• 18 APR 14
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    Critical assessment

    Critical assessment

    I have highlighted the advantages and benefits of lactate threshold profiling for directing a structured training programme throughout this website. However, I haven’t had much time to emphasise the value of conducting regular Critical Power tests to support peak power output and interval training sessions.

    As most cyclists will only have a restricted expendable training timetable, focusing on all energy systems (ATP for sprinting and neuromuscular work/ Anaerobic Glycolysis for slightly longer intense efforts such as attacks and hill climbs/ Aerobic glycolysis for threshold and full capacity work/ Aerobic fat metabolism below threshold) is particularly challenging. Although this is important to become an all-round good cyclist.

    Focusing purely on threshold power will detract from developing 30 second to 10 minute average powers which can be as important as threshold power under race conditions, to chase groups, bridge gaps, accelerate out of corners and sprint without fatiguing considerably. However, high intensity interval training (HIIT) published by Tabata and protocols investigated (articles cited below) by Gibala, Ronnerstad and Burgomaster have shown to positively affect endurance capacity, VO2 max and lactate threshold power. I will be posting a more detailed review about how high intensity training combined with strength conditioning can limit and sometimes reverse the effects of sarcopoenia (muscle atrophy) in aging athletes. The loss of the anaerobic capacity in veteran cyclists is more commonly being cited as the predominant issue in reduced cycling performance. Whereas VO2max and maximal heart rate declines with age, cycling efficiency may actually improve. I thought the article here is a good, rare piece of sports journalism on the subject.

    Therefore, measuring a cyclists change in Anaerobic Work Capacity or AWC (the amount of energy in joules available above threshold power) helps a coach or physiologist understand if the higher intensity energy systems have been neglected too much during training. In contrast, cyclists with strong peak powers, such as sprinters or track cyclists may purposefully wish to sacrifice a high AWC in favour of elevating their lactate threshold. In essence they are converting lots of their fast (glycolytic) twitch fibers to more aerobic types (slow oxidative) which are less fatiguable, to gain an optimal balance of both.

    Whichever the objective,  increased/ decreased or maintained AWC, measuring this parameter is the best way to track these changes under controlled conditions. The Critical Power assessment also gives an indirect estimate of the absolute functional threshold value (as opposed to the physiological lactate threshold, difference being that the critical power threshold value is hypothetical).

    To demonstrate its usefulness it is worth looking at the changes seen between two CP tests I have recently conducted on a client training for Le Mans 24hr event in August this year.

    The aim of his training has been to maintain his AWC and particularly 3-10 min average powers, while looking to improve his lactate threshold by at least 10% (29Watts). The first CP test conducted in January can be seen in the far right column table below, an apparent CP value of 290W was recorded which was confirmed by a lactate profile of 292Watts. This AWC value was used to design very specific interval sessions, relying on a pyramid format for power intensities ranging from  2 min anaerobic to 10 minute threshold durations performed twice per week as a supplement to the main training objectives at the weekend for sub-threshold distance and endurance.

    Following a three month structured microcycle periodisation of Strength (resistance work in the gym) and Endurance work, I conducted the follow-up CP assessment. From both the table and graph we can see a consistent improvement for all four time limited trials.

    CP_Table_Example

    The results show a consistent increase for each of the short duration trials (1-3 min) of about 20Watts, which may include error from between occasion variability, however these are all positive deviations, suggesting a significant training effect. But what is more interesting is the larger difference (34w) for the 10 minute trial which is less prone to random variation. These changes from baseline result in an increased Critical Power value by 30Watts, yet the AWC has decreased slightly (758 Joules) due to the slope of the curve (both represented with high regression coefficients; 0.997 and 0.993), suggesting less energy above the threshold is at the athletes disposal, but mainly because his threshold is somewhat higher. If the AWC value had been drastically different, and depending on the objective, interval sessions based on this number would be revised as to target the relevant energy system and duration, ie power over time.

    CP_Graph_Example

    So the conclusions taken from these data sets, to revise the training plan accordingly would be to make sure that the longer two minute anaerobic system is as solid as can be with a large amount of exposure to these intensities on the turbo or outside with short hill reps or ‘sprintervals’. Then the cyclist can enter the next crucial aerobic endurance phase focusing on the total aerobic capacity with sessions targeting various durations of VO2max and short upper threshold intensities (3-10 minutes) which will prop up that threshold power value even more while getting some quality, very long tempo/ upper endurance training rides in, before progressing to much harder/faster training rides and Time Trials next month. This should ultimately  maximise the proportion of the aerobic capacity at the athletes disposal, peaking at the right time, and free them up enough to focus on distance strategies, pacing, nutrition, recovery and psychology….as striving for peak performance is a challenge in itself!

    Refs.

    Optimizing interval training at power output associated with peak oxygen uptake in well-trained cyclists. Rønnestad BR, Hansen J. J Strength Cond Res. 2013 Aug 12.

    Short intervals induce superior training adaptations compared with long intervals in cyclists – An effort-matched approach. Rønnestad BR1, Hansen J, Vegge G, Tønnessen E, Slettaløkken G.Scand J Med Sci Sports. 2014 Jan 1. doi: 10.1111/sms.12165. [Epub ahead of print]

    Physiological and performance adaptations to high-intensity interval training. Gibala MJ1, Jones AM.Nestle Nutr Inst Workshop Ser. 2013;76:51-60. doi: 10.1159/000350256. Epub 2013 Jul 25.

    Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. J Physiol. 2008 Jan 1;586(1):151-60. Epub 2007 Nov 8. Burgomaster KA1, Howarth KRPhillips SMRakobowchuk MMacdonald MJMcGee SLGibala MJ.

    Tabata I., Nischimura K., Kouzaki M., Hirai Y., Ogita F., Miyachi M., Yamamoto K. (1996)Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2 max. Medicine & Science in Sports & Exercise 28(10), 1327-1330. [PubMed]

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