Philip Graham-Smith

Muscle fatigue induced by exercise simulating the work rate of competitive soccer

Fatigue represents a reduction in the capability of muscle to generate force. The aim of the present study was to establish the effects of exercise that simulates the work rate of competitive soccer players on the strength of the knee extensors and knee flexors. Thirteen amateur soccer players (age 23.3±3.9 years, height 1.78±0.05 m, body mass 74.8±3.6 kg; mean±s) were tested during the 2000–2001 soccer season. Muscle strength of the quadriceps and hamstrings was measured on an isokinetic dynamometer. A 90 min soccer-specific intermittent exercise protocol, incorporating a 15 min half-time intermission, was developed to provide fatiguing exercise corresponding in work rate to a game of soccer. The exercise protocol, performed on a programmable motorized treadmill, consisted of the different intensities observed during soccer match-play (e.g. walking, jogging, running, sprinting). Muscle strength was assessed before exercise, at half-time and immediately after exercise. A repeated-measures analysis of variance showed significant reductions (P <0.001) in peak torque for both the quadriceps and hamstrings at all angular velocities (concentric: 1.05, 2.09, 5.23 rad · s−1; eccentric: 2.09 rad · s−1). The peak torque of the knee extensors (KE) and knee flexors (KF) was greater before exercise [KE: 232±37, 182±34, 129±27, 219±41 N · m at 1.05, 2.09 and 5.23 rad · s−1 (concentric) and 2.09 rad · s−1 (eccentric), respectively; KF: 126±20, 112±19, 101±16, 137±23 N · m] than at half-time (KE: 209±45, 177±35, 125±36, 214±43 N · m; KF: 114±31, 102±20, 92±15, 125±25 N · m) and greater at half-time than after exercise (KE: 196±43, 167±35, 118±24, 204±43 N · m; KF: 104±25, 95±21, 87±13, 114±27 N · m). For the hamstrings : quadriceps ratio, significant changes were found (P <0.05) for both legs, the ratio being greater before than after exercise. For fast : slow speed and left : right ratios, no significant changes were found. We conclude that there is a progressive reduction in muscle strength that applies across a range of functional characteristics during exercise that mimics the work rate in soccer.

A three-dimensional kinematic analysis of the long jump take-off

The long jump has been widely studied in recent years. Two models exist in the literature which define the relationship between selected variables that affect performance. Both models suggest that the critical phase of the long jump event is the touch-down to take-off phase, as it is in this phase that the necessary vertical velocity is generated. Many three dimensional studies of the long jump exist, but the only studies to have reported detailed data on this phase were two-dimensional in nature. In these, the poor relationships obtained between key variables and performance led to the suggestion that there may be some relevant information in data in the third dimension. The aims of this study were to conduct a three-dimensional analysis of the touch-down to take-off phase in the long jump and to explore the interrelationships between key variables. Fourteen male long jumpers were filmed using three-dimensional methods during the finals of the 1994 (n  =  8) and 1995 (n  =  6) UK National Championships. Various key variables for the long jump were used in a series of correlational and multiple regression analyses. The relationships between key variables when correlated directly one-to-one were generally poor. However, when analysed using a multiple regression approach, a series of variables was identified which supported the general principles outlined in the two models. These variables could be interpreted in terms of speed, technique and strength. We concluded that in the long jump, variables that are important to performance are interdependent and can only be identified by using appropriate statistical techniques. This has implications for a better understanding of the long jump event and it is likely that this finding can be generalized to other technical sports skills.

Variation in Pelvic Morphology May Prevent the Identification of Anterior Pelvic Tilt

Abstract Pelvic tilt is often quantified using the angle between the horizontal and a line connecting the anterior superior iliac spine (ASIS) and the posterior superior iliac spine (PSIS). Although this angle is determined by the balance of muscular and ligamentous forces acting between the pelvis and adjacent segments, it could also be influenced by variations in pelvic morphology. The primary objective of this anatomical study was to establish how such variation may affect the ASIS-PSIS measure of pelvic tilt. In addition, we also investigated how variability in pelvic landmarks may influence measures of innominate rotational asymmetry and measures of pelvic height. Thirty cadaver pelves were used for the study. Each specimen was positioned in a fixed anatomical reference position and the angle between the ASIS and PSIS measured bilaterally. In addition, side-to-side differences in the height of the innominate bone were recorded. The study found a range of values for the ASIS-PSIS of 0–23 degrees, with a mean of 13 and standard deviation of 5 degrees. Asymmetry of pelvic landmarks resulted in side-to-side differences of up to 11 degrees in ASIS-PSIS tilt and 16 millimeters in innominate height. These results suggest that variations in pelvic morphology may significantly influence measures of pelvic tilt and innominate rotational asymmetry.

The effect of unstable sandals on instability in gait in healthy female subjects.

Unstable footwear generally lacks thorough peer-review published research to support concepts and marketing claims. The purpose of this study was to investigate the instability induced by four (FitFlop, Masai Barefoot Technology, Reebok Easy-Tone and Skechers Tone-Ups) commercially available unstable sandals and one stable control sandal (Earth) in walking in 15 females (mean±SD age was 29±6.7 years, mass 62.6±6.9kg and height 167.1±4.2cm). Three-dimensional motion with synchronised electromyography and kinetic data were collected. Walking speed and step length remained consistent between conditions, however double support time decreased in Masai Barefoot Technology. Centre of pressure data identified no consistent difference between the stable control and the unstable sandals, however Masai Barefoot Technology reduced the anterior-posterior range of centre of pressure. Muscle activity differed significantly at the ankle in the unstable footwear. FitFlop, Reebok and Skechers increased peroneal activity during pre-swing, whereas Masai Barefoot Technology increased medial gastrocnemius and decreased tibialis anterior activity in loading response and mid-stance. The larger rocker sole of the Masai Barefoot Technology altered gait and muscle activation with regard to braking and progression in the sagittal plane. Reebok, Skechers and FitFlop, with softer, less stable foreparts increased evertor action at toe-off, having their effect in the coronal plane. The study highlighted that any instability induced by the shoes is design-specific.

The Validity of the Nordic Hamstring Lower for a Field-Based Assessment of Eccentric Hamstring Strength

CONTEXT Hamstring injury-risk assessment has primarily been investigated using isokinetic dynamometry. However, practical issues such as cost and availability limit the widespread application of isokinetics for injury-risk assessment; thus, field-based alternatives for assessing eccentric hamstring strength are needed. OBJECTIVE The aim of this study was to investigate the validity of the angle achieved during Nordic hamstring lowers (break-point angle) as a field-based test for eccentric hamstring strength. DESIGN Exploratory study. SETTING Laboratory. PARTICIPANTS Sixteen male (n = 7) and female (n = 9) soccer players (mean ± SD age 24 ± 6 y, height 1.77 ± 0.12 m, and body mass 68.5 ± 16.5 kg) acted as subjects for the study. MAIN OUTCOME MEASURES The authors explored relationships between the Nordic break-point angle (the point at which the subject can no longer resist the increasing gravitational moment during a Nordic hamstring lower) measured from video and isokinetic peak torque and angle of peak torque of right- and left-knee flexors. RESULTS The results revealed a meaningful relationship between eccentric knee-flexor peak torque (average of right and left limbs) and the Nordic break-point angle (r = -.808, r2 = 65%, P < .00001). However, there was a weak relationship observed (r = .480, r2 = 23%, P = .06) between break-point angle and the angle of peak torque (average of right and left limbs). CONCLUSIONS The results suggest that the break-point angle achieved during Nordic hamstring lowers could be used as a field-based assessment of eccentric hamstring strength.

A comparison of plantar pressures in a standard flip-flop and a FitFlop using bespoke pressure insoles

Purpose: The study was undertaken to compare plantar pressures in a Havaiana flip-flop to a FitFlop, a flip-flop with a multi-density midsole designed to induce instability. It was hypothesised that in the Havaiana the toes are used to ‘grip’ the shoe in swing and the loose upper and thin sole provide limited protection to the foot, producing higher plantar pressures than the FitFlop. Methods: Twenty female subjects walked in the footwear conditions while a bespoke instrumented insole quantified plantar pressures. Data analysis grouped sensors into regions for the heel, 1st metatarsophalangeal joint and hallux to isolate pressures that have been linked to comfort and symptoms reportedly alleviated in the FitFlop. Additional analysis was undertaken to measure hallux ‘gripping’ during swing. Results: Significant reductions in plantar pressures in the FitFlop, particularly in peak pressure in the heel (3.6%) and pressure-time integral in the 1stmetatarsophalangeal joint (12.0%) were identified. These findings were attributed to the thicker midsole with different ethylene vinyl acetate (EVA) construction and a redistribution of load to the midfoot where contact area increased by 19.9% compared to the Havaiana. Also evident were reductions in anterior-posterior centre of pressure velocity in the FitFlop, attributed to its softer midfoot delaying progression. Hallux variables identified reductions in time spent ‘gripping’ as well as the magnitude of force applied by the hallux in swing in the FitFlop. Conclusions: Findings from the study identify that the FitFlop reduces pressure in key areas of the foot which are associated with walking comfort as well as clinical conditions. The ‘gripping’ mechanism postulated to hold flip-flops on is lessened in the FitFlop, potentially reducing the likelihood of overuse injuries.

The Role of Eccentric Strength in 180° Turns in Female Soccer Players

Previous studies have reported an association between eccentric strength (ECC-STR) and change of direction (COD) ability. Little is known about how ECC-STR facilitates COD maneuvers. The aim of this study was to examine the role of ECC-STR during a 180° COD task in 18 female soccer players. Each player performed six trials of a 180° COD task whereby three-dimensional motion data from 10 Qualisys Pro-Reflex infrared cameras (240 Hz) and ground reaction forces (GRFs) from two AMTI force platforms (1200 Hz) were collected. Relative eccentric knee extensor (ECC-EXT) and flexor (ECC-FLEX) peak torque was collected from both limbs at 60°·s−1 using a Kin Com isokinetic dynamometer. Large correlations were revealed between COD performance (time to complete 5 m approach, 180° turn, 5 m return) and ECC-EXT (R = −0.674) and ECC-FLEX (R = −0.603). Moderate to large correlations were observed between approach velocity (AV) and COD performance (R = −0.484) and ECC-EXT (R = 0.724). Stronger participants (n = 9) recorded significantly (p < 0.05) faster AV (4.01 ± 0.18 vs. 3.74 ± 0.24 m·s−1, d = 1.27) and a greater reduction in velocity (−1.55 ± 0.17 vs. −1.37 ± 0.21 m·s−1, d = −0.94) during penultimate contact than weaker (n = 9) subjects. Greater ECC-STR is associated with faster COD performance in female soccer players, as stronger players are better able to decelerate during penultimate contact from faster approach velocities.

Does flip-flop style footwear modify ankle biomechanics and foot loading patterns?

BackgroundFlip-flops are an item of footwear, which are rubber and loosely secured across the dorsal fore-foot. These are popular in warm climates; however are widely criticised for being detrimental to foot health and potentially modifying walking gait. Contemporary alternatives exist including FitFlop, which has a wider strap positioned closer to the ankle and a thicker, ergonomic, multi-density midsole. Therefore the current study investigated gait modifications when wearing flip-flop style footwear compared to barefoot walking. Additionally walking in a flip-flop was compared to that FitFlop alternative.MethodsTesting was undertaken on 40 participants (20 male and 20 female, mean ± 1 SD age 35.2 ± 10.2 years, B.M.I 24.8 ± 4.7 kg.m-2). Kinematic, kinetic and electromyographic gait parameters were collected while participants walked through a 3D capture volume over a force plate with the lower limbs defined using retro-reflective markers. Ankle angle in swing, frontal plane motion in stance and force loading rates at initial contact were compared. Statistical analysis utilised ANOVA to compare differences between experimental conditions.ResultsThe flip-flop footwear conditions altered gait parameters when compared to barefoot. Maximum ankle dorsiflexion in swing was greater in the flip-flop (7.6 ± 2.6°, p = 0.004) and FitFlop (8.5 ± 3.4°, p < 0.001) than barefoot (6.7 ± 2.6°). Significantly higher tibialis anterior activation was measured in terminal swing in FitFlop (32.6%, p < 0.001) and flip-flop (31.2%, p < 0.001) compared to barefoot. A faster heel velocity toward the floor was evident in the FitFlop (-.326 ± .068 m.s-1, p < 0.001) and flip-flop (-.342 ± .074 m.s-1, p < 0.001) compared to barefoot (-.170 ± .065 m.s-1). The FitFlop reduced frontal plane ankle peak eversion during stance (-3.5 ± 2.2°) compared to walking in the flip-flop (-4.4 ± 1.9°, p = 0.008) and barefoot (-4.3 ± 2.1°, p = 0.032). The FitFlop more effectively attenuated impact compared to the flip-flop, reducing the maximal instantaneous loading rate by 19% (p < 0.001).ConclusionsModifications to the sagittal plane ankle angle, frontal plane motion and characteristics of initial contact observed in barefoot walking occur in flip-flop footwear. The FitFlop may reduce risks traditionally associated with flip-flop footwear by reducing loading rate at heel strike and frontal plane motion at the ankle during stance.

Using rhythmicity to promote performance in horizontal jumps: an exemplar of the need for individually-tailored interventions.

1 The current study compared and contrasted the optimal regulation of stride patterns in the 2 horizontal jumping events for 6 British athletes of international standard. Long jump and 3 triple jump approach data were collected over a 3-year period in international and domestic 4 competitions and considered against the distances achieved. Results suggest that on approach 5 to the take-off board, the majority of athletes’ jumps of greater length (intra-athlete) are 6 associated with a low variability, rhythmical footfall. Given the variable approach strategies 7 used by the athletes in question, and consequently the theoretical implications the data set 8 holds, tentative conclusions are drawn regarding the means by which scientists and coaches 9 should assess and design suitable performance focused interventions for elite performers 10 based on individual responses. 11 12 13 14 15 16 17 18 19 20 21 22 23 Horizontal Jump Performance Using Rhythmicity to Promote Performance in Horizontal Jumps: An Exemplar of the Need 1 for Individually-Tailored Interventions 2 Determining how skilled performers execute goal-directed behaviours and the means 3 that enable performance to be enhanced is an essential role which applied sport psychologists 4 often conduct in partnership with other scientists. In doing so, scientist-practitioners often 5 seek guidance from the prevailing theoretical and/or empirical paradigms before applying this 6 knowledge to the practical problem at hand. However, this may sometimes take thinking in 7 an erroneous or less than optimum direction, especially in the special cases of elite 8 performers. In this regard, recent evidence suggests that there are significant advantages to 9 examining how skilled performers organise movement patterns on an intra-individual basis, 10 despite commonalities in patterns of co-ordination being evident in participants of similar 11 ability. For example, Chow, Davids, Button, and Koh, (2006) stated that if skilled 12 participants are grouped together for the purposes of movement analysis, effects of interest, 13 such as control strategies may become masked. 14 Support for pursuing applied sport psychology on a case-by-case basis is illustrated by 15 an increasing number of studies that demonstrated individual-specific findings with reference 16 to performers’ coordination, their responses to appropriate sources of information for 17 instruction and adaptation to physical stress. For example, Beavan, Gill, and Cook (2008a) 18 demonstrated that professional rugby union players with broadly similar training backgrounds 19 responded to group-prescribed resistance training through individual hormonal responses. It 20 was determined that certain players responded positively to some training stresses, but not to 21 other forms of resistance training. In a 3-week cross-over design, the same players alternated 22 between sessions that produced high and low levels of testosterone. It was found that 23 favoured exercise selection elicited players’ maximum testosterone response and resulted in a 24 statistically significant strength gain. However, when the less favoured protocol was used, 25 Horizontal Jump Performance there was either no change, or a significant decline in tested strength (Beavan, Gill, & Cook, 1 2008b). Such individualised hormonal responses to training adaptations in professional sport 2 lend credence to the claim that advanced performers should be investigated on an individual 3 basis. 4 Further support for this contention is provided by examples of empirical research that 5 advocated the application of generic instructional principles to elite groups with—in some 6 cases—less than optimum results. Research carried out with shooters (e.g., rifle, pistol, and 7 archery) by Helin, Sihvonen, and Hanninen, (1987) and Landers, Christina, Hatfield, Daniels 8 and Doyle (1980) suggested that shooters performed to an optimised level when they shot in9 between heartbeats when the cardiac cycle is in diastole, or in what is termed the inter-beat 10 interval (IBI). However, analysis of case study data of six elite-level shooters conducted by 11 Bellamy, Collins, Holmes and Loze (1999) indicated that there is insufficient evidence to 12 advocate a universal strategy of shooting during diastole in elite shooters, since four of the 13 six shooters examined actually shot on the beat. Rather, they suggested the essential need for 14 checks that could detect individual patterns associated with better performance. Whilst this 15 example is somewhat dated, it is uncertain whether the application of generic instructions to 16 elite or advanced performers, albeit derived from peer-reviewed empirical work would 17 automatically result in an improvement to personal performance. 18 A more recent example of the contrasting instructional content of pre-performance 19 routines (PPRs) among elite golfers (i.e., mean handicap of +1.5) was uncovered by 20 Cotterrill, Sanders, and Collins (2010). Whilst the content and firing modality of PPRs has 21 been well researched in relation to self-paced skills (Singer, 2002), research conducted by 22 Cotterrill et al. (2010) showed that the development of a PPR for an elite golfer is 23 idiosyncratic; contingent upon their coping resources; factors that constitute their 24 personalities; and a tendency to appraise the context of each golf shot prior to task execution. 25 Horizontal Jump Performance Accordingly, we suggest that working uncritically from theory to intervention is not an 1 appropriate strategy for groups of advanced learners. 2 In light of these two examples (shooting & golf), it is important to reflect upon the 3 work of Newell, Liu, and Mayer-Kress (2005). Specifically, they proposed that different 4 types of information are differentially effective for athletes, and that the efficacy of 5 alternative sources of information is dependent on the task and the skill level of the learner. 6 Consequently, it is unlikely that an athlete’s potential will be maximised if a ‘one instruction 7 fits all’ approach is used. Therefore, the onus is on applied scientists to determine the most 8 effective sources of information to communicate with and inform athletes’ motor systems. 9 For example, in a study that provided concurrent auditory feedback to gymnasts on the 10 pommel horse, body segment alignment improved by 2.3% between the experimental and 11 control groups. Researchers concluded that auditory feedback provided in real-time could be 12 used to correct complex movements (Baudry, Leroy, Thouvarecq, & Chollet, 2006) as 13 opposed to the more commonly applied video techniques. Interestingly, anecdotal evidence 14 suggested that experienced horizontal jumps coaches could listen to the footfall of their 15 athletes, whilst looking in the opposite direction, and were able to confidently assert whether 16 their athlete had jumped well, or not (Moore, 2006). 17 Whilst it seems that some horizontal jumps coaches have become aware of, and 18 utilise, the rhythm engendered by the auditory output of an athlete’s footfall signature on 19 approach to the take-off board, there is interesting empirical research that has demonstrated 20 the beneficial effect of utilising an auditory output to augment visual information. In a 21 complex series of five experiments Vroomen and de Gelder (2000) demonstrated that 22 perceptual organisation in the auditory modality impacted upon perceptual accuracy in the 23 visual modality. Specifically, a high tone embedded in a series of low tones improved 24 detection of a visual target, when the visual target was presented at the same time – provided 25 Horizontal Jump Performance that the tone was abrupt and distinct from background noise or contaminating melodies. 1 These studies demonstrated that auditory stimuli can be used to enhance the detection of 2 visual information. Therefore, it is possible that a holistic rhythm of an athlete’s footfall prior 3 to contact with the take-off board may serve as an aid to improve foot-to-board accuracy – 4 provided an athlete’s footfall patterns are deemed to be relatively stable. 5 Whilst some athletes might not find this modality of movement correction useful, data 6 presented in this paper provide an opportunity for scientists, applied practitioners, and 7 coaches to consider the implications of working with elite performers through an exemplar of 8 this ‘individualised’ approach. Specifically, the applicability of prevailing theoretical 9 paradigms pertaining to the approach and preparation phases of horizontal jumps is critiqued 10 through consideration of data obtained from a cohort of elite performers. 11 Horizontal Jumps: Event demands 12 For athletes participating in horizontal jumps (HJ) the apparent difficulty associated 13 with executing the task lies in direct contrast to the simplicity of the objective. In particular, 14 the challenge rests in the trade-off between maintaining peak horizontal velocity (athletes 15 typically achieve peak horizontal velocities at take-off of 9.4 m/s for men, and 8.6 m/s for 16 women; see Linthorne, 2007) and being accurate on to the take-off board. To maximise the 17 measured distance, the space between the jump take-off and the edge of the take-off board 18 must be minimised. In addition, the athlete is required to create good ‘lift’ at take-off, 19 generating vertical impulse by accelerating body parts upwards during the final contact with 20 the board without employing large braking forces. A key factor in generating vertical lift is 21 the transference of horizontal velocity accrued on the run-up. Therefore, accuracy onto the 22 take-off board, at speed, is critical to eventual distance achieved (Hay, Miller, & Canterna, 23 1986). 24 Horizontal Jump Performance At an elite level the difficulty of “hitting the board” in HJ is exemplified by 1 1 participant in this investigation, an elite horizontal jumper, who had 10 years of

Testing a mechanical protocol to replicate impact in walking footwear

Impact testing is commonly undertaken to quantify the shock absorption characteristics of footwear. The current widely reported mechanical testing method mimics the vertical heel velocity at touchdown and effective mass of the lower limb recorded in running. This therefore results in a greater impact energy than would be expected at touchdown in walking. Despite this mismatch, the methodology is utilised to quantify the shock absorption properties of running and walking footwear alike. The current work modifies the mechanical testing methodology to replicate the kinematics, specifically the vertical heel velocity, identified in walking footwear. Kinematic and kinetic data was collected for 13 subjects walking in four different styles of footwear used for walking (trainer, oxford shoe, flip-flop and triple-density sandal). The kinematic data was utilised to quantify heel velocity at touchdown and accelerometer and force plate data was utilised to estimate the effective mass of the lower limb. When walking in the toe-post style footwear significantly faster vertical heel velocity toward the floor was recorded compared to barefoot and the other footwear styles (Figure ​(Figure11 for example flip-flop: 0.36±0.05m.s-1 compared to trainer: 0.18±0.06m.s-1). The mechanical protocol was adapted by altering the mass and drop height from 10.6-17.3 kg and 2-7 mm, compared to the original protocol of 8.45 kg dropped from 50 mm. As expected, the adapted mechanical protocol produced significantly lower peak force and accelerometer values than the ASTM protocol (p <.001). These values more closely resembled those recorded in walking. The mean difference between the human and modified protocol was 12.7±17.5% (p<.001) for peak acceleration and 25.2±17.7% (p=.786) for peak force values. The timing of peak force and acceleration variables was less representative of the real-life data with larger mean differences. This pilot test has demonstrated that the altered mechanical test protocol can more closely replicate loading on the lower limb in walking. Further research should consider more variables related to the shock absorption properties of footwear. The results also demonstrate that testing of material properties of footbeds not only needs to be gait style specific (e.g. running versus walking), but also footwear style specific due to the differences in heel touch-down velocity in footwear styles. Figure 1 Vertical heel velocity towards the floor in the human testing for the four footwear conditions. Triple-density sandal = SA, flip-flop = FF, shoe = SH and trainer = TR and Barefoot (BF). Error bars denote standard deviation across the 13 subjects tested. ...