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The importance of muscular strength in athletic performance: Training considerations

Summary article: The importance of muscular strength: Training considerations (Suchomel, Nimphius, Bellon & Stone, 2018)

Introduction

Muscular strength is an important aspect of sports performance (see previous blog post: The importance of muscular strength in athletic performance for summary article). Therefore, strength & conditioning coaches and sport science professionals should understand methods of improving strength and the underlying physiological factors that affect it. This will allow them to effectively prescribe resistance training modalities and progressions in relation to the needs analysis of the sport and individual athlete.

Physiological factors

Muscular strength can be influenced by confounding factors including initial strength levels, training status and genetics. However, several morphological and neural factors underpin strength development that affect overall muscular strength in combination with the above factors. It is important to note the below physiological factors combine to increase strength, rather than any one reason presenting the underlying cause.

Muscle hypertrophy and architecture

Alterations in skeletal muscle hypertrophy can impact a muscle’s ability to produce force and power. This means the greater a muscle’s cross-sectional area, the more potential it has to produce higher levels of force due to greater force-velocity characteristics. Physiologically, an increase in the number of cross-bridge interactions between actin and myosin within existing and newly formed sarcomeres is the reasoning behind this. This can also be linked to greater muscle fibre pennation angles in muscles benefitting from greater hypertrophy, increasing the number of cross-bridge interactions within the muscle due to a greater number of muscle fascicles within a given area. It is important to note, however, muscle size and strength can vary between individuals in response to different training stimuli.

Musculotendinous stiffness

Muscular strength is inherently related to the concept of tissues expressing spring-like behaviour, which influences subsequent muscular performance. Stiffness can be described as the relationship between a given force and the amount of stretch the tissue undergoes, with increased stiffness (i.e. less stretch) leading to an improved ability to transmit force. Therefore, tendon stiffness (along with structures within the muscle such as actin, myosin, titin and connective tissues) is an important part of muscular strength and the transmission of force and related characteristics such as rate of force development (RFD) and power.

Motor unit recruitment

Motor units are recruited in a sequence from smallest to largest, meaning a task that requires low amounts of force and RFD will recruit smaller motor units that include type I (slow twitch) fibres, whilst tasks requiring large amounts of force and RFD will recruit large motor units that include type IIa/IIx (fast twitch) fibres. Therefore, although type I motor units may increase force production, tasks that require a combination of all fibre types (i.e. tasks requiring larger forces and/or levels of RFD) will allow greater strength development.

Rate coding, motor unit synchronisation and neuromuscular inhibition

Following specific motor unit recruitment, the frequency at which action potentials can be discharged to the motor unit’s muscle fibres can modify force production properties. Therefore, the magnitude of force may increase when firing frequency is increased. This can be linked to force-time characteristics with higher force magnitudes and RFD a result of increased firing frequency of motor units. Furthermore, simultaneous activation of more than two motor units (synchronisation) may enhance peak force production due to greater levels of RFD over short time periods. However, motor unit synchronisation may be more related to RFD than magnitude of force production. In contrast, neuromuscular inhibition (reduction in neural drive in response to neural feedback from muscle and joint receptors, leading to a decrease in force production) may negatively affect strength development. However, this could be negated through heavy resistance training through the downregulation of afferent feedback.

Periodisation and programming

It is proposed that residual effects of previous training phases carry-over into future training phases. Therefore, different types of strength training can be linked to complement one another within an annual plan and periodisation strategy. There are many methods of periodisation and programming, so a deep discussion was deemed beyond the scope of the current paper. However, annual planning is the foundation of an athletic development program, covering the outline for training, competition, monitoring, testing and other important delivery aspects. It is then structured, or periodised, into a methodical and logical structure, manipulating training variables throughout the calendar directed at achieving performance goals. In relation to strength development, periodisation has been shown to produce greater benefits than non-periodised programs.

Annual planning usually features phases of preparation, divided into general and specific subsections, competitive, divided into subsections of pre-competitive, competitive and peaking phases, and transition phases. Within the different phases, various physiological adaptations can be targeted to produce desired outcomes at certain timepoints in the contribution to performance goals. Within this, programming elements make up exercise selection, sets and repetitions, rest periods, and load prescription.

As previously discussed, the importance of increasing muscular strength is related to improving force-time characteristics in the context of sporting performance. Therefore, in the context of a long-term plan, periodisation and programming should be focussed towards the improvement of various performance aspects, as well as elements of strength.

Resistance training methods

There are many different training methods used to develop strength-power characteristics. See table 1 for the theoretical potential of resistance training methods to benefit hypertrophy, strength and power.

Bodyweight exercises

  • Basic resistance training exercises – great to introduce movement patterns

  • Accessible – no equipment needed

  • Versatile – many variations can be used

  • Can be used as a tool for progression to more complex or loaded movements

  • Bodyweight or reduced bodyweight exercises may have implications for increasing explosive performance when training low-load, high-velocity

  • Limited ability to overload, preventing significant improvements to maximum strength

Isolated machine-based and multi-joint free-weight exercises

  • Isolation exercises commonly used as a means of targeted tissue capacity development

  • Incorporation of multiple muscle groups in free-weight exercises may provide a superior strength training stimulus due to requiring greater coordination and muscle recruitment demands

  • The use of single joint machine-based exercises may be questionable when developing strength as athletic performance is rarely isolated to one muscle group, lacking transfer of coordinative patterns

  • A continuum from isolation exercises through to free-weight exercise can be useful in certain settings, such as that of rehabilitation, providing appropriate progressions and regressions

Weightlifting movements and derivatives

  • Weightlifting movements (clean and jerk, snatch) and derivatives (omission of a portion of the full weightlifting movements, e.g. high pull) have been shown to produce superior strength-power adaptations compared to traditional resistance training, jump training and kettlebell training

  • May provide more effective means of force absorption of an external resistance

  • Allows for exploitations of both the force and velocity aspects of power, leading to favourable neuromuscular adaptations

Plyometric training

  • Explosive movements utilising the stretch-shortening cycle (SSC) where a concentric muscle action is enhanced by a previous eccentric muscle action

  • Not normally prescribed to enhance muscular strength – the ballistic nature of plyometrics has the benefit of transfer from strength to power production and RFD

  • Difficult to provide an overload stimulus due to heavier loads resulting in greater impact forces and lengthening time of the SSC (but is intensity overload necessary with the nature of plyometrics?)

  • Enhancement of muscular strength would be limited from plyometric training

Eccentric training

  • Benefits performance by producing favourable adaptations in mechanical function (strength, power, RFD and stiffness), morphological adaptations (tendon and muscle fibre cross-sectional area) and neuromuscular adaptations (motor unit recruitment and firing rate) due to potential for greater force applied to the musculotendinous unit than force produced by the muscle

  • Accentuated eccentrics (performing the eccentric phase with a heavier load than the concentric phase) may have positive benefits on performance compared to other resistance training methods

  • Heavy eccentrics can produce favourable hypertrophy and strength adaptations

  • There may be a lack of research on eccentric training within the context of an annual plan

  • Residual effects may be heightened, for example delayed onset muscle soreness (DOMS) may be amplified as a result of eccentric training

Potentiation complexes

  • Potentiation refers to acute performance enhancements based on a muscle’s contractile history, normally with a high-force exercise used prior to a high-power exercise

  • Plyometric exercises such as depth jumps are thought to be the best method of potentiation for strength performance

  • Potentiation complexes are usually used to enhance muscular power rather than strength

  • There is a lack of research investigating potentiation complexes and improvements in muscular strength, whilst results published provide conflicting results regarding the best methodologies to enhance strength performance

Unilateral versus bilateral training

  • Unilateral exercises are thought to have good transference to sporting performance due to the unilateral nature of various sporting tasks (sprinting, cutting etc.)

  • Strong relationships exist between bilateral resistance training and sporting performance

  • Unilateral training provides higher muscle activation than bilateral training, however stability may be decreased during unilateral training, whilst bilateral exercises can provide a greater overall mechanical platform from which to develop strength

  • The majority of research employs bilateral training methods

Variable resistance training

  • Athletes may be restricted during traditional resistance training exercises because of mechanical disadvantages (e.g. an athlete may be limited during the back squat at specific hip and knee angles)

  • The use of chains or bands can aid relevant sections of a lift based on the mechanical advantage or disadvantage, maximising expressed muscle force throughout the full range of motion

  • Greater adaptations may still be seen at the end range of motion where increased resistance occurs

Kettlebell training

  • Kettlebell training may improve specific measures of strength

  • Training with kettlebells is limited in the capacity to provide an overload stimulus due to technical limitations and aspects such as grip strength due to the size of the kettlebell

  • Further research is needed to investigate the efficacy of kettlebell training on strength levels, although kettlebell training may provide benefits to muscular power due to the explosive nature of the movements

Ballistic training methods

  • Ballistic training features acceleration throughout the entire range of the concentric portion of the lift

  • Provides greater force, velocity, power outputs and muscle activation compared to the same exercises performed quickly, rather than ballistically

  • Promotes neural adaptations to recruit a greater number of motor units, leading to greater force production, RFD and power development

  • Beneficial for explosive strength

  • Ballistic exercises are underpinned by maximal strength, so it may be prudent to first enhance strength in order to enhance the benefits associated with ballistic training

Table 1: Theoretical potential of resistance training methods to benefit hypertrophy, strength and power

Resistance training methods ranked on a scale from +, meaning low potential, to + + + + +, meaning high potential. Assigned exercises, volume-load prescription, and an athlete’s relative strength will also influence adaptations.

Loading strategies

Training to failure

Training to failure can be defined as the point where the barbell stops moving, the sticking point lasts longer than one second, or the full range of motion repetitions can no longer be completed. However, training to failure has been examined with meta-analyses with the outcome suggested to be counterproductive to gains in strength due to the possibility of overtraining and potential exposure to injury.

Combined heavy and light loading