Stuart C. Miller

Reliability, factorial validity, and interrelationships of five commonly used change of direction speed tests

Change of direction speed (CODS) is often considered a main determinant of successful performance in many team sports and is routinely measured using field‐based tests. However, controversy regarding test selection still exists based upon the reliability and specificity of the tests. The purpose of this study was to determine and compare the reliability, factorial validity, and interrelationships of five frequently used CODS tests (Illinois, L‐Run, Pro‐Agility, T‐test, and 505). Forty‐four physical education students (male n = 24; female n = 20; age; 16.7 ± 0.6), who compete within team sports, to varying levels of competition, participated in this study. Three trials for each of the five tests were recorded. All tests had high (intraclass correlation coefficient) test–retest reliability (r = 0.88–0.95) and low typical percentage error (1.95–2.40%). The principle component factor analysis resulted in the extraction of one significant component which explained 89.52% of the total variance. All selected tests were positively and strongly correlated (r = 0.84–0.89). Based upon the results of this study, it was concluded that all tests are highly reliable and valid measures of CODS, with all tests assessing a general athletic ability to change direction. Future research should investigate the factorial validity of the CODS test within homogenous samples.

Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans

The neuromuscular adaptations in response to muscle stretch training have not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity, and spinal motoneuron excitability were examined during standardized plantar flexor stretches after 3 wk of twice daily stretch training (4 × 30 s). No changes were observed in a nonexercising control group (n = 9), however stretch training elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM (n = 12). Only a trend toward a decrease in passive plantar flexor moment during stretch (-9.9%; P = 0.15) was observed, and no changes in electromyographic amplitudes during ROM or at end ROM were detected. Decreases in H(max):M(max) (tibial nerve stimulation) were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed. Muscle and fascicle strain increased (12 vs. 23%) along with a decrease in muscle stiffness (-18%) during stretch to a constant target joint angle. Muscle length at end ROM increased (13%) without a change in fascicle length, fascicle rotation, tendon elongation, or tendon stiffness following training. A lack of change in maximum voluntary contraction moment and rate of force development at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance) and both muscle and fascicle elongation rather than changes in volitional muscle activation or motoneuron pool excitability.

The Usefulness and Reliability of Fitness Testing Protocols for Ice Hockey Players: A Literature Review

Abstract Nightingale, SC, Miller, S, and Turner, A. The usefulness and reliability of fitness testing protocols for ice hockey players: A literature review. J Strength Cond Res 27(6): 1742–1748, 2013—Ice hockey, like most sports, uses fitness testing to assess athletes. This study reviews the current commonly used fitness testing protocols for ice hockey players, discussing their predictive values and reliability. It also discusses a range of less commonly used measures and limitations in current testing protocols. The article concludes with a proposed testing program suitable for ice hockey players.

Strength and conditioning for fencing

SUMMARY SCIENTIFIC RESEARCH INTO FENCING IS SPARSE AND LITTLE RELATES TO STRENGTH AND CONDITIONING. IN OUR EXPERIENCE OF WORKING WITHIN FENCING, IT IS A PREDOMINATELY ANAEROBIC SPORT CHARACTERISED BY EXPLOSIVE HIGH-POWER MOVEMENTS. CONSEQUENTLY, FENCERS SHOULD BE CAUTIOUS OF SOME OF THE TRADITIONAL TRAINING METHODS CURRENTLY USED SUCH AS LONG SLOW DISTANCE RUNNING BECAUSE THIS IS LIKELY TO BE COUNTERPRODUCTIVE TO PERFORMANCE. INSTEAD, EXERCISES AND CONDITIONING DRILLS THAT DEVELOP REPEAT LUNGE ABILITY, STRENGTH, AND POWER SHOULD BE USED. THE HIGH PROPORTION OF LUNGING ALSO DICTATES THE NEED FOR ECCENTRIC STRENGTH AND CONTROL AND THE ABILITY TO REDUCE MUSCLE DAMAGE.

Increasing the Impact Force of the Rear Hand Punch

ONE OF THE MOST RENOWNED STRIKES WITHIN COMBAT SPORTS IS THE REAR HAND PUNCH. ITS IMPACT FORCE IS SUBJECT TO 5 TRAINABLE VARIABLES: (A) INCREASE REAR LEG DRIVE, (B) FOLLOWING THE STEP FORWARD, LAND WITH A RIGID LEG TO INCREASE BREAKING AND TRANSMISSION OF FORCES, (C) INCREASE THE STRETCH-SHORTENING CYCLE ACTION OF THE TRUNK MUSCULATURE, (D) INCREASE THE VELOCITY OF THE PUNCH, AND (E) INCREASE THE EFFECTIVE MASS. IT IS POSSIBLE, THROUGH APPROPRIATE STRENGTH AND CONDITIONING PROGRAMMING, TO TARGET THE DEVELOPMENT OF EACH.

Plantarflexor stretch training increases reciprocal inhibition measured during voluntary dorsiflexion

Agonist-mediated reciprocal inhibition (RI) in distal skeletal muscles is an important neurophysiological phenomenon leading to improved movement coordination and efficiency. It has been shown to be reduced in aged and clinical populations, so the development of interventions augmenting RI is an important research goal. We examined the efficacy of using chronic passive muscle stretching to augment RI. The influence of 3 wk of plantarflexor stretching (4 × 30 s, two times/day) on RI of soleus and gastrocnemius initiated by tonic, voluntary dorsiflexion contractions [20% of maximum voluntary contraction (MVC)] was examined in 11 healthy men who performed stretch training and in nine nontraining controls. Hoffmanns reflexes (H-reflexes) were elicited by tibial nerve stimulation during both weak isometric (2% MVC) plantarflexions and dorsiflexion contractions at 20% MVC. Changes were examined at three joint angles, normalized to each subjects range of motion (ROM; plantarflexed = 10 ± 0°, neutral = -3.3 ± 2.9°, dorsiflexed = -16.5 ± 5.6°). No changes were detected in controls. A 20% increase in ROM in the stretch subjects was associated with a significant decrease in maximum H-reflex (H(max)): maximum evoked potential (M(max)), measured during 2% plantarflexion at the plantarflexed and neutral angles in soleus and at the plantarflexed angle in gastrocnemius (P < 0.05-0.01). By contrast, decreases in H(max):M(max) during 20% dorsiflexion contract were also seen at each angle in soleus and at the dorsiflexed angle in gastrocnemius. However, a greater decrease in H(max):M(max) measured during voluntary dorsiflexion rather than during plantarflexion, which indicates a specific change in RI, was detected only at the dorsiflexed angle (-30.7 ± 9.4% and -35.8 ± 6.8% for soleus and gastrocnemius, respectively). These results demonstrate the efficacy of soleus-gastrocnemius stretch training in increasing agonist-mediated RI from tibialis anterior onto soleus-gastrocnemius in young, healthy individuals at dorsiflexed, but not plantarflexed, joint angles.

The effects of postactivation potentiation on golf club head speed.

Abstract Read, PJ, Miller, SC, and Turner, AN. The effects of postactivation potentiation on golf club head speed. J Strength Cond Res 27(6): 1579–1582, 2013—In golf, an increase in club head speed (CHS) has been shown to increase driving distance and is correlated with handicap. The purpose of this study was to investigate the effect of a postactivation potentiation (PAP) intervention on CHS. A FlightScope launch monitor was used to record CHS in 16 golfers (aged 20.1 ± 3.24 years, handicap 5.8 ± 2.26) during 2 testing sessions that were separated by 1 hour, using a counterbalanced design. The mean CHS of 3 swings was recorded with (experimental) and without (control) 3 preceding countermovement jumps (CMJs). An increase in CHS of 2.25 mph (effect size, 0.16; p < 0.05) 1 minute after the CMJ intervention was recorded. Therefore, acute enhancements in CHS are possible when performing a CMJ before a golf drive. This may have implications for training and on-course performance enhancement as a result of increased driving distance and possible reductions in handicap; this PAP intervention is practically viable.

Tibialis Anterior Moment Arm: Effects of Measurement Errors and Assumptions

UNLABELLED Accurate estimates of tibialis anterior (TA) muscle force are important in many contexts. Two approaches commonly used to estimate moment arms are the tendon excursion (TE) and geometric (GEO) methods. Previous studies report poor agreement between the two approaches. PURPOSE The purposes of this study were to 1) assess the effect of methodological variations in the two methods of moment arm estimation and 2) determine how these variations affect agreement between the methods. METHODS TA moment arms were determined using TE and GEO. Errors associated with tendon stretch/hysteresis, talus rotation relative to the foot, and the location of the line of action were investigated. RESULTS For TE, large errors in moment arm estimates across the range of motion were found when tendon length changes (P = 0.001) were not corrected for. For GEO, the estimated moment arm was reduced at an ankle angle of -15° when discrepancies between talus and foot rotations were accounted for or when an alternative tendon line of action was used either separately (effect size (ES), 0.46 and 0.58, respectively; P > 0.05) or together (ES, 0.89; P > 0.05). TE-derived moment arms were smaller than GEO-derived moment arms (ES, 0.68-4.86, varying by angle) before accounting for sources of error. However, these differences decreased after error correction (ES, 0.09-1.20, P > 0.05). Nonetheless, the shape of the moment arm-joint angle relation was curvilinear for TE but linear for GEO. CONCLUSIONS Of all methodological modifications, accounting for tendon length changes had the largest effect on TA moment arm estimates. We conclude that the TE method is viable to determine TA moment arms as long as changes in tendon length are accounted for.