Physiology of exercise essay help online

Competitive cross-country skiing is typically considered an endurance event that is physically demanding and requires athletes to compete over a wide range of distances (male: ~1400 m to 50 km, female: ~1000 m to 30 km). The shortest event is the sprint race, typically around 1400 m for men and 1200 m for women. The sprint event begins with an individual time trial over the course to determine the top 30 fastest times, only these top 30 athletes progress to the quarterfinals (and receive world cup points). Approximately 1 and ½ hrs after the individual time trial has been completed the quarter-final heats begin, there are 5 heats with the top two from each heat plus the two fastest losers progressing to the semi-finals, where the top two from each semi plus the two fasted losers progress to the final. Therefore the finalists will have competed in the 3 finals over a time period of ~1 and ¼ hrs and 4 races in just under ~3 hrs.

The sprint skiing event therefore 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 optimized to recover between each race the athlete has. This recovery period is reduced each time the athlete progresses to the next round and maybe as little as 10-15 minutes between the semi-final and final. Finally, as with all other cross-country skiing events, the sprint event can be either raced in the ‘classic’ style or in the ‘free’ style (otherwise known as skating) format, over a course that typically contains several small hills and many tight turns.

Scenario: The race
Imagine you are standing on the start line of the men’s sprint final (skating), the weather is good, there is a clear blue sky and the air temperature is -8 °C, whilst the snow temperature -6 °C. You are nervous, a little fatigued still and trying to keep moving to both keep warm and keep the ski wax from sticking to the snow. Your heart rate has risen to 110 beats per minute (b.min-1) and you are sweating mildly, breathing 18 times per minute and your tidal volume has increased.
The starter is ready, your muscles tense as you brace yourself and adopt your starting position for the start, the starting signal sounds, you leave the line double poling as fast as you can to hopefully gain a good position in the race (somewhere near the front) to make the ascent up the first and most difficult climb. You are in second place going up the climb trying to conserve your energy even though the pace is fast; you know there is some rest period over the crest of the hill to gain some recovery so you work hard over the top of the hill so that your speed on the downhill is good. It has taken ~ 1 min to crest the hill, as you crest the hill your heart rate (196 b.min-1) and minute ventilation (204 L.min-1) are almost at max and breathing is very hard.

Half way down the hill you are travelling at ~ 55 km.h-1 (about 500 m), there is a long 180-degree turn coming up and your aware of the competitors around as you try to maintain your position, your legs have not fully recovered as you step round the bend being careful to try and keep your speed and balance. As you clear the bend you start the second climb and the other racers are vying for position so you move out to block them coming past. Half way up this small but steep hill you decide to make your break; you kick and race as hard you can up the hill. You push hard again over the top of the hill, double poling to maximise your speed for the next downhill section back into the stadium even though your legs are burning and arms are tiring. You realise the importance of maintaining a good position down the hill into the final third of the race. As you glide down the hill you are gasping for air trying to regain control of your breathing, you get into a tuck position to maximize your speed and recovery, your legs are tired and a little unstable from your efforts as well your blood lactate levels being close to max.

You have opened up a gap on your nearest competitor, but you can’t relax as you know they will attempt to catch you in the slip stream you create. Position is crucial if you are going to win the race, you want to be in first place for the final 250 m, as you approach the final small climb you kick again to the top, making sure you have the inside line round the corner. There is only ~ 20 sec left to race, your competitors are trying to catch you before the final straight, the last corner is important, you know you must control the inside line as you want your competitors to take long way round the bend if they want to overtake you. As you come out of the final corner you have the ideal position and you sprint with every ounce of energy you have left, double poling this is your final effort. Your speed in the final 100 m reaches 7.5 m/s; your heart rate and minute ventilation are at max and fatigue is preventing from accelerating any more, you hope that you don’t slow as much as your competitors during the final 50 m. You sense the other competitors around you, every skate and double pole propels you closer to the line, the crowd are cheering every last meter covered, the line approaches and you stretch out your left leg to make sure your timing chip stops the clock with you in the lead.

The finish was close, closer than you would have liked, but you realise you have won, and you collapse to the ground gasping for air. Exhausted and your chest heaving with the effort of trying to breathe and recover from your efforts. You lie there for 30 sec or so to recover and then slowly you get up, and let out a scream of elation raising your hands in the air to celebrate. The race is over and you have won!!!!

Now answer the questions below:

Assessment questions:
(1500 words)

At the start

1. It has been suggested that in cross-country sprint skiing 20 min is enough time to recover between heats. Explain the most likely mechanism responsible for this recovery process to occur? (20 marks)

One minute in

2. What changes in your muscles promote greater oxygen diffusion and therefore greater oxygen uptake? (15 marks)

3. The air temperature during the race is – 8 °C which means that mean skin temperature is likely to fall to ~ 22 °C whilst core temperature increases slightly. What impact is this likely to have on force production and muscular power during the race? (20 marks)

4. What mechanisms are regulating acid base balance during the race? (15 marks)

The finish

5. Muscular fatigue at the end of each heat is severe, particularly in the m.triceps surae and m.vastus lateralis. Explain the likely causes of fatigue during a single sprint? (20 marks)

6. Explain which energy system is likely to dominate during this event and give approximate contributions to performance from both the anaerobic and aerobic systems? (10 marks)

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