Adaptations and acute physiological effects of various resistance training programs in adolescent and elite athletes

Introduction: The ability to perform typical athletic movements such as running and jumping is strongly linked with performance outcomes in many sports. Resistance training has been associated with improving these qualities and is commonly used by elite athletes to aid sports performance. Through the careful manipulation of resistance training programs and associated variables, a range of program types can be used by athletes to improve strength and power. As such, the effect of maximum strength or maximum power training programs on sports performance are of great interest. To effectively assess this impact on performance, various body composition, morphological and neuromuscular tests have been utilised. The overall aim of this thesis was to examine the responses, both chronic and acute, of athletes to maximum strength and maximum power training during various preparation and in-season periods. Subsequently, a series of studies were conducted to examine the effects of maximum strength and/or maximum power training on performance in various athlete subgroups during their normal preparation and competition periods. In the first study (Chapter 4), the effects of an in-season vs preparation period resistance training program on body composition, muscle morphology and neuromuscular adaptations were investigated in adolescent athletes. The second study (Chapter 5), extended this research, examining the acute neuromuscular effects and recovery profile of adolescent athletes to a fatiguing maximum strength training session at three different periods during their annual training. Study 3 (Chapter 6) examined the use of both a bodyweight countermovement jump CMJ(BW) and a loaded countermovement jump CMJ(LOAD) as longitudinal, neuromuscular readiness monitoring tools. The fourth study (Chapter 7) compared the effect of both a maximum strength and maximum power training program on the lower body power of endurance and strength/power athletes. The final study (Chapter 8) examined the effects of an in-season strength/power program on lower body power in elite team sport athletes. Methods: In Chapter 4, 14 adolescent male athletes performed a nine week in-season maximum strength training program and a six-week, preparation period maximum strength training program. Body composition, morphological and neuromuscular assessments were also conducted before and after both training periods to assess changes over each period. For Chapter 5, the same 14 adolescent athletes performed a fatiguing maximum strength training session consisting of ten sets of five repetitions of back squat at 85% 1RM at various time points throughout the year, i.e. early pre-season (block 1), post a competition period (block 2) and post a six-week maximum strength training preparation period (block 3). To assess the acute neuromuscular effects and recovery profile, a testing battery comprising a countermovement jump (CMJ), drop jump (DJ), isometric mid-thigh pull (IMTP) and 20 m sprint was performed before as well as immediately, 4, 24s, and 48 h post the training session. Chapter 6 assessed an elite male adult beach volleyball athlete for neuromuscular readiness using a CMJ(BW) and a CMJ(LOAD) over a 23-week period. In Chapter 7, five elite endurance athletes (rowers) and five elite strength/power athletes performed a four-week maximum strength program and a four-week maximum power program during a preparation period. To assess the impact of these programs on performance, the athletes were tested using a CMJ(BW) and a CMJ(LOAD) (30% 1RM back squat) every week across the training periods. For Chapter 8, the same assessment tools were used as in Chapter 7 however this time the subjects were elite Australian rules football players (n=46) who were assessed in-season. Results: In Chapter 4, the preparation period maximum strength training block resulted in a very likely small beneficial change in vastus lateralis thickness and 3RM back squat strength and possibly small beneficial changes in multiple CMJ variables. No real effects were observed in any other tests. During the in-season block, likely small beneficial changes in 20-m sprint variables where observed with no other effects found. For Chapter 5, DJ performance showed the greatest fatigue susceptibility following the maximum strength training stimulus with moderate harmful effects on jump height observed immediately post strength training for block 1 and block 2 and 24 h and 48 h post block 1. CMJ also showed fatigue susceptibility, however not to the same extent as the DJ. The IMTP showed a fatigue effect only immediately post the strength training session, whereas the 20-m sprint only showed a fatigue effect after strength training at the end of a competition period. Conversely, the 20-m sprint showed a performance potentiation effect when testing was performed after the athletes had completed a strength training block. In Chapter 6, relative peak power appeared the most accurate measure of training induced neuromuscular fatigue, varying appropriately in relation to training load for both a CMJ(BW) and CMJ(LOAD). Chapter 7 showed that strength/power athletes exhibited greater increases in relative peak power than endurance athletes after the maximum strength block for both the CMJ(BW) (7.8% ± 4.8%) and CMJ(LOAD) (5.9% ± 8.3%). After the maximum power block the strength/power athletes showed greater increases compared with endurance athletes both relative peak power and jump height when measured via a CMJ(BW) (9.8% ± 8.6% and 8.0% ± 6.4% respectively) and a CMJ(LOAD) (7.0% ± 5.7% and 5.2% ± 4.6% respectively). Chapter 8 found that, CMJ(BW) and CMJ(LOAD), showed similar abilities to detect varying levels of neuromuscular readiness. Performance variables such as relative peak power and jump height showed the most similar patterns of fatigue whilst the technique variable, centre of gravity movement, showed less similarity in the fatigue response. Conclusion: Adolescent athletes who perform a minimum six-week maximum strength training block will experience improvements in muscle pennation angle, lower body strength (3RM back squat) and CMJ performance whilst a competition block utilising more speed training is likely to see improvements in 20-m sprint time as highlighted by the findings of Chapter 4. Results from Chapter 5 suggest that the DJ is more effected by acute fatigue from a maximum strength training session than either the CMJ, IMTP or 20-m sprint whilst stronger athletes may be less susceptible to the fatigue generated by this type of training. Chapter 6 suggests that the CMJ(BW) is an appropriate test to monitor the weekly neuromuscular fatigue generated via an athletes' combined training load. Strength/power athletes are likely to see greater gains in CMJ(BW) and CMJ(LOAD) variables such as relative peak power and jump height when compared with endurance athletes when both groups perform either a maximum strength or maximum power four-week training block as shown by the results from Chapter 7. Chapter 8 highlights that a CMJ(BW) and CMJ(LOAD) show very similar results when tracking the weekly, in-season neuromuscular readiness of elite Australian rules football players with both output and technical execution variables showing similar results. In summary, strength and power variables as assessed via the above tests show clear but specific effects across, different athlete groups. Specifically, adolescent athletes showed clear adaptations to a six-week maximum strength block and a clear acute response to single maximum strength session. Additionally, strength/power athletes showed a larger performance benefit from both strength and power training compared with endurance athletes. In monitoring performance, the CMJ and associated variables was consistently a valid measure of performance changes over a training cycle and a valid measure of acute neuromuscular readiness. Practical applications: Maximum-strength and -power training cause different athletic performance changes due to the underpinning effects on muscle and neural physiology. Simple neuromuscular performance tests may be appropriate for assessing these changes, negating the need for invasive or time consuming laboratory based assessments. These effects are also relevant to the type of athlete performing the training program and can result in the following training effects: 1. Adolescents: a. A six-week maximum strength training program has beneficial impacts on muscle morphology and multiple neuromuscular performance variables. b. Maximum strength training has the largest fatigue effect on DJ performance and less effect on IMTP performance. c. Adolescent athletes may be better equipped to deal with the neuromuscular fatigue associated with a maximum strength training session as detected by CMJ, DJ, IMTP and 20 m sprint after performing a six-week strength block. 2. Adult individual sports: a. The CMJ(BW) appears more effective to monitor longitudinal neuromuscular fatigue generated by total training load in a Beach Volleyball athlete than the CMJ(LOAD) when a taper is included in the monitoring period. b. Strength/power athletes show better performance benefits when compared with endurance athletes in both the CMJ(BW) and CMJ(LOAD) after four-week maximum-strength and -power training blocks performed during their normal pre-season. 3. Adult team sports: a. CMJ(BW) and CMJ(LOAD) show similar neuromuscular fatigue responses to the demands of, weekly competition of elite AFL athletes.