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
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 . 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 . 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
. 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,
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
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
Desbrow B, Biddulph C, Devlin B et al. The effects of different doses of caffeine
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
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
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.
Effect of training volume on strength
Much debate rages within the strength and conditioning
community as to the optimal number of sets to perform for a
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.
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
Robbins DW, Marshall PWM, McEwen M. The effect of training volume on
lower-body strength. J Strength Cond Res, 2012, 26, 34–39.
Strength and Conditioning
London Sport Institute
Middlesex University, UK
Email: [email protected]
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