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Read the case study below and place yourself in this scenario, consider all the physiological responses that occur throughout the event and how they are inter related. Then answer the questions at the end, they should NOT be one or two word answers.
Background:
Competitive rowing is an endurance event that is physically demanding and requires the rower to sustain an almost maximal effort throughout the duration of the event (~5 -7 min). The 2 000 m row requires significant contribution from both the anaerobic and aerobic energy systems to fully realize optimal performance. Just as importantly, all physiological systems need to be controlled and regulated so that they function in a coordinated way, they will never be in what might be called a ‘steady state’ condition and homeostasis will be disrupted as they continually adapt to new physiological stresses throughout the race.
Scenario: The race
Imagine you are sitting on the boat, on the start line of the men’s/women’s coxless fours varsity final, you are sitting in the stroke position and the wind is strong and the water choppy. You are nervous, the boat is moving around and you are waiting for the rest of the crews to be ready, your heart rate has risen to 110 beats per minute (b.min-1) and you are sweating, breathing 18 times per minute and your tidal volume has increased. The crews are ready, your muscles tense as you brace yourself for the start, the starting signal sounds, you power away from the starting gates, your first 20 strokes are at maximal power, you settle into a rate of 38 strokes per minute (spm). At the end of the first minute your heart rate is at 198 b.min-1, your breathing frequency is 76 breaths per minute (2 breaths per stroke), minute ventilation has increased to 195 L.min-1. Your core temperature has increased by 0.5 degrees and you are now sweating more profusely.
A couple of minutes later you pass the 1 000 m marker, you are working very close to your maximal oxygen uptake (VO2max) now and your stroke rate has settled down to 34 spm. Your heart rate has dropped a little to 190 b.min-1 and in the race, your boat is roughly level with two other boats as the 3 boats lead through the half-way point. At this point you are giving each stroke about 85% of maximum power as you and the other boats prepare and position yourself the last 500 m effort.
With 500 m to go you have pulled out to a small lead, you are a canvas ahead; your legs are burning, your lungs gasping for air and your muscles desperate for oxygen. You are feeling tired, but you draw strength and motivation from the fact you leading and that you are in the last quarter of the race, you summon all of your strength for last push as the crew closest to you have upped their stroke rate again to 38 spm, you follow suit.
Into the last 250 m you are now at 39/40 spm, you are at your limit physically; your heart rate is now 204 b.min-1, both your energy systems are at max squeezing every last drop of energy from your body and your core temperature is now at 38 degrees. Your boat has maintained its lead, but with each stroke the boat closest to you starts to pull closer with every stroke. Into the last 100 m, less than 10 strokes, you are giving everything you have got as all your limbs are burning and fatiguing, it’s going to be a close finish as you try and just maintain your lead.
Across the finish line, two tenths of a second ahead of second place, you have won! You stop rowing – exhausted, you slump back into the person behind you. You gasp for air, still breathing at 70 times per minute, your whole body is aching, and the burning feeling in your legs and arms is starting to ease as your body begins to recover from maximal effort. You now start to sweat profusely as your body tries to cool itself down, the sweat is dripping off you.
Fifteen minutes later after a jubilant row back to the docks your heart rate, ventilation rate and VO2max are almost back to normal. Your core temperature is still high and you have lost 2 kg in body mass and your legs still feel heavy from your excursions, blood lactate remains elevated even after this time period.
Assessment questions:
Part A – 1000 words (60%)
At the start
1. At the start your heart rate, breathing frequency and ventilation have all increased, what is responsible for raising these before you start?
2. What changes have occurred in pH and hydrogen ion (H+) levels during warm up, how might this help performance at the start of the race?
One minute in
1. What changes in your muscles promote greater oxygen diffusion and therefore greater oxygen uptake?
2. Rowing full speed at 38 spm put new demands on your body. What are these new demands and how does your body respond to them?
3. You are breathing at 76 breaths per minute, twice the number of strokes you are taking, why do you adopt this breathing frequency?
Halfway mark
1. Why do your muscles feel like they are burning?
2. Shortly after the end of the first minute you reduced your stroke rate and therefore decreased the physiological demands on your muscles, why have you done this? What are the changes in your condition as a result?
The finish
1. You have stopped rowing and you are at rest, but your heart rate and breathing frequency are still very high, why is this still the case?
2. What changes have occurred to your blood chemistry since the start of the race? Think about glucose levels, pH, lactate levels, temperature etc.
3. What physiological changes have occurred in the last 15 min to allow oxygen uptake to recover to normal?
Part B – 500 words (40%)
1. a). Discuss the principle systems responsible for contributions to energy production during the 2000 m rowing event; explain the contribution made by each energy source to the overall energy demand (indicating the likely percentage contribution from each energy system); b) discuss and explain the likely mechanisms of muscular fatigue during this event.
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