditioning 65-75% of Max. Heart Rate Steady State, Platform and Pyramid Training
Fat Burning 55-70% of Max. Heart Rate Steady State Training
Strength Training 80-100% of Max. Heart Rate Interval and Resistance Training
Race Preparation 70-85% of Max. Heart Rate Steady State, Platform, Pyramid Training