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Performance
Research review
review by Sean Maloney
athletes, the ability to train to shift fibre type would be of Welcome to Research Review, your monthly round- significant benefit. Research has reached a general consensus up of what’s hot in sport and exercise science confirming the potential for conversion between type IIa and type IIx muscle fibres; however, the possibility of conversion between type I and type II fibres is less clear. Wilson et al.
We’re hitting both ends of the spectrum this time, sought to combine data from current research and determine so power athletes and endurance athletes take the extent to which exercise can affect fibre type composition.
note. This issue will feature research investigating Whilst a body of evidence discounts the potential for type concepts such the training effect of incline I/type II interconversion, the results of several studies imply plyometrics, minimalist footwear on running that this may be possible with specific and concentrated economy and optimising dosing for caffeine programming. Perhaps unsurprisingly, a shift towards type II fibres may be facilitated by the performance of power exercises. This conversion may also be facilitated by the Remember: Train hard, train SMART!
thyroid hormone triiodothyronine (commonly known as T3). A transition towards type I fibres may be facilitated by high- volume, long-duration endurance training.
Incline plyometrics may improve explosive
THE SCIENCE
plantar flexion
Muscle fibre type can be classified in three different In our last issue we mentioned a study by Kannas et al. which ways: myosin ATPase staining, myosin heavy chain investigated the biomechanics of performing plyometric drills identification, and biochemically [1–3].
on an incline surface. Subsequent findings by the same Greek research team are soon to be published in the European Advances in myosin ATPase staining techniques now Journal of Applied Physiology and appear to confirm their mean that seven separate fibre types can be hypothesis that these drills can be more effective for identified [1]. In order, from slowest to fastest, these developing explosive plantar flexion.
are: I, IC, IIC, IIAC, IIA, IIAB, and IIB. Twenty male subjects were split into two training groups, Three myosin heavy chain forms were originally half performing plyometrics on an incline surface (15°) and the identified: MHCI, MHCIIa and MHCIIx (previously other half on a flat surface. The training programme consisted known as MHCIIb), and these correspond to the of a series of stiff-legged jumps (8–10 sets of 10 maximal original I, IIa and IIb types identified by staining [2]. It jumps) on the designated surface. Subjects completed four appears that type IC, IIC and IIAC coexpress MHCI sessions per week for a period of 4 weeks. The incline group and MHCIIa genes to varying degrees, and type IIAB showed significant improvements in fast depth jump performance (17% from a 20cm drop, 14% from a drop of Biochemically, fibres are typed as slow-oxidative (SO), 40cm), with activity of the gastrocnemius during the propulsion fast-oxidative-glycolytic (FOG) or fast-glycolytic (FG) phase also increased during these jumps. Improvements in [3]. Type I fibres correlate well with SO fibres; squat, countermovement and slow depth jump performances however, variability in the predominance of energy were not significant. Fast depth jumps were classified by <50° systems means that type IIA and type IIB fibres of knee flexion on impact and slow depth jumps by >60° of cannot be used interchangeably with FOG and FG.
■ Outcome: incline plyometrics appear a viable training Scott W, Stevens J, Binder-Macleod SA. Human skeletalmuscle fiber type classifications. Phys Ther, 2001, 81, 1810– modality for improving explosive plantar flexion and Staron RS. Human skeletal muscle fiber types: delineation,development, and distribution. Can J Appl Physiol, 1997, 22, Reference
Pette D, Peuker H, Staron RS. The impact of biochemical Kannas TM, Kellis E, Amiridis IG. Incline plyometrics-induced improvement of methods for single muscle fibre analysis. Acta Physiol Scand, jumping performance. Eur J App Phys, 2012, 112, 2353–2361.
■ Outcome: the potential for type I/type II interconversion as a Fibre type shifting – what’s actually possible?
consequence of training is still largely unclear: longitudinal studies over several years or more appear necessary.
Type II fibres (categorised as either type IIa or type IIx) are designed for high-force and high-velocity function. These types Reference
of fibres are particularly prevalent in strength and power Wilson JM, Loenneke JP, Jo E et al. A brief review: the effects of endurance, athletes. Conversely, type I fibres are built to function for long strength, and power training on muscle fiber type shifting. J Strength Cond durations – and predominate in endurance athletes. For Res, 19 September 2011 [epub ahead of print].
Research review Performance
Minimalist footwear improves running
Optimising caffeine dosage
The ergogenic potential of caffeine to endurance performance has Part of the appeal of minimalist – or barefoot – running is the been pretty well established. Previous studies have directed potential for greater energy return from the foot and ankle current recommendations for caffeine supplementation, which complex. In theory, this should improve running economy.
currently fall within a range of 3–6mg/kg. The ability to further Previous studies have investigated the effect of footwear on optimise this dose would be of real interest to endurance athletes.
running economy, although did not control for factors such as shoe A team of Australian researchers have attempted to determine at mass, stride frequency and running style (forefoot versus rearfoot which end of the recommendation spectrum this optimal dose lies.
striking). Researchers at Harvard University aimed to address these Sixteen well-trained cyclists performed three separate time trials following the ingestion of a placebo, 3mg/kg, or 6mg/kg of The study measured the biomechanics and running economy of caffeine. These were taken in the form of capsules, 90 minutes 15 habitually ‘minimalist’ runners in four separate trials: a) standard prior to performance. The time trial was designated by a set trainers, forefoot striking; b) standard trainers, rearfoot striking; c) amount of work equivalent to 75% of the individual’s peak minimalist trainers, forefoot striking; d) minimalist trainers, rearfoot sustainable power output for 60 minutes, and lasted for a similar striking. Minimalist trainers were 2.4% more economical when duration. Time trial performance was improved in both caffeine forefoot striking and 3.3% more economical when rearfoot striking.
trials, by 4.2% in the 3mg/kg condition and 2.9% in the 6mg/kg Achilles tendon strain and knee flexion were also reduced in condition. Differences in the two caffeine trials were not minimalist footwear. It was deemed likely that these significant. Heart rate was elevated following caffeine ingestion improvements are a consequence of greater elastic energy return although perceived exertion was not affected.
from the lower extremity. Forefoot striking was not more ■ Outcome: trained endurance cyclists may benefit from the ingestion of caffeine at a dose of 3mg/kg. Doubling the dose ■ Outcome: minimalist footwear may confer small to 6mg/kg confers no additional performance benefit.
improvements in running economy that are independent of running Reference
Desbrow B, Biddulph C, Devlin B et al. The effects of different doses of caffeine Reference
on endurance cycling time trial performance. J Sport Sci, 2012, 30, 115–120.
Perl DP, Daoud AI, Lieberman DE. Effects of footwear and strike type on running economy. Med Sci Sports Exerc, 3 January 2012 [epub ahead of print].
Minimal effect of ionised and non-ionised
compression garments
Resisted movement training – does it work?
Whilst the use of compression garments in sport and exercise is The utilisation of training tools such as sleds and bungees has widespread, research supporting their ergogenic potential is split.
increased over the past few years. These tools allow an adjustable Recent advances in clothing technology have seen manufacturers resistance to be applied to dynamic, sport-specific movement incorporating negatively charged ions into the fabric, which it is patterns. The rationale is that resisted movement training provides hypothesised may improve blood flow. No studies had previously a greater carryover to athletic performance. Hrysomallis has investigated the effects of wearing ionised compression clothing.
conducted a review of the literature to date, to evaluate its Ten trained triathletes or cyclists performed three sprint trials and three endurance trials wearing standard running tights, non- Weighted jump squats at a variety of loads (30%–80%1RM) ionised compression tights and ionised compression tights.
have elicited improvements in jump performance although have Garment type was found to have no effect on peak power, mean not proven superior to plyometric training. Jump training performed power and fatigue during the sprint trials. Similarly, there was no with elastic resistance does not appear beneficial to performance.
effect of garment type on time trial performance, mean VO and Resisted sprint training has been demonstrated to improve sprint heart rate responses during the endurance trials. Interestingly, performance although seems no more effective than regular sprint blood lactate was lower in the non-ionised compression condition training. Limited research suggests that sled-resisted training may during these endurance trials. Given that the ionised and non- be more effective in training the initial acceleration phase; ionised tights produced almost identical compressive forces, the however, further research is necessary to determine its mechanism for this reduction is unclear. ■ Outcome: the study does not support the notion that ■ Outcome: on the whole, resisted movement training does not compression garments improve aerobic or anaerobic appear superior to other training modalities for improving jump Reference
Reference
Burden RJ, Glaister M. The effects of ionised and non-ionised compression garments on sprint and endurance cycling. J Strength Cond Res, 23 November Hrysomallis C. The effectiveness of resisted movement training on sprinting and jumping performance. J Strength Cond Res, 2012, 26, 299–306.
See page 9 for more on compression garments.
Performance
Effect of training volume on strength
review Much debate rages within the strength and conditioning community as to the optimal number of sets to perform for a ch given exercise or muscle group. Whilst the literature has compared single-set to multiple-set training, these multiple-set protocols have only investigated the performance of three to four sets.
Resistance trained populations will commonly perform a volume of work far in excess of four sets per muscle group.
Resear Robbins et al. investigated the effects of high-volume (eight-set) strength training on subsequent strength performance and in comparison to one-set and four-set training.
Thirty-two strength-trained men were randomly assigned to either a one-set, four-set or eight-set training regimen. Training sessions were completed twice per week and consisted primarily of the back squat exercise. Subjects performed repetitions at 80%1RM, which was re-tested after 3 weeks of training, until volitional fatigue and for the given number of sets. Both the four-set and eight-set conditions improved 1RM squat performance after 3 weeks of training; and all three training conditions had improved squat performances following the full 6-week training programme. Improvements achieved by the eight-set group were greater than those achieved by the one-set group. Improvements of the four-set group were not ■ Outcome: it appears that higher-volume protocols are more effective for lower-body strength development in trained Reference
Robbins DW, Marshall PWM, McEwen M. The effect of training volume on lower-body strength. J Strength Cond Res, 2012, 26, 34–39.
Sean Maloney
Strength and Conditioning
Coach/Lecturer
London Sport Institute
Middlesex University, UK
Email: [email protected]

Source: http://www.performancesportandfitness.co.uk/downloads/research-review-volume2.pdf