Ian C. Kenny

Is outcome related to movement variability in golf

The aim of this study was to develop a method to quantify movement variability in the backswing and downswing phase of the golf swing and statistically assess whether there was any relationship between movement variability and outcome variability. Sixteen highly skilled golfers each performed 10 swings wearing retro-reflective markers which were tracked by a three-dimensional (3D) motion analysis system operating at 400 Hz. Ball launch conditions were captured using a launch monitor. Performance variability was calculated for each body marker based on a scalene ellipsoid volume concept which produced a score representative of the 3D variability over the 10 trials. Outcome variability was quantified as the coefficient of variation of ball velocity for the 10 trials. The statistical analysis revealed no significant correlations between performance variability for each marker trajectory and outcome variability. Performance variability in the backswing or downswing was not related to ball velocity variability. It was postulated that individual players used their own strategies in order to control their performance variability, such that it had no effect on outcome variability.

Method analysis of accelerometers and gyroscopes in running gait: A systematic review

To review articles utilising accelerometers and gyroscopes to measure running gait and assess various methodology utilised when doing so. To identify research- and coaching-orientated parameters which have been previously investigated and offer evidence based recommendations as to future methodology employed when investigating these parameters. Electronic databases were searched using key-related terminology such as accelerometer(s) and gyroscope(s) and/or running gait. Articles returned were then visually inspected and subjected to an inclusion and exclusion criteria after which citations were inspected for further relevance. A total of 38 articles were then included in the review. Accelerometers, gyroscopes plus combined units have been successfully utilised in the generation of research-orientated parameters such as head/tibial acceleration, vertical parameters and angular velocity and also coach-orientated parameters such as stride parameters and gait pattern. Placement of sensors closest to the area of interest along with the use of bi/tri- axial accelerometers appear to provide the most accurate results. Accelerometers and gyroscopes have proven to provide accurate and reliable results in running gait measurement. The temporal and spatial running parameters require sensor placement close to the area of interest and the use of bi/triaxial sensors. Post data analysis is critical for generating valid results.

Validation of an electronic jump mat to assess stretch-shortening cycle function

Abstract Kenny, IC, Ó Cairealláin, A, and Comyns, TM. Validation of an electronic jump mat to assess stretch-shortening cycle function. J Strength Cond Res 26(6): 1601–1608, 2012—The purpose of this investigation was to determine the concurrent validity of a commonly used electronic switch mat (ESM), or jump mat, compared with force plate (FP) data. The efficiency of collection and accuracy of data are paramount to athlete and player field testing for the strength and conditioning coach who often has access only to a jump mat. Ten subjects from 5 different sporting backgrounds completed 3 squat jumps (SJs), 3 countermovement jumps (CMJs), and 3 drop jumps (DJs). The jumps were performed on an AMTI FP operating at 1,000 Hz with an ESM positioned on top of the platform. All the subjects were experienced with the protocols involved with jump testing. The resulting absolute errors between FP and ESM data were 0.01, 0.02, and 0.01 m for CMJ, SJ, and DJ heights, respectively. However, the coefficient of variation for the DJ contact time (CT) was 57.25%, CMJ (r = 0.996), and SJ (r = 0.958) heights correlated very strongly with force platform data, and DJ data were not as strong (r = 0.683). Confidence interval tests revealed bias toward CMJ and SJ (p < 0.05). The jump mat can accurately calculate the CMJ height, SJ height, and reactive strength index for all the 3 jump protocols. However, the faster CTs and rapid movements involved in a DJ may limit its reliability when giving measures of CT, flight time, and height jumped for DJs. Strength and conditioning coaches can use such a jump mat device with the confidence that it is accurately producing valid measurements of their athletes performance for CMJ and SJ slow SSC protocols.

Sprinting performance and resistance-based training interventions: a systematic review.

Abstract Bolger, R, Lyons, M, Harrison, AJ, and Kenny, IC. Sprinting performance and resistance-based training interventions: A systematic review. J Strength Cond Res 29(4): 1146–1156, 2015—The purpose of this systematic review was to search the scientific literature for original research, addressing the effects different forms of resistance-based training have on sprinting performance in competitive sprinters. Specific key words (Sprinters OR Sprint) NOT (Rugby, Soccer, Cycling, Swimming, Paralympic, and Nutrition) were used to search relevant databases through November 2013 for related literature. Original research was reviewed using the Physiotherapy Evidence Database scale. Five studies met the inclusion criteria: actively competitive adult male sprinters who participated in a resistance-based intervention (>4 weeks), with outcome measures in the form of 10- to 100-m sprint times. Exclusion criteria included acute studies (<4 weeks), nonsprinting populations, and studies with no performance outcome measures (10- to 100-m sprint times). Three of the 5 studies used both locomotor resistance and fixed plane resistance, whereas the remaining 2 studies used more fixed plane resistance, for example, squat and leg extension. Three of the studies showed a statistical improvement in sprinting performance measures, for example, a decrease in 30-m sprint time (p = 0.044), whereas 1 study showed a decrease in sprinting performance. The analysis concluded that resistance-based training has a positive effect on sprinting performance. Varied input of locomotor resistance and fixed plane resistance has resulted in similar percentage change for sprinting performance. This review adds to the body of knowledge by strongly highlighting the dearth of literature exploring the effects of resistance-based training on sprinting performance in competitive sprinters. The short duration and wide range of exercises implemented in studies to date are of concern, but coaches should not hesitate to implement well-planned resistance programs for their sprint athletes.

Influence of shaft length on golf driving performance

The aim of this study was to determine how shaft length affects golf driving performance. A range of drivers with lengths between 1.168 m and 1.270 m, representing lengths close to the 1.219 m limit imposed by R&A Rules Limited (2008), were assembled and evaluated. Clubhead and ball launch conditions and drive distance and accuracy were determined for seven category 1 golfers (handicaps 0.21 ± 2.41) who performed shots on a purpose-built practice hole. As shaft length increased from 1.168 m to 1.270 m, initial ball velocity increased (+1.8 m/s, P < 0.01). Ball carry (+4.3 m, P = 0.152) also increased, although not significantly so. Furthermore, as shaft length increased, for all club comparisons there was no decrease in accuracy. Ball launch conditions of spin components and launch angle remained unaffected by shaft length. Launch angle increased (0.8°, F = 1.074, P = 0.362) as driver shaft length increased. Our results show that clubhead and ball velocity together with ball carry tended to increase with no loss of accuracy.

Validation of a Full-Body Computer Simulation of the Golf Drive for Clubs of Differing Length

The aim of the present study was to validate a full-body computer simulation of a golfer’s swing for driving clubs. An elite male golfer performed 24 shots in a laboratory, comprised of 8 trials using each of three drivers of different shaft length (46″, 48″, & 50″). A 5-camera MACTM system operating at 240 Hz collected kinematic data which was subsequently used to drive the model utilising ADAMS/LifeMOD software. Additional skin markers were used for model validation. A large-scale musculoskeletal human model was constructed, with a parametric model of a driver. Inverse and forward dynamics calculations were performed with the imported experimental motion data in order to generate model movement. A commercially available launch monitor recorded experimental eclubhead and launch conditions. There was a very high level of agreement (r=0.995) between experimental kinematic data and the predicted trjectory splines of the model. There was also a high level of correlation (r=0.989) between the model predicted mean values for clubhead speed and the experimental values for each of the club lengths, both demonstrating increased clubhead velocity as club length increased. Muscle contraction force output by the model showed a significant difference (p≤0.001) between driver simulations, demonstrating its capability to illustrate the link between gross muscle force production and club length, as evidenced by the increased force output for the longest shafted club.

Dynamic knee joint mechanics after anterior cruciate ligament reconstruction.

PURPOSE There is scarcity of information on the long-term adaptations in lower limb biomechanics during game-specific movements after anterior cruciate ligament (ACL) reconstruction. Particularly, variables such as knee abduction moments and transverse plane knee motion have not been studied during a game-specific landing and cutting task after ACL reconstruction. The purpose of this study was to compare the hip and knee mechanics between the ACL-reconstructed (ACLr) group and a healthy control group. METHODS Thirty-eight reconstructed athletes (18 ACLr, 18 control) participated in the study. Three-dimensional hip, knee, and ankle angles were calculated during a maximal drop jump land from a 0.30-m box and unanticipated cutting task at 45°. RESULTS During the landing phase, ACLr participants had increased hip flexion (P < 0.003) and transverse plane knee range of motion (P = 0.027). During the cutting phase, the ACLr participants previously injured limb had increased internal knee abduction moment compared with that of the control group (P = 0.032). No significant differences were reported between the previously injured and contralateral uninjured limb. CONCLUSIONS Previously injured participants demonstrated higher knee abduction moment and transverse plane range of motion when compared with those of control participants during a game-specific landing and cutting task.

The Effect of Strength Training on Performance Indicators in Distance Runners.

Abstract Beattie, K, Carson, BP, Lyons, M, Rossiter, A, and Kenny, IC. The effect of strength training on performance indicators in distance runners. J Strength Cond Res 31(1): 9–23, 2017—Running economy (RE) and velocity at maximal oxygen uptake (VV[Combining Dot Above]O2max) are considered to be the best physiological performance indicators in elite distance runners. In addition to cardiovascular function, RE and VV[Combining Dot Above]O2max are partly dictated by neuromuscular factors. One technique to improve neuromuscular function in athletes is through strength training. The aim of this study was to investigate the effect of a 40-week strength training intervention on strength (maximal and reactive strength), VV[Combining Dot Above]O2max, economy, and body composition (body mass, fat, and lean mass) in competitive distance runners. Twenty competitive distance runners were divided into an intervention group (n = 11; 29.5 ± 10.0 years; 72.8 ± 6.6 kg; 1.83 ± 0.08 m) and a control group (n = 9; 27.4 ± 7.2 years; 70.2 ± 6.4 kg; 1.77 ± 0.04 m). During week 0, 20, and 40, each subject completed 3 assessments: physiology (V2 mmol·L−1 BLa, V2 mmol·L−1 BLa [blood lactate], V4 mmol·L−1 BLa, RE, VV[Combining Dot Above]O2max, V[Combining Dot Above]O2max), strength (1 repetition maximum back squat; countermovement jump and 0.3 m drop jump), and body composition (body mass, fat mass, overall lean, and leg lean). The intervention group showed significant improvements in maximal and reactive strength qualities, RE, and VV[Combining Dot Above]O2max, at weeks 20 (p ⩽ 0.05) and 40 (p ⩽ 0.05). The control group showed no significant changes at either time point. There were no significant changes in body composition variables between or within groups. This study demonstrates that 40 weeks of strength training can significantly improve maximal and reactive strength qualities, RE, and VV[Combining Dot Above]O2max, without concomitant hypertrophy, in competitive distance runners.

Determinants of Success in the Olympic Decathlon: Some Statistical Evidence

In a recent communication, Van Damme et al (1) presented a statistical analysis of the performance of world-ranked decathletes, and made inferences about the ability of these athletes to respond uniformly to the demands of the ten events in the decathlon. Their argument was based on an interpretation of the negative correlation in a sample of 600 world-ranked decathletes between the best performance in an event and the overall performance. They used the principle of allocation (2) to argue that excellence in one task may only be attained at the expense of average performance in all other tasks. We present here a complementary view. We considered the 92 decathletes who competed in the last five Olympic games. For this elite sub-sample we found an opposite result to that of Van Damme et al (1): to compete successfully at this level, a uniform, relatively high performance in all individual disciplines is required.

Effects of a Low-Load Gluteal Warm-Up on Explosive Jump Performance

Abstract The purpose of this study was to investigate the effects of a low-load gluteal warm-up protocol on countermovement and squat jump performance. Research by Crow et al. (2012) found that a low-load gluteal warm-up could be effective in enhancing peak power output during a countermovement jump. Eleven subjects performed countermovement and squat jumps before and after the gluteal warm-up protocol. Both jumps were examined in separate testing sessions and performed 30 seconds, and 2, 4, 6 & 8 minutes post warm-up. Height jumped and peak ground reaction force were the dependent variables examined in both jumps, with 6 additional variables related to fast force production being examined in the squat jump only. All jumps were performed on a force platform (AMTI OR6-5). Repeated measures analysis of variance found a number of significant differences (p ≤ 0.05) between baseline and post warm-up scores. Height jumped decreased significantly in both jumps at all rest intervals excluding 8 minutes. Improvement was seen in 7 of the 8 recorded SJ variables at the 8 minute interval. Five of these improvements were deemed statistically significant, namely time to peak GRF (43.0%), and time to the maximum rate of force development (65.7%) significantly decreased, while starting strength (63.4%), change of force in first 100 ms of contraction (49.1%) and speed strength (43.6%) significantly increased. The results indicate that a gluteal warm-up can enhance force production in squat jumps performed after 8 minutes recovery. Future research in this area should include additional warm-up intervention groups for comparative reasons.