Stephen Atkins

The effect of three different (-135°C) whole body cryotherapy exposure durations on elite rugby league players.

Background Whole body cryotherapy (WBC) is the therapeutic application of extreme cold air for a short duration. Minimal evidence is available for determining optimal exposure time. Purpose To explore whether the length of WBC exposure induces differential changes in inflammatory markers, tissue oxygenation, skin and core temperature, thermal sensation and comfort. Method This study was a randomised cross over design with participants acting as their own control. Fourteen male professional first team super league rugby players were exposed to 1, 2, and 3 minutes of WBC at −135°C. Testing took place the day after a competitive league fixture, each exposure separated by seven days. Results No significant changes were found in the inflammatory cytokine interleukin six. Significant reductions (p<0.05) in deoxyhaemoglobin for gastrocnemius and vastus lateralis were found. In vastus lateralis significant reductions (p<0.05) in oxyhaemoglobin and tissue oxygenation index (p<0.05) were demonstrated. Significant reductions (p<0.05) in skin temperature were recorded. No significant changes were recorded in core temperature. Significant reductions (p<0.05) in thermal sensation and comfort were recorded. Conclusion Three brief exposures to WBC separated by 1 week are not sufficient to induce physiological changes in IL-6 or core temperature. There are however significant changes in tissue oxyhaemoglobin, deoxyhaemoglobin, tissue oxygenation index, skin temperature and thermal sensation. We conclude that a 2 minute WBC exposure was the optimum exposure length at temperatures of −135°C and could be applied as the basis for future studies.

Power output of field-based downhill mountain biking

Abstract The purpose of this study was to assess the power output of field-based downhill mountain biking. Seventeen trained male downhill cyclists (age 27.1 ± 5.1 years) competing nationally performed two timed runs of a measured downhill course. An SRM powermeter was used to simultaneously record power, cadence, and speed. Values were sampled at 1-s intervals. Heart rates were recorded at 5-s intervals using a Polar S710 heart rate monitor. Peak and mean power output were 834 ± 129 W and 75 ± 26 W respectively. Mean power accounted for only 9% of peak values. Paradoxically, mean heart rate was 168 ± 9 beats · min−1 (89% of age-predicted maximum heart rate). Mean cadence (27 ± 5 rev · min−1) was significantly related to speed (r = 0.51; P < 0.01). Analysis revealed an average of 38 pedal actions per run, with average pedalling periods of 5 s. Power and cadence were not significantly related to run time or any other variable. Our results support the intermittent nature of downhill mountain biking. The poor relationships between power and run time and between cadence and run time suggest they are not essential pre-requisites to downhill mountain biking performance and indicate the importance of riding dynamics to overall performance.

An analysis of elite coaches’ engagement with performance analysis services (match, notational analysis and technique analysis)

Performance analysis has become increasingly more accessible to coaches across many levels of sport (Blaze et al 2004). The primary aim of this study was to investigate how performance analysis tools are used by elite sports coaches. A stratified sample of forty-six elite professional and semi-professional coaches were selected to complete an online-survey relating to their engagement with match, notational and technique analysis. Most coaches (68%) would be provided with a DVD or edited clips after every game, whilst 16% would receive this service following most games. Over 50% of coaches will use performance analysis tools to provide video clips for other coaches and their support staff (64%); provide a video of the opposition (68%); collate quantitative game data (64%); and use as a motivational DVD (55%). Just under half of the coaches (43%) would use some form of live coding and analysis during games, whilst 39% would also receive a written match report including game statistics. Performance analysis information informed the coaches’ short term planning (93%), medium term planning (80%) and long term planning (70%). 91% of coaches identified that their coaching philosophy would impact on their selection of KPI’s, whilst 43% also identified that their ‘gut instinct’ would often impact on their selection. The key findings from this study have provided specific insight relating to how and why elite coaches engage with performance analysts. In particular, these findings inform specifically on how performance analysis impacts on their coaching practices within a number of different contexts.

The Presence of Bilateral Imbalance of the Lower Limbs in Elite Youth Soccer Players of Different Ages

Abstract Atkins, S, Bentley, I, Hurst, H, Sinclair, J, and Hesketh, C. The presence of bilateral imbalance of the lower limbs in elite youth soccer players of different ages. J Strength Cond Res 30(4): 1007–1013, 2016—The aim of this study was to examine bilateral differences in ground reaction forces (GRF), measured during a deep squat (DS) exercise, in a population of elite youth soccer players. Bilateral muscle balance is a key component in promoting musculoskeletal health of performers, yet there is a limited evidence base investigating such imbalances in youth. Seventy-four subjects were assigned to performance groups according to chronological age (younger than 13, 14, 15, 16, 17 years). Analysis of physical maturity status revealed that very few players were classified as “early” or “late” maturers. Players completed an overhead DS exercise, as part of preseason functional movement screening. Peak GRF were assessed using a twin force plate system. Significant differences (p ⩽ 0.05) were identified between right and left side peak GRF for all groups except the youngest (U13) and oldest (U17). Nondominant “sides” showed the highest levels of PGRF across all groups. The magnitude of PGRF was not significantly different both within and between groups, except for the left side in the U13 to U15 groups (p = 0.04). Results from this study show that performance asymmetry is marked in adolescence. There seems a “trigger point” during the early stage of adolescence, when bilateral imbalances become marked. These differences do seem to reduce during the later stages of adolescence. Correct attention to focussed training, designed to remediate any imbalance, is warranted in adolescent groups. This is important with respect of the key associations between bilateral asymmetry and risk of injury.

Electromyographic Response of Global Abdominal Stabilizers in Response to Stable- and Unstable-Base Isometric Exercise

Abstract Atkins, SJ, Bentley, I, Brooks, D, Burrows, MP, Hurst, HT, and Sinclair, JK. Electromyographic response of global abdominal stabilizers in response to stable- and unstable-base isometric exercise. J Strength Cond Res 29(6): 1609–1615, 2015—Core stability training traditionally uses stable-base techniques. Less is known as to the use of unstable-base techniques, such as suspension training, to activate core musculature. This study sought to assess the neuromuscular activation of global core stabilizers when using suspension training techniques, compared with more traditional forms of isometric exercise. Eighteen elite level, male youth swimmers (age, 15.5 ± 2.3 years; stature, 163.3 ± 12.7 cm; body mass, 62.2 ± 11.9 kg) participated in this study. Surface electromyography (sEMG) was used to determine the rate of muscle contraction in postural musculature, associated with core stability and torso bracing (rectus abdominus [RA], external obliques [EO], erector spinae [ES]). A maximal voluntary contraction test was used to determine peak amplitude for all muscles. Static bracing of the core was achieved using a modified “plank” position, with and without a Swiss ball, and held for 30 seconds. A mechanically similar “plank” was then held using suspension straps. Analysis of sEMG revealed that suspension produced higher peak amplitude in the RA than using a prone or Swiss ball “plank” (p = 0.04). This difference was not replicated in either the EO or ES musculature. We conclude that suspension training noticeably improves engagement of anterior core musculature when compared with both lateral and posterior muscles. Further research is required to determine how best to activate both posterior and lateral musculature when using all forms of core stability training.

Agreement between Polar and SRM mobile ergometer systems during laboratory-based high-intensity, intermittent cycling activity

Abstract The purpose of this study was to assess the agreement between two mobile cycle ergometer systems for recording high-intensity, intermittent power output. Twelve trained male cyclists (age 31.4 ± 9.8 years) performed a single 3 min intermittent cycle test consisting of 12 all-out efforts, separated by periods of passive recovery ranging from 5 to 15 s. Power output was recorded using a Polar S710 heart rate monitor and power sensor kit and an SRM Powercrank system for each test. The SRM used torque and angular velocity to calculate power, while the S710 used chain speed and vibration to calculate power. Significant differences (P < 0.05) in power were found at 8 of the 12 efforts. A significant difference (P = 0.001) was also found when power was averaged over all 12 intervals. Mean power was 556 ± 102 W and 446 ± 61 W for the SRM and S710 respectively. The S710 underestimated power by an average of 23% with random errors of */÷ 24% when compared with the SRM. Random errors ranged from 36% to 141% with a median of 51%. The results indicate there was little agreement between the two systems and that the Polar S710 did not provide a valid measure of power during intermittent cycling activity when compared with the SRM. Power recorded by the S710 system was influenced greatly by chain vibration and sampling rates.

The Effects of Barefoot and Shod Running on Limb and Joint Stiffness Characteristics in Recreational Runners.

ABSTRACT The authors aimed to determine the effects of barefoot (BF) and several commercially available barefoot-inspired (BFIS) footwear models on limb and joint stiffness characteristics compared with conventional footwear (CF). Fifteen male participants ran over a force platform at 4.0 m.s−1, in BF, BFIS, and CF conditions. Measures of limb and joint stiffness were calculated for each footwear. The results indicate that limb and knee stiffness were greater in BF and minimalist BFIS than in CF. CF and more structured BFIS were associated with a greater ankle stiffness compared with BF and minimalist BFIS. These findings serve to provide further insight into the susceptibility of runners to different injury mechanisms as a function of footwear.

Measuring the Workload of Mixed Martial Arts using Accelerometry, Time Motion Analysis and Lactate

Tri-axial accelerometry has previously been shown to provide a reliable technique for the assessment of MMA specific activities during isolated training movements. However, this method has yet to be used for the analysis of competition demands. Six male MMA trained participants took part in a single simulated MMA bout each comprising of 3 rounds of 5 minutes with 1 minute rest between rounds. Participants wore a tri-axial accelerometer positioned between the T3-T4 vertebrae in a harness. Mean accumulated player load (PLdACC) and mean accumulated player load per minute (PLdACC.min-1) were calculated for each round and for the bout overall. Capillary blood lactate samples were also taken prior to warm up, post warm up, upon completion of each round and 5 minutes post bout whilst video based time motion analysis was completed post hoc. PLdACC was 224.32 ± 26.59 au, whilst PLdACC.min-1 was 14.91 ± 1.78 au. Participants had a mean post bout lactate of 9.25 ± 2.96 mmol.L whilst there was significant differences in lactate levels across all six sampling points. The group was found to have a work rest ratio (W:R) of 1:1.01 whilst a significant difference was found between bout winners and bout losers in terms of the amount of successful takedowns.

The influence of different footwear on 3-D kinematics and muscle activation during the barbell back squat in males

Abstract The barbell back squat is commonly used by athletes participating in resistance training. The barbell squat is typically performed using standard athletic shoes, or specially designed weightlifting footwear, although there are now a large number of athletes who prefer to squat barefoot or in barefoot-inspired footwear. This study aimed to determine how these footwear influence 3-D kinematics and muscle activation potentials during the barbell back squat. Fourteen experienced male participants completed squats at 70% 1 rep max in each footwear condition. 3-D kinematics from the torso, hip, knee and ankle were measured using an eight-camera motion analysis system. In addition, electromyographical (EMG) measurements were obtained from the rectus femoris, tibialis anterior, gastrocnemius, erector spinae and biceps femoris muscles. EMG parameters and joint kinematics were compared between footwear using repeated-measures analyses of variance. Participants were also asked to subjectively rate which footwear they preferred when performing their squat lifts; this was examined a chi-squared test. The kinematic analysis indicated that, in comparison to barefoot the running shoe was associated with increased squat depth, knee flexion and rectus femoris activation. The chi-squared test was significant and showed that participants preferred to squat barefoot. This study supports anecdotal evidence of athletes who prefer to train barefoot or in barefoot-inspired footwear although no biomechanical evidence was found to support this notion.

Three-dimensional kinematic correlates of ball velocity during maximal instep soccer kicking in males.

Abstract Achieving a high ball velocity is important during soccer shooting, as it gives the goalkeeper less time to react, thus improving a players chance of scoring. This study aimed to identify important technical aspects of kicking linked to the generation of ball velocity using regression analyses. Maximal instep kicks were obtained from 22 academy-level soccer players using a 10-camera motion capture system sampling at 500 Hz. Three-dimensional kinematics of the lower extremity segments were obtained. Regression analysis was used to identify the kinematic parameters associated with the development of ball velocity. A single biomechanical parameter; knee extension velocity of the kicking limb at ball contact Adjusted R2 = 0.39, p ≤ 0.01 was obtained as a significant predictor of ball-velocity. This study suggests that sagittal plane knee extension velocity is the strongest contributor to ball velocity and potentially overall kicking performance. It is conceivable therefore that players may benefit from exposure to coaching and strength techniques geared towards the improvement of knee extension angular velocity as highlighted in this study.