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Kraemer, WJ, Caldwell, LK, Post, EM, Volek, JS, Hagen, JM, Newton, RU, Häkkinen, K, Omonije, O, and Maresh, CM. Endogenous opioid peptides after floatation therapy in resistance trained men. J Strength Cond Res38(10): 1808–1812, 2024—Floatation-restricted environmental stimulation therapy (Float-REST) has shown improvements in muscle soreness and fatigue. To determine whether float influences the release of beta-endorphin (β-End) and proenkephalin (ProEnk) after acute heavy resistance exercise, 11 healthy resistance-trained men (age: 22.5 ± 2.3 years; height: 176.4 ± 6.0 cm; body mass: 85.7 ± 6.2 kg, back squat one-repetition maximum: 153.1 ± 20.1 kg; strength-to-mass ratio: 1.8 ± 0.2) completed a within-subject, cross-over controlled study design. Subjects completed 2 exercise testing blocks separated by a 2-week washout. In one block, a 1-hour float session followed the high-intensity resistance exercise protocol (6 × 10 back squats at 80% 1RM, 2 minutes rest). By contrast, recovery in the alternate block consisted of a passive sensory-stimulating control. Blood samples were collected at 5 time points—before exercise, immediately after exercise, after1-hour recovery treatment, 24 hours after exercise, and 48 hours after exercise. Samples were analyzed in duplicate for β-End and ProEnk using ELISA immunoassays. Mean differences were assessed using repeated-measures ANOVA. Plasma β-End demonstrated the expected significant (p≤ 0.05) increase following resistance exercise in both treatment conditions. There were no significant changes with exercise stress for ProEnk precursor peptide. The absence of significant differential changes following Float-REST suggests that these opioid peptides may not underlie the deep relaxation experiences commonly reported with this intervention in trained men. However, practically, it shows that β-End remains consistently similarly increased to high-intensity exercise stress. However, the ProEnk concentrations are detectable and stable but do not respond to the workout protocol, which, as a primary opioid peptide precursor, suggests paracrine cybernetics in the circulation may exist.

Kotikangas, J, Walker, S, Peltonen, H, and Häkkinen, K. Time course of neuromuscular fatigue during different resistance exercise loadings in power athletes, strength athletes, and nonathletes. J Strength Cond Res38(7): 1231–1242, 2024—Training background may affect the progression of fatigue and neuromuscular strategies to compensate for fatigue during resistance exercises. Thus, our aim was to examine how training background affects the time course of neuromuscular fatigue in response to different resistance exercises. Power athletes (PA, n= 8), strength athletes (SA, n= 8), and nonathletes (NA, n= 7) performed hypertrophic loading (HL, 5 × 10 × 10RM), maximal strength loadings (MSL, 7 × 3 × 3RM) and power loadings (PL, 7 × 6 × 50% of 1 repetition maximum) in back squat. Average power (AP), average velocity (VEL), surface electromyography (sEMG) amplitude (sEMGRMS), and sEMG mean power frequency (sEMGMPF) were measured within all loading sets. During PL, greater decreases in AP occurred from the beginning of SET1 to SET7 and in VEL to both SET4 and SET7 in NA compared with SA (p< 0.01, g> 1.84). During HL, there were various significant group × repetition interactions in AP within and between sets (p< 0.05, ηp2> 0.307), but post hoc tests did not indicate significant differences between the groups (p> 0.05, g= 0.01–0.93). During MSL and HL, significant within-set and between-set decreases occurred in AP (p< 0.001, ηp2> 0.701) and VEL (p< 0.001, ηp2> 0.748) concurrently with increases in sEMGRMS(p< 0.01, ηp2> 0.323) and decreases in sEMGMPF(p< 0.01, ηp2> 0.242) in all groups. In conclusion, SA showed fatigue resistance by maintaining higher AP and VEL throughout PL. During HL, PA tended to have the greatest initial fatigue response in AP, but between-group comparisons were nonsignificant despite large effect sizes (g> 0.8). The differences in the progression of neuromuscular fatigue may be related to differing neural activation strategies between the groups, but further research confirmation is required.

Seppänen, S and Häkkinen, K. Step vs. two-phase gradual volume reduction tapering protocols in strength training: Effects on neuromuscular performance and serum hormone concentrations. J Strength Cond Res36(10): 2771–2779, 2022—This study assessed effects of 2 reduced volume tapering protocols on neuromuscular performance and serum hormone concentrations in 14 recreationally strength-trained men (21–30 years). After an 8-week strength training period subjects were divided to the step (54% volume reduction immediately) and 2-phase gradual (38% reduction for the first week and 70% for the second week) tapering groups for 2 weeks. One repetition maximum (1RM) squat, maximal isometric bilateral leg press force (leg press MVIC), electromyography (EMG) of vastus lateralis (VL) and vastus medialis, cross-sectional area of VL, serum testosterone, cortisol, and sex hormone-binding globuline (SHBG) concentrations were measured before and repeatedly during training and tapering periods. Both tapering protocols led to significant increases (p< 0.01) in squat 1RM. However, the increase in the step group (3.4 ± 2.1%) was higher (p< 0.05) than in the gradual group (1.7 ± 0.9%). The maximal integrated EMG of VL increased (p< 0.05) during tapering in the step group. Serum testosterone concentration increased (p< 0.05) and T/SHBG ratio reached the highest level after 1-week tapering in the step group. In the gradual group, T/SHBG ratio was (p< 0.05) higher after the taper than after the training period. Individual changes in T/SHBG ratio in the total group correlated positively (p< 0.05) with individual changes in leg press MVIC during the taper. These results suggest that reducing training volume can be an effective way to peak maximal strength. However, a higher volume reduction rate at the beginning of taper seems to lead to more favorable changes in maximal strength accompanied by positive changes in the neuromuscular system and serum hormone concentrations when taper follows an overreaching period.

Kraemer, WJ, Caldwell, LK, Post, EM, Beeler, MK, Emerson, A, Volek, JS, Maresh, CM, Fogt, JS, Fogt, N, Häkkinen, K, Newton, RU, Lopez, P, Sanchez, BN, and Onate, JA. Arousal/stress effects of “Overwatch” eSports game competition in collegiate gamers. J Strength Cond Res36(10): 2671–2675, 2022—To date, no physical response data are available for one of the most popular eSport games, Overwatch. The purpose of this investigation was to describe the stress signaling associated with competitive Overwatchplay and to understand how acute hormonal responses may affect performance. Thirty-two male college-aged gamers (age: 21.3 ± 2.7 years; estimated time played per week: 18 ± 15 hours) completed the study. Subjects were randomly assigned to a 6-player team to compete in a tournament-style match. Salivary measures of cortisol and testosterone were collected immediately before (PRE) and after (POST) the first-round game, with the heart rate recorded continuously during the match. The mean characteristics were calculated for each variable and comparisons made by the skill level. Significance was defined as p≤ 0.05. There were no differences in measures of salivary cortisol. A differential response pattern was observed by the skill level for testosterone. The low skill group displayed a significant increase in testosterone with game play (mean ± SD, testosterone PRE: 418.3 ± 89.5 pmol·L−1, POST: 527.6 ± 132.4 pmol·L−1, p< 0.001), whereas no change was observed in the high skill group. There were no differences in heart rate characteristics between skill groups. Overall, the average heart rate was 107.2 ± 17.8 bpm with an average max heart rate of 133.3 ± 19.1 bpm. This study provides unique physiological evidence that a sedentary Overwatchmatch modulates endocrine and cardiovascular responses, with the skill level emerging as a potential modulator.

Supplemental Digital Content is Available in the Text.Pihlainen, K, Kyröläinen, H, Santtila, M, Ojanen, T, Raitanen, J, and Häkkinen, K. Effects of combined strength and endurance training on body composition, physical fitness, and serum hormones during a 6-month crisis management operation. J Strength Cond Res36(9): 2361–2370, 2022—Very few studies have examined the impact of training interventions on soldier readiness during an international military operation. Therefore, the present study investigated the effects of combined strength and endurance training on body composition, physical performance, and hormonal status during a 6-month international military deployment consisting of typical peacekeeping tasks, e.g., patrolling, observation, and on-base duties. Soldiers (n= 78) were randomly allocated to a control group (C) or one of 3 combined whole-body strength and endurance training groups with varying strength-to-endurance training emphasis (Es = 25/75%, SE= 50/50% or Se = 75/25% of strength/endurance training). Body composition, physical performance (3000-m run, standing long jump [SLJ], isometric maximal voluntary contraction of the lower [MVC lower] and upper extremities [MVC upper ], muscle endurance tests), and selected serum hormone concentrations were determined prior to training (PRE), and after 9 (MID) and 19 (POST) weeks of training. Within- and between-group changes were analyzed using linear regression models. The average combined strength and endurance training frequency of the total subject group was 3 ± 2 training sessions per week. No changes were observed in physical performance variables in the intervention groups, whereas SLJ decreased by 1.9% in C (p< 0.05). Maximal voluntary contraction lower increased by 12.8% in the combined intervention group (p< 0.05), and this was significantly different to C (p< 0.05). Testosterone-to-cortisol ratio increased in SEand Se (p< 0.05), whereas no change was observed in C. The intervention groups maintained or improved their physical performance during deployment, which is beneficial for operational readiness. However, the high interindividual variation observed in training adaptations highlights the importance of training individualization during prolonged military operations.

Previous studies have shown that military field training (MFT) has effects on warfighters' hormonal responses, neuromuscular performance, and shooting accuracy. The aim of the present study was to investigate the changes in body composition, upper and lower body strength, serum hormone concentrations of testosterone (TES) and cortisol (COR), insulin-like growth factor-1 (IGF-1), and sex hormone binding globulin (SHBG) and shooting accuracy during prolonged MFT.

Few studies have reported the amount of physical activity (PA) and its associations to physical performance of warfighters during military field training (MFT). The purpose of this study was to investigate changes in neuromuscular performance and PA among male Finnish Army conscripts during a 21-d MFT and to evaluate their recovery during 4 d after MFT.

Purpose To understand the systemic effect of major spine surgery, we investigated stress, anabolic and catabolic hormonal levels and their association with interleukin 6 (IL-6) in patients undergoing elective lumbar spine fusion surgery.Methods Blood samples were collected preoperatively, and at 1, 3, 42, 90 days postoperatively (POD) from 49 patients who underwent elective lumbar spine fusion surgery.Results Serum concentration of cortisol was below the preoperative value at POD 1 but did not differ from the baseline values thereafter. Adrenocorticotropic hormone (ACTH) decreased at PODs 1 and 3. Testosterone decreased at PODs 1 and 3 in men, and at POD 3 in women. Sex hormone-binding globulin decreased at PODs 1 and 3 in both genders. No changes were observed in free testosterone or growth hormone concentrations. Insulin-like growth factor 1 increased significantly above the preoperative level at PODs 42 and 90 in women, and at POD 42 in men. IL-6 was significantly elevated at PODs 1 and 3. Increases in IL-6 from the preoperative level to POD 1 correlated significantly with decreases of cortisol at POD 1 but not with ACTH.Conclusions There were only short-term stress hormonal changes after elective lumbar spine fusion surgery. Cortisol changes after elective lumbar spine surgery are transient and might be partly cytokine induced and non-ACTH driven since there was association between cortisol and IL-6 but not with ACTH and IL-6.

Purpose:The purpose of this study was to determine the effects of a multinutritional supplement including amino acids, β-hydroxy-β-methylbutyrate (HMB), and carbohydrates on cytokine responses to resistance exercise and training.Methods:Seventeen healthy, college-aged men were randomly assigned to a Muscle Armor™ (MA; Abbott Nutrition, Columbus, OH) or placebo supplement group and 12 weeks of resistance training. An acute resistance exercise protocol was administered at 0, 6, and 12 weeks of training. Venous blood samples at pre-, immediately post-, and 30-minutes postexercise were analyzed via bead multiplex immunoassay for 17 cytokines.Results:After 12 weeks of training, the MA group exhibited decreased interferon-gamma (IFN-γ) and interleukin (IL)-10. IL-1β differed by group at various times. Granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, IL-7, IL-8, IL-12p70, IL-13, IL-17, monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-1 beta (MIP-1β) changed over the 12-week training period but did not differ by group.Conclusions:Twelve weeks of resistance training alters the cytokine response to acute resistance exercise, and supplementation with HMB and amino acids appears to further augment this result.

Typical military tasks include load carriage, digging, and lifting loads. To avoid accumulation of fatigue, it is important to know the energy expenditure of soldiers during such tasks. The purpose of this study was to measure cardiorespiratory responses during military tasks in field conditions. Unloaded (M1) and loaded (M2) marching, artillery field preparation (AFP), and digging of defensive positions (D) were monitored. 15 conscripts carried additional weight of military outfit (5.4 kg) during M1, AFP, and D and during M2 full combat gear (24.4 kg). Absolute and relative oxygen uptake (VO2) and heart rate (HR) of M1 (n = 8) were 1.5 ± 0.1 L min(-1), 19.9 ± 2.7 mL kg(-1) min(-1) (42 ± 7% VO2max), and 107 ± 8 beats min(-1) (55 ± 3% HRmax), respectively. VO2 of M2 (n = 8) was 1.7 ± 0.2 L min(-1), 22.7 ± 3.4 mL kg(-1) min(-1) (47 ± 6% VO2max) and HR 123 ± 9 beats min(-1) (64 ± 4% HRmax). VO2 of AFP (n = 5) and D (n = 6) were 1.3 ± 0.3 L min(-1), 18.0 ± 3.0 (37 ± 6% VO2max), and 1.8 ± 0.4 L min(-1), 24.3 ± 5.1 mL kg(-1) min(-1) (51 ± 9% VO2max), respectively. Corresponding HR values were 99 ± 8 beats min(-1) (50 ± 3% HRmax) and 132 ± 10 beats min(-1) (68 ± 4% HRmax), respectively. The mean work intensity of soldiers was close to 50% of their maximal aerobic capacity, which has been suggested to be maximal limit of intensity for sustained work.

Predicted maximal oxygen uptake (VO2max) measurements are based on the assumption of linear relationship between heart rate or power output and oxygen consumption during various intensities. To develop more reliable predicted test for soldiers, the purpose of the present study was to compare the results of direct measurements of VO2max to respective predicted values in cycling (military fitness test). The predicted mean (+/- SD) peak oxygen uptake (VO2peak) value was 45.2 +/- 7.7 mL kg(-1) min(-1) during first week, whereas the respective direct value was 44.8 +/- 8.5 mL kg(-1) min(-1). During the ninth week, the predicted and measured mean (+/-SD) VO2max values were 47.4 +/- 6.7 mL kg(-1) min(-1) and 48.7 +/- 7.3 mL kg(-1) min(-1), respectively. The absolute differences between the methods were -0.42 mL kg(-1) min(-1) (p = 0.46) and 1.28 mL kg(-1) min(-1) (p < 0.05), which correspond to relative values of 0.9% and 2.7%, respectively. A Bland-Altman plot of measured VO2max and predicted VO2max showed no significant trend between the mean and the difference of the 2 methods either before (r = 0.14, p = 0.24) or after the basic military training period (r = 0.11, p = 0.36). Intraclass correlation coefficient varied between r = 0.82 to 0.94. In conclusion, the predicted protocol is fairly accurate (+/-3%) and reliable to predict VO2max values in male soldiers but the use for clinical purposes should be considered individually.

The purpose of the study was to examine the effects of an 8-week basic training (BT) with added strength training (ST) or endurance training (ET) on both the performance of a 3K-combat loaded run test and the acute neuromuscular and hormonal responses. All training groups improved (p < 0.001) their run-test times: ST by 12.4%, ET by 11.6%, and normal training (NT) by 10.2%. Significant acute decreases were observed in maximal isometric force of leg extensors (p < 0.01-0.05) in all subject groups following the run. Increases were observed in acute testosterone responses (p < 0.001) after the test in all groups both at pre- and post-training. However, ET and NT demonstrated lower (p < 0.001-0.05) acute post-training serum cortisol responses than ST. In conclusion, the present results indicate that within a demanding BT, the added training for ET and especially ST may be compromised in their adaptation potential due to interference from the demands of BT.

Introduction: Military personnel are often exposed to training programs and operational situations that involve multiple stressors such as caloric deficit, sleep deprivation, and prolonged physical effort, which may disturb body homeostasis, as indicated by hormonal responses. Therefore, we investigated the effects of three training regimens on serum basal hormone concentrations before and after the 8-wk basic training (BT) period, and whether possible changes in serum basal concentrations are related to changes in endurance and strength performance. Methods: Serum hormone levels were measured in 3 groups of 24 male military conscripts before and after 3 different types of training programs: normal basic training (NT); BT with added strength training (ST); and BT with added endurance training (ET). Results: ET and ST increased their maximal strength by 12.9% and glob, respectively, and their VO2max increased by 12.0% and 8.5%, but the changes did not differ significantly between the groups. Increases in serum basal testosterone concentration were observed in all groups (BT by 16.6%, ST by 16.3%, and ET by 26.6%). Serum basal cortisol concentration increased in ST by 11.1%. Serum basal thyroxine concentration decreased by 9.2% in NT, 11.9% in ST, and 10.5% in ET. Conclusions: The increases in strength, aerobic capacity, and testosterone after training indicate that the regimens were adequate to create positive training responses, especially in the ST and ET groups. On the other hand, unexpectedly low strength gains in the ST group during BT may be a consequence of too high an amount of endurance-based military training. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to examine the changes in cardiovascular performance (VO2 max) and maximal strength development during an 8-week basic training (BT) combined with emphasized endurance training (ET) or strength training (ST) among 72 conscripts. The emphasized ST and ET programs combined with BT improved VO2 max by 12.0% (p < 0.01) and 8.5% (p < 0.05), while the increase in the control group (normal training) was 13.4% (p < 0.001). Body fat and waist circumference decreased in all groups. Normal training did not increase maximal strength of leg extensors but both ST (9.1%; p < 0.05) and ET (12.9%; p < 0.01) did. In conclusion, the current BT program including a high amount of endurance training improved cardiovascular performance. However, no further improvements in VO2 max were obtained by added endurance training for three times a week. BT positively influenced body composition but BT alone was not a sufficient stimulus to increase the maximal strength of leg extensors.

The purpose of this research was to determine the effects of high intensity endurance training (ET) and resistance training (RT) alone and in combination on various military tasks. Thirty-five male soldiers were randomly assigned to one of four training groups: total body resistance training plus endurance training (RT + ET), upper body resistance training plus endurance training [UB + ET), RT only, and ET only. Training was performed 4 days per week for 12 weeks. Testing occurred before and after the 12-week training regimen. All groups significantly improved push-up performance, whereas only the RT + ET group did not improve sit-up performance. The groups that included ET significantly decreased 2-mile run time, however, only RT + ET and UB + ET showed improved loaded 2-mile run time. Leg power increased for groups that included lower body strengthening exercises (RT and RT + ET). Army Physical Fitness Test performance, loaded running, and leg power responded positively to training, however, it appears there is a high degree of specificity when concurrent training regimens are implemented.

KRAEMER, W. J., K. HÄKKINEN, N. T. TRIPLETT-MCBRIDE, A. C. FRY, L. P. KOZIRIS, N. A. RATAMESS, J. E. BAUER, J. S. VOLEK, T. MCCONNELL, R. U. NEWTON, S. E. GORDON, D. CUMMINGS, J. HAUTH, F. PULLO, J. M. LYNCH, S. A. MAZZETTI, and H. G. KNUTTGEN. Physiological Changes with Periodized Resistance Training in Women Tennis Players. Med. Sci. Sports Exerc., Vol. 35, No. 1, pp. 157–168, 2003.

NEWTON, R. U., K. HÄKKINEN, A. HÄKKINEN, M. MCCORMICK, J. VOLEK, and W. J. KRAEMER. Mixed-methods resistance training increases power and strength of young and older men. Med. Sci. Sports Exerc., Vol. 34, No. 8, pp. 1367–1375, 2002.

OBJECTIVE: To examine the effects of strength training on basal concentrations and acute responses of serum hormones, and their possible interrelationships with training induced muscle hypertrophy and strength gains of the knee extensor muscles in women with fibromyalgia (FM) and healthy controls. METHODS: Twenty-one premenopausal women with FM were randomized to 21 week strength training (FMT; n = 11) or control (FMC; n = 10) groups. Twelve premenopausal sedentary healthy women served as controls (HC). Surface electromyographic (EMG) activity, maximal unilateral isometric force of the right knee extensors, and muscle cross-sectional area (CSA) of the quadriceps femoris throughout the lengths of 3/12 to 12/15 of the femur (Lf) were measured. Serum concentrations of total and free testosterone and growth hormone (GH) were analyzed at rest and in pre- and post-exercise conditions, while levels of insulin-like growth factor and dehydroepiandrosterone sulfate were measured at rest only. RESULTS: Mean (SD) maximal force increased by 18% (10%) (p < 0.001) in the FMT group, and by 22% (12%) (p < 0.001) in the HC, while in the FMC it remained unchanged. Maximum integrated EMG of the agonists (VL + VM/2) increased in HC by 22% (p < 0.05) and in the FMT by 19% (p < 0.05). Significant increases in the CSA of the QF were observed at 5 to 12/15 Lf in FMT (p < 0.05-0.01) and at 3 to 12/15 Lf in HC (p < 0.05-0.001), while in FMC the CSA remained unchanged. No training induced changes occurred in the basal concentrations of serum hormones examined. A significant acute increase took place in the mean concentration of GH at pre-training in HC (p < 0.01) and in the FMT (p < 0.05), while at post-training the elevations after the loading (p < 0.001 and 0.05) remained elevated up to 15 min (p < 0.05) in HC and up to 30 min (p < 0.01) post-loading in the FMT. CONCLUSION: Both the magnitude and time course of adaptations of the neuromuscular system to resistance training in women with FM were completely comparable to those taking place in healthy women. Basal levels of the anabolic hormones seem to be similar in women with FM compared to age matched healthy women. Observations recorded during the acute loading conditions might be considered an indication of the training induced adaptation of the endocrine system, showing that the acute GH response may become systematic after strength training in both women with FM and controls.

IZQUIERDO, M., K. HÄKKINEN, A. ANTÓN, M. GARRUES, J. IBAÑEZ, M. RUESTA, and E. M. GOROSTIAGA. Maximal strength and power, endurance performance, and serum hormones in middle-aged and elderly men. Med. Sci. Sports Exerc., Vol. 33, No. 9, 2001, pp. 1577–1587.

Effects of strength training (ST) for 21 wk were examined in 10 older women (64 ± 3 yr). Electromyogram, maximal isometric force, one-repetition maximum strength, and rate of force development of the leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris (QF) and of vastus lateralis (VL), medialis (VM), intermedius (VI) and rectus femoris (RF) throughout the lengths of 3/12–12/15 (Lf) of the femur, muscle fiber proportion and areas of types I, IIa, and IIb of the VL were evaluated. Serum hormone concentrations of testosterone, growth hormone (GH), cortisol, and IGF-I were analyzed for the resting, preexercise, and postexercise conditions. After the 21-wk ST, maximal force increased by 37% (P< 0.001) and 1-RM by 29% (P< 0.001), accompanied by an increase (P< 0.01) in rate of force development. The integrated electromyograms of the vastus muscles increased (P< 0.05). The CSA of the total QF increased (P< 0.05) throughout the length of the femur by 5–9%. The increases were significant (P< 0.05) at 7/15–12/15 Lf for VL and at 3/15–8/15 Lf for VM, at 5/15–9/15 for VI and at 9/15 (P< 0.05) for RF. The fiber areas of type I (P< 0.05), IIa (P< 0.001), and IIb (P< 0.001) increased by 22–36%. No changes occurred during ST in serum basal concentrations of the hormones examined, but the level of testosterone correlated with the changes in the CSA of the QF (r= 0.64, P< 0.05). An acute increase of GH (P< 0.05), remaining elevated up to 30 min (P< 0.05) postloading, was observed only at posttraining. Both neural adaptations and the capacity of skeletal muscle to undergo training-induced hypertrophy even in older women explain the strength gains. The increases in the CSA of the QF occurred throughout its length but differed selectively between the individual muscles. The serum concentrations of hormones remained unaltered, but a low level of testosterone may be a limiting factor in training-induced muscle hypertrophy. The magnitude and time duration of the acute GH response may be important physiological indicators of anabolic adaptations during strength training even in older women.

KRAEMER, W. J., S. A. MAZZETTI, B. C. NINDL, L. A. GOTSHALK, J. S. VOLEK, J. A. BUSH, J. O. MARX, K. DOHI, A. L. GÓMEZ, M. MILES, S. J. FLECK, R. U. NEWTON, and K. HÄKKINEN. Effect of resistance training on women’s strength/power and occupational performances. Med. Sci. Sports Exerc., Vol. 33, No. 6, 2001, pp. 1011–1025.

MARX, J. O., N. A. RATAMESS, B. C. NINDL, L. A. GOTSHALK, J. S. VOLEK, K. DOHI, J. A. BUSH, A. L. GÓMEZ, S. A. MAZZETTI, S. J. FLECK, K. HÄKKINEN, R. U. NEWTON, and W. J. KRAEMER. Low-volume circuit versus high-volume periodized resistance training in women. Med. Sci. Sports Exerc., Vol. 33, No. 4, 2001, pp. 635–643.

KRAEMER, W. J., M. KEUNING, N. A. RATAMESS, J. S. VOLEK, M. McCORMICK, J. A. BUSH, B. C. NINDL, S. E. GORDON, S. A. MAZZETTI, R. U. NEWTON, A. L. GÓMEZ, R. B. WICKHAM, M. R. RUBIN, and K. HÄKKINEN. Resistance training combined with bench-step aerobics enhances women’s health profile. Med. Sci. Sports Exerc., Vol. 33, No. 2, pp. 259–269, 2001.

MAZZETTI, S. A., W. J. KRAEMER, J. S. VOLEK, N. D. DUNCAN, N. A. RATAMESS, A. L. GÓMEZ, R. U. NEWTON, K. HÄKKINEN, and S. J. FLECK. The influence of direct supervision of resistance training on strength performance. Med. Sci. Sports Exerc.,Vol. 32, No. 6, pp. 1175–1184, 2000.

To examine the adaptations of the endocrine system to heavy-resistance training in younger vs. older men, two groups of men (30 and 62 yr old) participated in a 10-wk periodized strength-power training program. Blood was obtained before, immediately after, and 5, 15, and 30 min after exercise at rest before and after training and at rest at −3, 0, 6, and 10 wk for analysis of total testosterone, free testosterone, cortisol, growth hormone, lactate, and ACTH analysis. Resting values for insulin-like growth factor (IGF)-I and IGF-binding protein-3 were determined before and after training. A heavy-resistance exercise test was used to evaluate the exercise-induced responses (4 sets of 10-repetition maximum squats with 90 s of rest between sets). Squat strength and thigh muscle cross-sectional area increased for both groups. The younger group demonstrated higher total and free testosterone and IGF-I than the older men, training-induced increases in free testosterone at rest and with exercise, and increases in resting IGF-binding protein-3. With training the older group demonstrated a significant increase in total testosterone in response to exercise stress along with significant decreases in resting cortisol. These data indicate that older men do respond with an enhanced hormonal profile in the early phase of a resistance training program, but the response is different from that of younger men.

Influence of exercise training on physiological and performance changes with weight loss in men. Med. Sci. Sports Exerc.,Vol. 31, No. 9, pp. 1320-1329, 1999.

The responses of serum myocellular proteins and hormones to exercise were studied in ten well-trained middle-distance runners [maximal oxygen consumption ( V?O 2max)?=?69.4?(5.1)?ml?·?kg -1?·?min -1] during 3 recovery days and compared to various measures of physical performance. The purpose was to establish the duration of recovery from typical intermittent middle-distance running exercises. The subjects performed, in random, order two 28-min treadmill running exercises at a velocity associated with V?O 2max: 14 bouts of 60-s runs with 60?s of rest between each run (IR 60) and 7 bouts of 120-s runs with 120?s of rest between each run (IR 120). Before the exercises (pre- exercise), 2?h after, and 1, 2 and 3 days after the exercises, the same series of measurements were performed, including those for serum levels of the myocellular proteins creatine kinase, myoglobin and carbonic anhydrase III (S-CK, S-Mb and S-CA III, respectively), serum hormones testosterone, Luteinizing hormone, follicle-stimulating hormone and cortisol (S-testosterone, S-LH, S-FSH and S-cortisol, respectively) and various performance parameters: maximal vertical jump height (CMJ) and stride length, heart rate and ratings of perceived exertion during an 8-min run at 15?km?·?h -1 (SL 15?km·h-1, HR 15?km?·?h-1 and RPE 15?km?·?h-1, respectively). Two hours after the end of both exercise bouts the concentration of each measured serum protein had increased significantly ( P?15?km?·?h-1 or CMJ. During the recovery days only S-CK was significantly raised ( P?15?km?·?h-1 ( P?120 the post-exercise responses returned to their pre-exercise levels within the 3 days of recovery. The present findings suggest that a single 28-min intermittent middle-distance running exercise does not induce changes in serum hormones of well-trained runners during recovery over 3 days, while changes in S-CK, CMJ and RPE 15?km?·?h-1 indicate that 2–3 days of light training may be needed before the recovery at muscle level is complete.

To investigate the effects of simultaneous explosive-strength and endurance training on physical performance characteristics, 10 experimental (E) and 8 control (C) endurance athletes trained for 9 wk. The total training volume was kept the same in both groups, but 32% of training in E and 3% in C was replaced by explosive-type strength training. A 5-km time trial (5K), running economy (RE), maximal 20-m speed (V20 m), and 5-jump (5J) tests were measured on a track. Maximal anaerobic (MART) and aerobic treadmill running tests were used to determine maximal velocity in the MART (VMART) and maximal oxygen uptake (V˙o2 max). The 5K time, RE, andVMARTimproved (P< 0.05) in E, but no changes were observed in C.V20 mand 5J increased in E (P< 0.01) and decreased in C (P< 0.05).V˙o2 maxincreased in C (P< 0.05), but no changes were observed in E. In the pooled data, the changes in the 5K velocity during 9 wk of training correlated (P< 0.05) with the changes in RE [O2uptake (r= −0.54)] andVMART(r= 0.55). In conclusion, the present simultaneous explosive-strength and endurance training improved the 5K time in well-trained endurance athletes without changes in theirV˙o2 max. This improvement was due to improved neuromuscular characteristics that were transferred into improvedVMARTand running economy.

To investigate the effects of a combination of simultaneous strength and endurance training on selected neuromuscular and aerobic performance characteristics seven male cross-country skiers underwent training for a period of 6 weeks. The experimental group trained 6–9 times per week with a programme consisting of 34% explosive type strength training and 66% endurance training during the first 3 weeks of the experiment and 42% and 58% respectively during the last 3 weeks of the experiment. The total volume of training of the control group (eight skiers) was of the same magnitude but consisted of 85% pure endurance training and 15% endurance type strength training. The experimental training regime resulted in specific changes in neuromuscular performance. This was demonstrated by improvements (P<0.01) in the maximal heights of rise of the centre of gravity in the squat and countermovement jumps. A significant decrease (P<0.05) took place also in the time of rapid isometric force production during experimental training, while no changes occurred in the maximal force of the trained muscles. Aerobic performance characteristics of the experimental group did not change during the experimental training period. No significant changes occurred in neuromuscular or aerobic performance characteristics in the control group. These findings indicated that training-induced improvements in explosive force production may not be fully inhibited by this kind of aerobic training. They also suggested that endurance athletes could undertake explosive type strength training programmes without a concomitant reduction in aerobic capacity, if the overall loading of training were within predefined limits.

The effects of a 1 year training period on 13 elite weight-lifters were investigated by periodical tests of electromyographic, muscle fibre and force production characteristics. A statistically non-significant increase of 3.5% in maximal isometric strength of the leg extensors, from 4841±1104 to 5010±1012 N, occured over the year. Individual changes in the high force portions of the force-velocity curve correlated (p<0.05–0.01) with changes in weight-lifting performance. Training months 5–8 were characterized by the lowest average training intensity (77.1+2.0%), and this resulted in a significant (p<0.05) decrease in maximal neural activation (IEMG) of the muscles, while the last four month period, with only a slightly higher average training intensity (79.1±3.0%), led to a significant (p<0.01) increase in maximum IEMG. Individual increases in training intensity between these two training periods correlated with individual increases both in muscular strength (p<0.05) and in the weight lifted in the clean & jerk (p<0.05). A non-significant increase of 3.9% in total mean muscle fibre area occurred over the year. The present findings demonstrate the limited potential for strength development in elite strength athletes, and suggest that the magnitudes and time courses of neural and hypertrophic adaptations in the neuromuscular system during their training may differ from those reported for previously untrained subjects. The findings additionally indicate the importance of training intensity for modifying training responses in elite strength athletes.

Effects of fatigue produced by a maintained 60% isometric loading on electromyographic and isometric force-time and relaxation-time characteristics of human skeletal muscle were studied in 21 males accustomed to strength training. Fatigue loading resulted in a slight but not significant change in the maximal integrated EMG of a maximal isometric contraction, and a large decrease (20.4±6.3%, p<0.001) in maximal force. Fatigue loading increased (p<0.05-0.01) neural activation of the muscles during rapidly produced submaximal isometric forces, but had a considerable adverse effect (p<0.001) on the corresponding force-time characteristics. Correlations between the relative changes after fatigue in the IEMG/force ratio at the maximal force level, and in the IEMG/force ratios of the early phases of the force-time curve were not significant, but gradually became significant (p<0.01) at higher force levels. The average IEMG of the muscles in the relaxation phase of contraction remained unaltered by fatigue, while a marked deleterious change in the relaxation-time variables (p<0.001) occurred concomitantly. During the subsequent 3 min rest period considerable (12.1±7.0%, p<0.001) recovery was noted in the maximal force, with smaller (insignificant or p<0.05-0.01) changes in the force-time and relaxation-time variables, while the average IEMG of force production decreased (p<0.01-0.001). The present findings suggest that fatigue leading to a worsening in force-time, in maximal force and in the relaxation-time parts of a maximal isometric contraction might take place primarily in the contractile processes.

To investigate the influence of strength training on the mechanical characteristics of human skeletal muscle, 14 male subjects went through training of combined heavy concentric and eccentric contractions three times a week for 16 weeks. The strength training program consisted mainly of dynamic exercises for leg extensors with loads of 80 to 120% of one maximum repetition. The force-time curves produced during various vertical jumps were the basis for calculation of various mechanical parameters. In addition to a great increase (p<0.001) in maximal isometric force, heavy resistance strength training also caused significant (p<0.05-0.01) increases in heights and in various mechanical parameters in positive work phases of vertical and drop jumps. The increase in positive force during a fast dynamic contraction was correlated (p<0.01) with the reduced time to produce a certain submaximal force level in isometric condition. No changes in the elastic properties of the muscle were observed as judged from the difference between the counter-movement and squat jumps. When the training was followed by the 8-week detraining period a great decrease (p<0.001) in maximal force took place, but only minor changes (ns) were observed in fast force production.

The purpose of this study was to investigate neuromuscular and energy performance characteristics of anaerobic power and capacity and the development of fatigue. Ten endurance and ten sprint athletes performed a new maximal anaerobic running power test (MARP), which consisted ofn x 20-s runs on a treadmill with 100-s recovery between the runs. Blood lactate concentration [la−]b was measured after each run to determine submaximal and maximal indices of anaerobic power (P3mmol·1−1,P5mmol·1−1,P10mmol·1−1andPmax) which was expressed as the oxygen demand of the runs according to the American College of Sports Medicine equation: the oxygen uptake (ml·kg−1·min−1)=0.2·velocity (m·min−1) +0.9·slope of treadmill (frac)·velocity (m·min−1)+3.5. The height of rise of the centre of gravity of the counter movement jumps before (CMJrest) and during (CMJ) the MARP test, as well as the time of force production (tF) and electromyographic (EMG) activity of the leg muscles of CMJ performed after each run were used to describe the neuromuscular performance characteristics. The maximal oxygen uptake ( max), anaerobic and aerobic thresholds were determined in the max test, which consisted ofn x 3-min runs on the treadmill. In the MARP-testPmax did not differ significantly between the endurance [116 (SD 6) ml·kg−1·min−1] and sprint [120 (SD 4) ml·kg−1·min−1] groups, even though CMJrest and peak [la−]b were significantly higher and max was significantly lower in the sprint group than in the endurance group and CMJrest height correlated withPmax (r=0.50,P<0.05). The endurance athletes had significantly higher mean values ofP3mmol·1−1andP5mmol·1−1[89 (SD 7) vs 76 (SD 8) ml·kg−1·min−,P<0.001 and 101 (SD 5) vs 90 (SD 8) ml·kg−1·min−1,P<0.01. Significant positive correlations were observed between theP3mmol·l−1and max, anaerobic and aerobic thresholds. In the sprint group CMJ and the averaged integrated iEMG decreased andtF increased significantly during the MARP test, while no significant changes occurred in the endurance group. The present findings would suggest thatPmax reflected in the main the lactacid power and capacity and to a smaller extent alactacid power and capacity. The duration of the MARP test and the large number of CMJ may have induced considerable energy and neuromuscular fatigue in the sprint athletes preventing them from producing their highest alactacidPmax at the end of the MARP test. Due to lower submaximal [la−]b (anaerobic sprinting economy) the endurance athletes were able to reach almost the samePmax as the sprint athletes.

To investigate training-induced changes in neuromuscular performance under voluntary and reflex contractions, 11 male subjects went through heavy resistance (high loads of 70–120% of one maximum repetition) and 10 male subjects through explosive type (low loads with high contraction velocities) strength training three times a week for 24 weeks. A large increase (13.9%,p<0.01) in voluntary unilateral maximal knee extension strength with only slight and insignificant changes in time of isometric force production were observed during heavy resistance strength training. Explosive type strength training resulted in a small insignificant increase in maximal strength but in considerable shortening (p<0.05) in the time of force production. A significant increase (p<0.05) noted in the averaged maximal integrated electromyogram (IEMG) of the knee extensors during heavy resistance strength training correlated (p<0.01) with the increase in maximal strength. No changes were noted during training in reflex time components, but significant decreases (p<0.05) occurred in the peak-to-peak amplitudes of the reflex electromyograms (EMG) in both groups. The individual changes during training in the reflex EMG/force ratio were related (p<0.01) to the respective changes in IEMG/force ratio in voluntary contractions. The present observations support the concept of specificity of training, and suggest that specific training-induced adaptations in the neuromuscular system may be responsible for these changes in performance.

The effects of progressive strength training for 24 weeks on maximal strength and pituitary-thyroid function were studied in 21 males during the training and during the following detraining period of 12 weeks. Maximal strength increased greatly (p<0.001) in the first 20 weeks, followed by a plateau phase in the last 4 weeks of training. Maximal strength decreased greatly (p<0.001) during the detraining period. The concentrations of serum total (T4) and free thyroxine (fT4) decreased (p<0.05 and <0.01, respectively) during the training period and they rose to pretraining levels during the detraining period. During the most intense training phase (the last 4 weeks) there was a positive correlation between the changes in serum fT4 concentrations and the changes in maximal force (r=0.56; p<0.01). No statistically significant changes occurred in the levels of serum triiodothyronine, thyrotropin or thyroxine binding gobulin. The results show that prolonged intensified strength training can slightly decrease the concentrations of serum total and free T4. These small changes cannot have any clinical significance, and even their physiological significance may be only marginal.

The effects of a 24-weeks' progressive training of neuromuscular performance capacity on maximal strength and on hormone balance were investigated periodically in 21 male subjects during the course of the training and during a subsequent detraining period of 12 weeks. Great increases in maximal strength were noted during the first 20 weeks, followed by a plateau phase during the last 4 weeks of training. Testosterone/cortisol ratio increased during training. During the last 4 weeks of training changes in maximal strength correlated with the changes in testosterone/cortisol (P<0.01) and testosterone/SHBG (P<0.05) ratios. During detraining, correlative decreases were found between maximal strength and testosterone/cortisol ratio (P<0.05) as well as between the maximal strength and testosterone/SHBG ratio (P<0.05). No statistically significant changes were observed in the levels of serum estradiol, lutropin (LH), follitropin (FSH), prolactin, and somatotropin. The results suggest the importance of the balance between androgenic-anabolic activity and catabolizing effects of glucocorticoids during the course of vigorous strength training.

Effects of ballistic training on preseason preparation of elite volleyball players. Med. Sci. Sports Exerc.,Vol. 31, No. 2, pp. 323-330, 1999.

This investigation examined hormonal adaptations to acute resistance exercise and determined whether training adaptations are observed within an 8-week period in untrained men and women. The protocol consisted of a 1-week pre-conditioning orientation phase followed by 8 weeks of heavy resistance training. Three lower-limb exercises for the quadriceps femoris muscle group (squat, leg press, knee extension) were performed twice a week (Monday and Friday) with every other Wednesday used for maximal dynamic 1 RM strength testing. Blood samples were obtained pre-exercise (Pre-Ex), immediately post-exercise (IP), and 5?min post-exercise (5-P) during the first week of training (T-1), after 6 weeks (T-2) and 8 weeks (T-3) of training to determine blood concentrations of whole-blood lactate (LAC), serum total testosterone (TT), sex-hormone binding globulin (SHBG), cortisol (CORT) and growth hormone (GH). Serum TT concentrations were significantly ( P?=?0.05) higher for men at all time points measured. Men did not demonstrate an increase due to exercise until T-2. An increase in pre-exercise concentrations of TT were observed both for men and women at T-2 and T-3. No differences were observed for CORT between men and women; increases in CORT above pre-exercise values were observed for men at all training phases and at T-2 and T-3 for women. A reduction in CORT concentrations at rest was observed both in men and women at T-3. Women demonstrated higher pre-exercise GH values than men at all training phases; no changes with training were observed for GH concentrations. Exercise-induced increases in GH above pre-exercise values were observed at all phases of training. Women demonstrated higher serum concentrations of SHBG at all time points. No exercise-induced increases were observed in men over the training period but women increased SHBG with exercise at T-3. SHBG concentrations in women were also significantly higher at T-2 and T-3 when compared to T-1 values. Increases in LAC concentrations due to exercise were observed both for men and women for all training phases but no significant differences were observed with training. These data illustrate that untrained individuals may exhibit early-phase endocrine adaptations during a resistance training program. These hormonal adaptations may influence and help to mediate other adaptations in the nervous system and muscle fibers, which have been shown to be very responsive in the early phase of strength adaptations with resistance training.

The purpose of this investigation was to examine the acute responses of several hormones [total and free testosterone (TT and FT, respectively), adrenocorticotropic hormone (ACTH), cortisol (C), growth hormone (GH), and insulin (INS)] to a single bout of heavy resistance exercise (HRE). Eight younger [30-year (30y) group] and nine older [62-year (62y) group] men matched for general physical characteristics and activity levels performed four sets of ten repetitions maximum (RM) squats with 90?s rest between sets. Blood samples were obtained from each subject via an indwelling cannula with a saline lock pre-exercise, immediately post-exercise (IP), and 5, 15 and 30?min post-exercise. Levels of TT, FT, ACTH, C and lactate significantly increased after HRE for both groups. Pre-HRE pairwise differences between groups were noted only for FT, while post-HRE pairwise differences were found for TT, FT, GH, glucose and lactate. Area under the curve analysis showed that the 30y group had a significantly higher magnitude of increase over the entire recovery period (IP, 5, 15, and 30?min post-exercise) for TT, FT, ACTH and GH. Few changes occurred in the INS response with the only change being that the 62y group demonstrated a decrease IP. Lactate remained elevated at 30?min post-HRE. This investigation demonstrates that age-related differences occur in the endocrine response to HRE, and the most striking changes appear evident in the FT response to HRE in physically active young and older men.

Although explosive power in lower-body movements has been extensively studied, there is a paucity of research examining such movements in the upper body. This study aimed to investigate the influence of load and the stretch shortening cycle (SSC) on the kinematics, kinetics, and muscle activation that occurs during maximal effort throws. A total of 17 male subjects performed SSC and concentric only (CO) bench throws using loads of 15%, 30%, 45%, 60%, 75%, 90% and 100% of their previously determined one repetition maximum bench press. The displacement, velocity, acceleration, force and power output as well as the electromyogram (EMG) from pectoralis major, anterior deltoid, and triceps brachii were recorded for each throw. The results were compared using multivariate analysis of variance with repeated measures. A criterion alpha level of P?=?0.05 was used. Similar force velocity power relationships were determined for this multijoint upper-body movement as has been found for isolated muscles, single joint movements, and vertical jumping. The highest power output was produced at the 30% [563 (104) W] and 45% [560 (86) W] loads during the SSC throws. Force output increased as a function of load; however, even the lighter loads resulted in considerable force due to the high accelerations produced. Average velocity, average and peak force, and average and peak power output were significantly higher for the SSC throws compared to the CO throws. However, peak velocity and height thrown were not potentiated by performing the pre-stretch because the duration and range of movement allowed the ability of the muscle to generate force at high shortening velocities to dominate the resulting throw. As such, explosive movements involving longer concentric actions than experienced during brief SSC movements may be limited by the ability of the muscle to produce force during fast contraction velocities.

Purpose: Interleukin 6 (IL-6) and the acute phase C-reactive protein (CRP) blood concentrations after lumbar spine fusion may be affected by age. The purpose of this prospective observational study was to assess postoperative serum levels of pro-inflammatory IL-6 and CRP after instrumented lumbar spine fusion surgery. We hypothesized that older patients would have increased levels of IL-6 and CRP after surgery.Methods: IL-6 and high-sensitive CRP biochemical marker levels were measured before instrumented spinal fusion, and postoperatively at 1 and 3 days, 6 weeks, and 3 months. The 49 patients in this sample were divided into two groups: age ≤ 60 years (n= 23) and age > 60 years (n= 26).Results: Acute changes in IL-6 high-sensitivity and CRP from preoperative levels to postoperative day (POD) 1 increased with age. Mean (95% CI) difference between the age-groups in changes of IL-6 at PODs 1 and 3 was 45 pg/ml (10–83, p= 0.014) and 20 pg/ml (5–36, p= 0.021), respectively. Mean (95% CI) difference between groups in changes of CRP at PODs 1 and 3 was 9.6 mg/l (−3.5 to 22.7, p= 0.47) and 24.8 mg/l (−17 to 67, p= 0.33), respectively. Both groups had decreased IL-6 and CRP levels at 6 weeks after surgery compared to the preoperative level.Conclusions: Elevation of IL-6 and CRP is stronger in patients over 60 years old after instrumented lumbar spinal fusion. The CRP and IL-6 are sensitive markers for acute postoperative inflammation. Even high acute CRP values do not necessarily indicate postoperative infection.