Nigel K. Harris

Relationship between sprint times and the strength/power outputs of a machine squat jump.

Strength testing is often used with team-sport athletes, but some measures of strength may have limited prognostic/diagnostic value in terms of the physical demands of the sport. The purpose of this study was to investigate relationships between sprint ability and the kinetic and kinematic outputs of a machine squat jump. Thirty elite level rugby union and league athletes with an extensive resistance-training background performed bilateral concentric-only machine squat jumps across loads of 20% to 90% 1 repetition maximum (1RM), and sprints over 10 meters and 30 or 40 meters. The magnitudes of the relationships were interpreted using Pearson correlation coefficients, which had uncertainty (90% confidence limits) of ∼±0.3. Correlations of 10-meter sprint time with kinetic and kinematic variables (force, velocity, power, and impulse) were generally positive and of moderate to strong magnitude (r = 0.32-0.53). The only negative correlations observed were for work, although the magnitude was small (r = −0.18 to −0.26). The correlations for 30- or 40-meter sprint times were similar to those for 10-meter times, although the correlation with work was positive and moderate (r = 0.35-0.40). Correlations of 10-meter time with kinetic variables expressed relative to body mass were generally positive and of trivial to small magnitude (r = 0.01-0.29), with the exceptions of work (r = −0.31 to −0.34), and impulse (r = −0.34 to −0.39). Similar correlations were observed for 30- and 40-meter times with kinetic measures expressed relative to body mass. Although correlations do not imply cause and effect, the preoccupation with maximizing power output in this particular resistance exercise to improve sprint ability appears problematic. Work and impulse are potentially important strength qualities to develop in the pursuit of improved sprinting performance.

Squat jump training at maximal power loads vs. heavy loads: effect on sprint ability.

Harris, NK, Cronin, JB, Hopkins, WG, and Hansen, KT. Squat jump training at maximal power loads vs. heavy loads: effect on sprint ability. J Strength Cond Res 22(6): 1742-1749, 2008-Training at a load maximizing power output (Pmax) is an intuitively appealing strategy for enhancement of performance that has received little research attention. In this study we identified each subjects Pmax for an isoinertial resistance training exercise used for testing and training, and then we related the changes in strength to changes in sprint performance. The subjects were 18 well-trained rugby league players randomized to two equal-volume training groups for a 7-week period of squat jump training with heavy loads (80% 1RM) or with individually determined Pmax loads (20.0-43.5% 1RM). Performance measures were 1RM strength, maximal power at 55% of pretraining 1RM, and sprint times for 10 and 30 m. Percent changes were standardized to make magnitude-based inferences. Relationships between changes in these variables were expressed as correlations. Sprint times for 10 m showed improvements in the 80% 1RM group (−2.9 ± 3.2%) and Pmax group (−1.3 ± 2.2%), and there were similar improvements in 30-m sprint time (−1.9 ± 2.8 and −1.2 ± 2.0%, respectively). Differences in the improvements in sprint time between groups were unclear, but improvement in 1RM strength in the 80% 1RM group (15 ± 9%) was possibly substantially greater than in the Pmax group (11 ± 8%). Small-moderate negative correlations between change in 1RM and change in sprint time (r ≈ −0.30) in the combined groups provided the only evidence of adaptive associations between strength and power outputs, and sprint performance. In conclusion, it seems that training at the load that maximizes individual peak power output for this exercise with a sample of professional team sport athletes was no more effective for improving sprint ability than training at heavy loads, and the changes in power output were not usefully related to changes in sprint ability.

Power Outputs Of A Machine Squat-jump Across A Spectrum Of Loads

The load that maximizes mechanical power output (Pmax) has received considerable research attention owing to its perceived importance to training prescription. However, it may be that identifying Pmax is of little importance if the difference in power output about Pmax is insubstantial. Additionally, comparing the effect of load on power output between studies is problematic due to various methodological differences. The purpose of this study therefore was to quantify the concentric power output for a machine squat-jump across a spectrum of loads (10–100% of 1 repetition maximum [1RM]). To estimate Pmax load and proximate loads a quadratic was fitted to the power output (Watts) and load (% of 1RM) of 18 well-trained rugby athletes. Pmax for peak and mean power output occurred at 21.6 ± 7.1% of 1RM (mean ± SD) and 39.0 ± 8.6% of 1RM, respectively. A 20% change in load either side of the maximum resulted in a mean decrease of only 9.9% (90% confidence limits ×2.4%) and 5.4% (±0.9%) in peak and mean power respectively; standard deviations about these means (representing individual differences in the decrease) were 6.0% and 2.1%, respectively (90% confidence limits ×/÷1.34). It appears that most athletes have a broad peak in their power profile for peak or mean power. The preoccupation of identifying one load for maximizing power output would seem less meaningful than many practitioners and scientists believe.

Physiological Demands of Competitive Surfing

Abstract Farley, ORL, Harris, NK, and Kilding, AE. Physiological demands of competitive surfing. J Strength Cond Res 26(7): 1887–1896, 2012—This study was a performance analysis of surfing athletes during competitive surfing events in an attempt to inform the development of surfing-specific conditioning. Twelve nationally ranked surfers were fitted with heart rate (HR) monitors and global positioning system (GPS) units and videoed during the heats of 2 sanctioned competitions. Means and SDs represented the centrality and spread of analyzed data. From the 32 videos analyzed, the greatest amount of time spent during surfing was paddling (54 ± 6.3% of the total time) (% TT). The remaining stationary represented 28 ± 6.9% TT, wave riding, and paddling for a wave represented only 8 ± 2% TT and 4 ± 1.5% TT, respectively. Surfers spent 61 ± 7% of the total paddling bouts and 64 ± 6.8% of total stationary bouts between 1 and 10 seconds. The average speed recorded via the GPS for all the subjects was 3.7 ± 0.6 km·h−1, with an average maximum speed of 33.4 ± 6.5 km·h−1 (45 km·h−1 was the highest speed recorded). The average distance covered was 1,605 ± 313 m. The mean HR during the surf competitions was 139 ± 11 b·min−1 (64% HRmax), with a (mean) peak of 190 ± 12 b·min−1 (87% HRmax). Sixty percent TT was spent between 56 and 74% of the age-predicted HR maximum (HRmax), 19% TT >46% HRmax, and approximately 3% TT >83% HRmax. Competitive surfing therefore involves intermittent high-intensity bouts of all out paddling intercalated with relatively short recovery periods and repeated bouts of low-intensity paddling, incorporating intermittent breath holding. Surfing-specific conditioning sessions should attempt to replicate such a profile.

USING THE LOAD-VELOCITY RELATIONSHIP FOR 1RM PREDICTION

Jidovtseff, B, Harris, NK, Crielaard, J-M, and Cronin, JB. Using the load-velocity relationship for 1RM prediction. J Strength Cond Res 25(1): 267-270, 2011-The purpose of this study was to investigate the ability of the load-velocity relationship to accurately predict a bench press 1 repetition maximum (1RM). Data from 3 different bench press studies (n = 112) that incorporated both 1RM assessment and submaximal load-velocity profiling were analyzed. Individual regression analysis was performed to determine the theoretical load at zero velocity (LD0). Data from each of the 3 studies were analyzed separately and also presented as overall group mean. Thereafter, correlation analysis provided quantification of the relationships between 1RM and LD0. Practically perfect correlations (r = ∼0.95) were observed in our samples, confirming the ability of the load-velocity profile to accurately predict bench press 1RM.

Contraction force specificity and its relationship to functional performance

Abstract Best practice for improving strength and power through resistance strength training has been the subject of much research and subsequent conjecture. Much of the conjecture can be attributed to methodological discrepancies. The type of dynamometry used in testing, the training experience of research participants, the specific technique employed in a lift, and the methods of collection and calculation all impact on the final variables of interest. This review examines contraction force specificity by first addressing the methodological issues surrounding our interpretation of the results. Then we address the kinematics and kinetics associated with single and multiple repetitions in relation to the development of strength, power, and functional performance. This discussion provides the delimitations for analysis of subsequent training studies. Finally, recommendations are formulated with the aim of assisting assessment and training practice as well as providing directions for future research. The results of this review suggest that the enhancements in performance resulting from resistance training are context specific in experienced resistance-trained participants. Thus, specific conditioning could be required to achieve improvements in functional performance in this group.

Understanding position transducer technology for strength and conditioning practitioners

STRENGTH AND POWER ASSESSMENTS IN CONDITIONING PRACTICE HAVE TYPICALLY INVOLVED RUDIMENTARY MEASURES SUCH AS 1 REPETITION MAXIMUM. MORE COMPLEX LABORATORY ANALYSIS HAS BEEN AVAILABLE BUT BECAUSE OF THE PRICE AND PORTABILITY OF EQUIPMENT, SUCH ANALYSIS REMAINED IMPRACTICAL TO MOST PRACTITIONERS. RECENTLY, A NUMBER OF DEVICES HAVE BECOME AVAILABLE THAT ARE REASONABLY INEXPENSIVE AND PORTABLE AND OFFER A GREAT DEAL OF INFORMATION THAT CAN BE USED TO GUIDE PROGRAMMING AND TRAINING TO BETTER EFFECT. ONE SUCH DEVICE IS THE LINEAR POSITION TRANSDUCER. THIS ARTICLE DISCUSSES THIS PIECE OF TECHNOLOGY FROM ITS DESIGN TO HOW IT MAY BE USED TO INFORM PRACTICE.

The strength and conditioning practices of strongman competitors.

Winwood, PW, Keogh, JWL, and Harris, NK. The strength and conditioning practices of strongman competitors. J Strength Cond Res 25(11): 3118–3128, 2011—This study describes the results of a survey of the strength and conditioning practices of strongman competitors. A 65-item online survey was completed by 167 strongman competitors. The subject group included 83 local, 65 national, and 19 international strongman competitors. The survey comprised 3 main areas of enquiry: (a) exercise selection, (b) training protocols and organization, and (c) strongman event training. The back squat and conventional deadlift were reported as the most commonly used squat and deadlift (65.8 and 88.0%, respectively). Eighty percent of the subjects incorporated some form of periodization in their training. Seventy-four percent of subjects included hypertrophy training, 97% included maximal strength training, and 90% included power training in their training organization. The majority performed speed repetitions with submaximal loads in the squat and deadlift (59.9 and 61.1%, respectively). Fifty-four percent of subjects incorporated lower body plyometrics into their training, and 88% of the strongman competitors reported performing Olympic lifts as part of their strongman training. Seventy-eight percent of subjects reported that the clean was the most performed Olympic lift used in their training. Results revealed that 56 and 38% of the strongman competitors used elastic bands and chains in their training, respectively. The findings demonstrate that strongman competitors incorporate a variety of strength and conditioning practices that are focused on increasing muscular size, and the development of maximal strength and power into their conditioning preparation. The farmers walk, log press, and stones were the most commonly performed strongman exercises used in a general strongman training session by these athletes. These data provide information on the training practices required to compete in the sport of strongman.

A Review of Adolescent High-Intensity Interval Training

Despite the promising evidence supporting positive effects of high-intensity interval training (HIIT) on the metabolic profile in adults, there is limited research targeting adolescents. Given the rising burden of chronic disease, it is essential to implement strategies to improve the cardiometabolic health in adolescence, as this is a key stage in the development of healthy lifestyle behaviours. This narrative review summarises evidence of the relative efficacy of HIIT regarding the metabolic health of adolescents. Methodological inconsistencies confound our ability to draw conclusions; however, there is meaningful evidence supporting HIIT as a potentially efficacious exercise modality for use in the adolescent cohort. Future research must examine the effects of various HIIT protocols to determine the optimum strategy to deliver cardiometabolic health benefits. Researchers should explicitly show between-group differences for HIIT intervention and steady-state exercise or control groups, as the magnitude of difference between HIIT and other exercise modalities is of key interest to public health. There is scope for research to examine the palatability of HIIT as an exercise modality for adolescents through investigating perceived enjoyment during and after HIIT, and consequent long-term exercise adherence.

Anaerobic and aerobic fitness profiling of competitive surfers.

Abstract Farley, O, Harris, NK, and Kilding, AE. Anaerobic and aerobic fitness profiling of competitive surfers. J Strength Cond Res 26(8): 2243–2248, 2012—Despite widespread popularity of competitive surfing internationally, very little research has investigated the physiological profile of surf athletes and attempted to identify the relationships between physiological measures and surfing performance. This study determined the peak oxygen uptake (V[Combining Dot Above]O2peak) from an incremental ramp test and anaerobic power (watts) during a 10-second maximal-paddling burst using a surf paddle–specific modified kayak ergometer, customized with a surfboard and hand paddles. Twenty nationally ranked surf athletes volunteered to participate in the V[Combining Dot Above]O2peak test, and 8 also participated in the anaerobic power test. The interrelationships between these components of athletic performance and surfing performance, as assessed by season rank, were determined using Pearsons correlations. We found a significant relationship between anaerobic power and season rank (r = 0.55, p = 0.05). No significant relationship between V[Combining Dot Above]O2peak and season rank was found (r = −0.02, p = 0.97). Although correlations do not imply cause and effect, such a finding provides theoretical support for the importance of including anaerobic paddling power in assessment batteries and conditioning practice for surf athletes.