Isoload vs isokinetic eccentric exercise: a direct comparison of exercise-induced muscle damage and repeated bout effect

Downhill running increases markers of muscle damage and impairs the maximal voluntary force production as well as the late phase of the rate of voluntary force development

PURPOSE

To examined the time-course of the early and late phase of the rate of voluntary force development (RVFD) and muscle damage markers after downhill running.

METHODS

Ten recreational runners performed a 30-min downhill run at 10 km h-1 and -20% (-11.3°) on a motorized treadmill. At baseline and each day up to 4 days RVFD, knee extensors maximum voluntary isometric force (MVIC), serum creatine kinase (CK) concentration, quadriceps swelling, and soreness were assessed. The early (0-50 ms) and late (100-200 ms) phase of the RVFD, as well as the force developed at 50 and 200 ms, were also determined.

RESULTS

MVIC showed moderate decrements (p < 0.05) and recovered after 4 days (p > 0.05). Force at 50 ms and the early phase were not impaired (p > 0.05). Conversely, force at 200 ms and the late phase showed moderate decrements (p < 0.05) and recovered after 3 and 4 days, respectively (p > 0.05). CK concentration, quadriceps swelling, and soreness increased (p < 0.05) were overall fully resolved after 4 days (p > 0.05).

CONCLUSION

Downhill running affected the knee extensors RVFD late but not early phase. The RVFD late phase may be used as an additional marker of muscle damage in trail running.

High-Density Electromyography Excitation in Front vs. Back Lat Pull-Down Prime Movers

The current study compared the spatial excitation of the primary muscles during the lat pull-down exercise with the bar passing in front (front-LPD) or behind the neck (back-LPD) using high-density electromyography. Fourteen resistance trained men performed a front-LPD or a back-LPD within a non-fatiguing set with 8-RM as the external load. The muscle excitation centroid of latissimus dorsi, middle trapezius, pectoralis major, biceps brachii, triceps brachii and posterior deltoid muscles were recorded during the ascending and the descending phase. During the descending phase, the front-LPD showed superior excitation of the latissimus dorsi (ES = 0.97) and the pectoralis major (ES = 1.17), while in the ascending phase, the back-LPD exhibited superior excitation of the latissimus dorsi (ES = 0.63), and the front-LPD showed superior excitation of the biceps brachii (ES = 0.41) and the posterior deltoid (ES = 1.77). During the descending phase, the front-LPD showed a more lateral centroid of the latissimus dorsi (ES = 0.60), the biceps brachii (ES = 0.63) and the triceps brachii (ES = 0.98), while the centroid was more medial for the middle trapezius (ES = 0.58). The centroid of the middle trapezius was also more medial in the front-LPD during the ascending phase (ES = 0.85). The pectoralis major centroid was more cranial in the front-LPD for both the descending (ES = 1.58) and the ascending phase (ES = 0.88). The front-LPD appears to provide overall greater excitation in the prime movers. However, distinct spatial excitation patterns were observed, making exercise suitable for the training routine.

Biceps Brachii and Brachioradialis Excitation in Biceps Curl Exercise: Different Handgrips, Different Synergy

The current study analyzed the excitation of biceps brachii, brachioradialis, and anterior deltoid during bilateral biceps curl performed with different handgrips. Ten competitive bodybuilders performed bilateral biceps curl in non-exhaustive 6-rep sets using 8-RM with the forearm in supinated, pronated, and neutral positions. The ascending and descending phase of each variation was separately analyzed using the normalized root mean square collected using surface electromyography. During the ascending phase, (i) biceps brachii excitation was greater with the supinated compared to the pronated [+19(7)%, ES: 2.60] and neutral handgrip [+12(9)%, ES: 1.24], (ii) the brachioradialis showed greater excitation with the supinated compared to the pronated [+5(4)%, ES: 1.01] and neutral handgrip [+6(5)%, ES: 1.10], (iii) the anterior deltoid excitation was greater with the pronated and neutral handgrip compared to the supinated condition [+6(3)% and +9(2)%, ES: 2.07 and 3.18, respectively]. During the descending phase, the anterior deltoid showed greater excitation in the pronated compared to the supinated handgrip [+5(4)%, ES: 1.02]. Changing the handgrips when performing biceps curl induces specific variations in biceps brachii and brachioradialis excitation and requires different anterior deltoid interventions for stabilizing the humeral head. Practitioners should consider including different handgrips in the biceps curl routine to vary the neural and mechanical stimuli.

Bilateral Biceps Curl Shows Distinct Biceps Brachii and Anterior Deltoid Excitation Comparing Straight vs. EZ Barbell Coupled with Arms Flexion/No-Flexion

The present study investigated the excitation of the biceps brachii and anterior deltoid during bilateral biceps curl performed using the straight vs. EZ barbell and with or without flexing the arms. Ten competitive bodybuilders performed bilateral biceps curl in non-exhaustive 6-rep sets using 8-RM in four variations: using the straight barbell flexing (ST_flex) or not flexing the arms (ST_no-flex) or the EZ barbell flexing (EZ_flex) or not flexing the arms (EZ_no-flex). The ascending and descending phases were separately analyzed using the normalized root mean square (nRMS) collected using surface electro-myography. For the biceps brachii, during the ascending phase, a greater nRMS was observed in ST_no-flex vs. EZ_no-flex (+1.8%, effect size [ES]: 0.74), in ST_flex vs. ST_no-flex (+17.7%, ES: 3.93) and in EZ_flex vs. EZ_no-flex (+20.3%, ES: 5.87). During the descending phase, a greater nRMS was observed in ST_flex vs. EZ_flex (+3.8%, ES: 1.15), in ST_no-flex vs. ST_flex (+2.8%, ES: 0.86) and in EZ_no-flex vs. EZ_flex (+8.1%, ES: 1.81). The anterior deltoid showed distinct excitation based on the arm flexion/no-flexion. A slight advantage in biceps brachii excitation appears when using the straight vs. EZ barbell. Flexing or not flexing the arms seems to uniquely excite the biceps brachii and anterior deltoid. Practitioners should consider including different bilateral biceps barbell curls in their routine to vary the neural and mechanical stimuli.

Including the Eccentric Phase in Resistance Training to Counteract the Effects of Detraining in Women: A Randomized Controlled Trial

ABSTRACT

Coratella, G, Beato, M, Bertinato, L, Milanese, C, Venturelli, M, and Schena, F. Including the eccentric phase in resistance training to counteract the effects of detraining in women: a randomized controlled trial. J Strength Cond Res 36(11): 3023-3031, 2022-The current study compared the effects of concentric-based (CONC), eccentric-based (ECC), and traditional concentric-eccentric (TRAD) resistance training on muscle strength, mass, and architecture and the postdetraining retention of the training-induced effects in women. Sixty women were randomly assigned to unilateral volume-equated CONC, ECC, or TRAD knee extension training or control ( N = 15 per group). Before training, after an 8-week intervention period, and after an 8-week detraining period, isokinetic concentric, eccentric, and isometric torque were measured. In addition, thigh lean mass was assessed by dual X-ray absorptiometry and vastus lateralis thickness, pennation angle, and fascicle length by ultrasound. After training, concentric and isometric torque increased ( p < 0.05) similarly in all groups, whereas eccentric torque increased more in ECC than that in CONC (+13.1%, effect size (ES): 0.71 [0.04-1.38]) and TRAD (+12.6%, ES: 0.60 [0.12-1.08]). Thigh lean mass increased in ECC (+6.1%, ES: 0.47 [0.27-0.67]) and TRAD (+3.1%, ES: 0.33 [0.01-0.65]). Vastus lateralis thickness and pennation angle increased ( p < 0.05) similarly in all groups, whereas fascicle elongation was visible in ECC (+9.7%, ES: 0.92 [0.14-1.65]) and TRAD (+7.1%, ES: 0.64 [0.03-1.25]). After detraining, all groups retained ( p < 0.05) similar concentric torque. ECC and TRAD preserved eccentric torque ( p < 0.05), but ECC more than TRAD (+17.9%, ES: 0.61 [0.21-1.21]). All groups preserved isometric torque ( p < 0.05), but ECC more than CONC (+14.2%, ES: 0.71 [0.04-1.38]) and TRAD (+13.8%, ES: 0.65 [0.10-1.20]). Thigh lean mass and vastus lateralis fascicle length were retained only in ECC ( p < 0.05), pennation angle was preserved in all groups ( p < 0.05), and thickness was retained in CONC and ECC ( p < 0.05). Including the eccentric phase in resistance training is essential to preserve adaptations after detraining.

Appropriate Reporting of Exercise Variables in Resistance Training Protocols: Much more than Load and Number of Repetitions

Manipulating resistance training variables is crucial to plan the induced stimuli correctly. When reporting the exercise variables in resistance training protocols, sports scientists and practitioners often refer to the load lifted and the total number of repetitions. The present conceptual review explores all within-exercise variables that may influence the strength and hypertrophic gains, and the changes in muscle architecture. Together with the (1) load and (2) the number of repetitions, (3) performing repetitions to failure or not to failure, (4) the displacement of the load or the range of movement (full or partial), (5) the portion of the partial movement to identify the muscle length at which the exercise is performed, (6) the total time under tension, the duration of each phase and the position of the two isometric phases, (7) whether the concentric, eccentric or concentric-eccentric phase is performed, (8) the use of internal or external focus and (9) the inter-set rest may all have repercussions on the adaptations induced by each resistance exercise. Manipulating one or more variable allows to increase, equalize or decrease the stimuli related to each exercise. Sports scientists and practitioners are invited to list all aforementioned variables for each exercise when reporting resistance training protocols.

Front vs Back and Barbell vs Machine Overhead Press: An Electromyographic Analysis and Implications For Resistance Training

Overhead press is commonly performed to reinforce the muscles surrounding the shoulders. However, many overhead press variations can be executed, thus varying the stimuli to each muscle. Therefore, the current study compared the muscles excitation during overhead press performed with the barbell passing in front or behind the head or using a shoulder press machine. Eight competitive bodybuilders performed in random order front (front-BMP) or back barbell military press (back-BMP), and front (front-MSP) with neutral handgrip or back machine shoulder press (back-MSP). Normalized surface electromyographic root mean square (RMS) of anterior, medial and posterior deltoid, upper trapezius, pectoralis major and triceps brachii was recorded during both the ascending and descending phases. During the ascending phase, anterior deltoid showed greater RMS in back-BMP than back-MSP [ES: 1.42, (95% confidence interval 0.32/2.51)]. Medial deltoid showed greater RMS in back-BMP than front-BMP [ES: 3.68 (2.07/5.29)], and back-MSP [ES: 7.51 (4.73/10.29)]. Posterior deltoid showed greater RMS in back-BMP than front-BMP [ES: 9.00 (5.73/12.27)]. Pectoralis major showed greater RMS in front-BMP than back-BMP [ES: 3.11 (1.65–4.56)] and in front-MSP than back-MSP [ES: 20.52 (13.34/27.70)]. During the descending phase, anterior deltoid was more excited in back-BMP compared to front-BMP [ES: 7.66 (4.83/10.49). Medial deltoid showed greater RMS in back-BMP than front-BMP [ES: 4.56 (2.70/6.42)]. Posterior deltoid showed greater RMS in back-BMP than front-BMP [ES: 8.65 (5.50/11.80)]. Pectoralis major showed greater RMS in front-BMP than back-BMP [ES: 4.20 (2.44/5.95)]. No between-exercise difference was observed for upper trapezius. Performing back overhead press enhances the excitation of medial and posterior and partly anterior deltoid, while front overhead favors pectoralis major. Overhead press performed using barbell excites muscles more than using machine to stabilize the trajectory of the external load. Different variations of overhead press appear to provide different stimuli to the shoulder muscles and may be used accordingly during the training routine.

The Effects of Verbal Instructions on Lower Limb Muscles' Excitation in Back-Squat

The present study investigated whether or not verbal instruction affects the electromyographic (EMG) amplitude of back-squat prime movers. Fifteen resistance-trained men performed back-squat at 50%1-RM and 80%1-RM and received external (EF) or internal focus (IF) on lower-limb posterior muscles. EMG amplitude of gluteus maximus, biceps femoris, gastrocnemius medialis, vastus lateralis, and tibialis anterior was recorded during both concentric and eccentric phases. During the concentric phase, the gluteus maximus and biceps femoris EMG amplitude was greater in IF vs EF at 50% [effect size (ES): 0.63 (95%CI 0.09/1.17) and 0.49 (0.10/0.78), respectively] and 80% [ES: 1.30 (0.29/2.21) and 0.59 (0.08/1.10)]. The gastrocnemius medialis EMG amplitude was greater in IF vs EF during the eccentric phase at 50% [ES: 0.73 (0.13/1.33)] and at 80% [ES: 0.72 (0.10/1.34)]. Concomitantly, vastus lateralis EMG amplitude was lower at 50% [ES: -0.71 (-1.38/-0.04)] and 80% [ES: -0.68 (-1.33/-0.03)]. During the eccentric phase, the tibialis anterior EMG amplitude was greater in IF vs EF at 50% [ES: 0.90 (0.12 to 1.68)] and 80% [ES: 0.74 (0.13/1.45)]. Irrespective of the load, in the thigh muscles the internal focus promoted a different motor pattern, increasing the hip extensors and reducing the knee extensor excitation during the concentric phase. Concomitantly, both ankle muscles were more excited during the eccentric phase, possibly to increase the anterior-posterior balance control. The internal focus in back-squat seems to have phase-dependent effects, and it is visible at both moderate and high loads.

The Eccentric Phase in Unilateral Resistance Training Enhances and Preserves the Contralateral Knee Extensors Strength Gains After Detraining in Women: A Randomized Controlled Trial

The current randomized controlled study investigated whether or not the inclusion of the eccentric phase in resistance training favors the contralateral strength gains after different unilateral protocols, and whether such gains are retained after detraining. Sixty healthy women were randomly assigned to a unilateral concentric-only (CONC), eccentric-only (ECC), concentric–eccentric (TRAD) volume-equated knee extension training or control group (CON). The participants trained 2 days/week for 8 weeks and then did not train for further 8 weeks. Knee extensors isokinetic concentric, eccentric, and isometric peak torque and vastus lateralis muscle thickness were assessed in the contralateral limb at baseline, post-training, and post-detraining. At post-training, concentric peak torque increased in CONC [+9.2%, 95%CI (+6.2/+12.3), p < 0.001, ES: 0.70, 95%CI (0.01/1.39)], ECC [+11.0% (+7.7/+14.2), p < 0.001: ES: 0.66(0.09/1.23)] and TRAD [+8.5%(+5.7/+11.6), p < 0.001, ES: 0.50(0.02/0.98)]. Eccentric peak torque increased in ECC in ECC [+15.0%(+11.4/+20.7), p < 0.001, ES: 0.91(0.14/1.63)] and TRAD [+5.5%(+0.3/10.7), p = 0.013, ES: 0.50(0.05/0.95)]. Isometric peak torque increased in ECC [+11.3(+5.8/16.8), p < 0.001, ES: 0.52(0.10/0.94)] and TRAD [+8.6%(+3.4/+13.7), p < 0.001, ES: 0.55(0.14/0.96)]. No change in eccentric and isometric peak torque occurred in CONC (p > 0.05). Muscle thickness did not change in any group (p > 0.05). At post-detraining, all groups preserved the contralateral strength gains observed at post-training (p < 0.05). The findings showed that ECC and TRAD increased contralateral knee extensors strength in concentric, eccentric, and isometric modality, while CONC only increased concentric strength. The eccentric phase appears to amplify the cross-education effect, permitting a transfer in strength gaining toward multiple testing modalities. Both eccentric-based and traditional eccentric–concentric resistance protocols are recommended to increase the contralateral retention in strength gains after a detraining period.

An Electromyographic Analysis of Romanian, Step-Romanian, and Stiff-Leg Deadlift: Implication for Resistance Training

The present study examined the posterior chain muscle excitation in different deadlift variations. Ten competitive bodybuilders (training seniority of 10.6 ± 1.8 years) performed the Romanian (RD), Romanian standing on a step (step-RD), and stiff-leg deadlift (SD) with an 80% 1-RM. The excitation of the gluteus maximus, gluteus medius, biceps femoris, semitendinosus, erector spinae longissimus, and iliocostalis was assessed during both the ascending and descending phases. During the ascending phase, the RMS of the gluteus maximus was greater in the step-RD than in the RD (effect size (ES): 1.70, 0.55/2.84) and SD (ES: 1.18, 0.11/2.24). Moreover, a greater RMS was found in the SD than in the RD (ES: 0.99, 0.04/1.95). The RMS of the semitendinosus was greater in the step-RD than in the RD (ES: 0.82, 0.20/1.44) and SD (ES: 3.13, 1.67/4.59). Moreover, a greater RMS was found in the RD than in the SD (ES: 1.38, 0.29/2.48). The RMS of the longissimus was greater in the step-RD than in the RD (ES: 2.12, 0.89/3.34) and SD (ES: 3.28, 1.78/4.78). The descending phase had fewer differences between the exercises. No further differences between the exercises were found. The step-RD increased the overall excitation of the posterior chain muscles, possibly because of the greater range of movement and posterior muscle elongation during the anterior flexion. Moreover, the RD appeared to target the semitendinosus more than the SD, while the latter excited the gluteus maximus more.

Effect of Exercise-Induced Muscle Damage on Bowling-Specific Motor Skills in Male Adolescent Cricketers

The current study examined the acute effects of a bout of resistance training on cricket bowling-specific motor performance. Eight sub-elite, resistance-untrained, adolescent male fast bowlers (age 15 ± 1.7 years; height 1.8 ± 0.1 m; weight 67.9 ± 7.9 kg) completed a bout of upper and lower body resistance exercises. Indirect markers of muscle damage (creatine kinase [CK] and delayed onset of muscle soreness [DOMS]), anaerobic performance (15-m sprint and vertical jump), and cricket-specific motor performance (ball speed, run-up time, and accuracy) were measured prior to and 24 (T24) and 48 (T48) hours following the resistance training bout. The resistance training bout significantly increased CK (~350%; effect size [ES] = 1.89-2.24), DOMS (~240%; ES = 1.46-3.77) and 15-m sprint times (~4.0%; ES = 1.33-1.47), whilst significantly reducing vertical jump height (~7.0%; ES = 0.76-0.96) for up to 48 h. The ball speed (~3.0%; ES = 0.50-0.61) and bowling accuracy (~79%; ES = 0.39-0.70) were significantly reduced, whilst run-up time was significantly increased (~3.5%; ES = 0.36-0.50) for up to 24 h. These findings demonstrate that a bout of resistance training evokes exercise-induced muscle damage amongst sub-elite, adolescent male cricketers, which impairs anaerobic performance and bowling-specific motor performance measures. Cricket coaches should be cautious of incorporating bowling sessions within 24-h following a bout of resistance training for sub-elite adolescent fast bowlers, particularly for those commencing a resistance training program.

The Activation of Gluteal, Thigh, and Lower Back Muscles in Different Squat Variations Performed by Competitive Bodybuilders: Implications for Resistance Training

The present study investigated the activation of gluteal, thigh, and lower back muscles in different squat variations. Ten male competitive bodybuilders perform back-squat at full (full-BS) or parallel (parallel-BS) depth, using large feet-stance (sumo-BS), and enhancing the feet external rotation (external-rotated-sumo-BS) and front-squat (FS) at 80% 1-RM. The normalized surface electromyographic root-mean-square (sEMG RMS) amplitude of gluteus maximus, gluteus medius, rectus femoris, vastus lateralis, vastus medialis, adductor longus, longissimus, and iliocostalis was recorded during both the ascending and descending phase of each exercise. During the descending phase, greater sEMG RMS amplitude of gluteus maximus and gluteus medius was found in FS vs. all other exercises (p < 0.05). Additionally, FS elicited iliocostalis more than all other exercises. During the ascending phase, both sumo-BS and external-rotated-sumo-BS showed greater vastus lateralis and adductor longus activation compared to all other exercises (p < 0.05). Moreover, rectus femoris activation was greater in FS compared to full-BS (p < 0.05). No between-exercise difference was found in vastus medialis and longissimus showed no between-exercise difference. FS needs more backward stabilization during the descending phase. Larger feet-stance increases thigh muscles activity, possibly because of their longer length. These findings show how bodybuilders uniquely recruit muscles when performing different squat variations.

An Electromyographic Analysis of Lateral Raise Variations and Frontal Raise in Competitive Bodybuilders

The present study examined the muscle activation in lateral raise with humerus rotated externally (LR-external), neutrally (LR-neutral), internally (LR-internal), with flexed elbow (LR-flexed) and frontal raise during both the concentric and eccentric phase. Ten competitive bodybuilders performed the exercises. Normalized surface electromyographic root mean square (sEMG RMS) was obtained from anterior, medial, and posterior deltoid, pectoralis major, upper trapezius, and triceps brachii. During the concentric phase, anterior deltoid and posterior deltoid showed greater sEMG RMS in frontal raise (effect size (ES)-range: 1.78/9.25)) and LR-internal (ES-range: 10.79/21.34), respectively, vs. all other exercises. Medial deltoid showed greater sEMG RMS in LR-neutral than LR-external (ES: 1.47 (95% confidence-interval—CI: 0.43/2.38)), frontal raise (ES: 10.28(95% CI: 6.67/13.01)), and LR-flexed (ES: 6.41(95% CI: 4.04/8.23)). Pectoralis major showed greater sEMG RMS in frontal raise vs. all other exercises (ES-range: 17.2/29.5), while upper trapezius (ES-range: 2.66/7.18) and triceps brachii (ES-range: 0.41/3.31) showed greater sEMG RMS in LR-internal vs. all other exercises. Similar recruitment patterns were found during the eccentric phase. When humerus rotates internally, greater activation of posterior deltoid, triceps brachii, and upper trapezius occurs. Humerus external rotation increases the activation of anterior and medial deltoid. Frontal raise mainly activates anterior deltoid and pectoralis major. LR variations and frontal raise activate specifically shoulders muscles and should be proposed accordingly.

Sex-Related Responses to Eccentric-Only Resistance Training in Knee-Extensors Muscle Strength and Architecture

PURPOSE

The present study aimed to investigate whether or not eccentric-only training induced different sex-related adaptations in vastus lateralis muscle architecture and knee extensors strength.

METHODS

Thirteen healthy women and 13 healthy men were recruited. Vastus lateralis pennation angle, fascicle length, and muscle thickness, as well as knee extensors eccentric, isometric, and concentric peak torque and one-repetition maximum (1RM) were measured. Both women and men underwent a unilateral iso-load knee-extension eccentric-only training with 120% of the concentric 1RM, consisting of 4 sets × 10 repetitions twice a week for a total of 8 weeks.

RESULTS

Pennation angle increased in women (+ 14%, 95% CI [10, 17], effect size [ES] = 1.54) but not in men (+ 5%, 95% CI [-1, 11], ES = 0.28), while fascicle length increased in both women (+ 7%, 95% CI [4, 10], ES = 1.02) and men (+ 12%, 95% CI [8, 16], ES = 1.82) and muscle thickness increased in women (+ 13%, 95% CI [8, 18], ES = 1.11) and men (+ 11%, 95% CI [7, 15], ES = 0.89). In both women and men, eccentric (18%, 95% CI [11, 25], ES = 0.96, and 16%, 95% CI [9, 22], ES = 0.82, respectively), isometric (17%, 95% CI [11, 23], ES = 0.53, and 17%, 95% CI [10, 24], ES = 0.62), concentric (12%, 95% CI [7, 16], ES = 0.49, and 9%, 95% CI [5, 13], ES = 0.42) peak torque and 1RM (10%, 95% CI [6, 14], ES = 0.53, and 10%, 95% CI [5, 15], ES = 0.50) similarly increased after the intervention.

CONCLUSIONS

This study showed that the adaptations in strength are not sex-dependent, but the increases in pennation angle only in women suggest that the changes in muscle architecture may depend on sex.

Quadriceps concentric-eccentric force and muscle architecture in COPD patients vs healthy men

The aim of this study was to compare quadriceps concentric and eccentric strength and muscle architecture in chronic obstructive pulmonary disease (COPD) patients vs healthy men. Thirty-five COPD patients (age = 65 ± 4 yrs, forced expiratory volume (FEV₁) = 63 ± 10%; FEV₁/forced vital capacity (FVC)=57 ± 13% of predicted) and 25 age-matched healthy men (age = 65 ± 4 yrs, FEV₁=114 ± 17%; FEV₁/FVC = 101 ± 6% of predicted) (CON) participated in the present cross-sectional study. Concentric and eccentric isokinetic peak-torque was measured at low and high angular-velocity. Vastus lateralis pennation angle, fascicle length and muscle thickness were recorded using ultrasound device. Similar eccentric peak-torque was found in COPD and CON at low (2.57 ± 0.55 and 2.80 ± 0.60 N⋅m⋅kg^-1, p = 0.128 respectively) and high (2.44 ± 0.51 and 2.58 ± 0.46 N⋅m⋅kg^-1, p = 0.259) angular-velocity. Lower concentric peak-torque was found in COPD than in CON (p < 0.05). Smaller pennation angle (13.8 ± 3.4 vs 16.2 ± 3.9°) and muscle thickness (17.1 ± 2.8 vs 20.3 ± 3.0 mm) were found in COPD patients vs healthy men, with no difference in fascicle length. In COPD patients only, FEV₁ and FEV₁/FVC were negatively correlated with the eccentric-to-concentric peak-torque ratio (r = -0.465 and r = -0.414, respectively); irrespective of the testing-modality, FEV₁ and FEV₁/FVC were moderately correlated with peak-torque (p < 0.05). The preserved eccentric strength in COPD patients could be accounted for both mechanical and neural adaptations caused by the disease severity.

Correlation between quadriceps and hamstrings inter-limb strength asymmetry with change of direction and sprint in U21 elite soccer-players

The aim of this study was to investigate the relationship between in quadriceps and hamstrings inter-limb strength asymmetry and change of direction, sprinting and jumping abilities in U21 elite soccer players. Twenty-seven soccer players volunteered for this study. Isokinetic quadriceps and hamstrings peak torque was measured at high and low angular velocities, both in concentric and eccentric modalities. Performance in agility T-test, 20 + 20 m shuttle-test, 10 m and 30 m sprint, squat jump (SJ) and counter-movement jump (CMJ), were measured. Overall, time on agility T-test and 20 + 20 m shuttle-test was moderately and positively correlated with the quadriceps and hamstrings inter-limb eccentric peak torque asymmetry, both at high and low angular velocities. In addition, time on 10 m and 30 m sprints was moderately and positively correlated with the hamstrings inter-limb high-velocity concentric peak torque asymmetry. SJ and CMJ showed trivial to small correlations with hamstrings and quadriceps inter-limb peak torque asymmetry. The present results provide further information insight the role of lower-limb muscle strength balance in COD, sprinting and jumping performance.

Different training responses to eccentric endurance exercise at low and moderate altitudes in pre-diabetic men: a pilot study

This pilot study aimed (a) to evaluate the effects of eccentric exercise training at low and moderate altitudes on physical fitness in pre-diabetic men and (b) to establish whether or not oxidative stress levels and antioxidant status were associated with performance improvements. In this crossover trial, five pre-diabetic men conducted nine downhill walking sessions (3 days/week, 3 consecutive weeks) at low altitude (from 1360 to 850 m) and one year later at moderate altitude (from 2447 to 2000 m). Exercise testing and the determination of parameters of oxidative stress and antioxidant capacity were performed pre- and post-training. The biological antioxidant activity of plasma (BAP) increased after eccentric training at moderate altitude (p < 0.001), whereas diacron reactive oxygen metabolites (dROMs) remained unchanged. Also, the BAP/dROMs ratio increased only after training at moderate-altitude training (p = 0.009). Maximum power output improved after training at low altitude and the changes were significantly related to baseline BAP/dROMs ratio (r = 0.90). No decrease was seen for fasting plasma glucose. Eccentric exercise training in pre-diabetic men improved performance only when performed at low altitude and this improvement was positively related to the baseline BAP/dROMs ratio. In contrast, 3 weeks of eccentric exercise training increased BAP levels and the BAP/dROMs ratio only at moderate altitude without improving the performance. Thus, one might speculate that the BAP/dROMs ratio has to increase before performance improvements occur at moderate altitude.

Eccentric resistance training increases and retains maximal strength, muscle endurance, and hypertrophy in trained men

The aim of the present study was to evaluate the effects of different resistance training protocols on muscle strength, endurance, and hypertrophy after training and detraining. Thirty-four resistance-trained males were randomized in concentric-only (CONC), eccentric-only (ECC), traditional concentric-eccentric (TRAD) bench press resistance training or control group. The training volume was equalized among the intervention groups. Bench press of 1-repetition maximum (1RM)/body mass, maximum number of repetitions (MNR), and chest circumference were evaluated at the baseline, after 6 weeks of training, and after 6 weeks of detraining. All intervention groups reported significant 1RM/body mass increases after training (CONC baseline: 1.04 ± 0.06, post-training: 1.12 ± 0.08, p < 0.05; ECC baseline: 1.08 ± 0.04, post-training: 1.15 ± 0.05, p < 0.05; TRAD baseline: 1.06 ± 0.08, post-training: 1.11 ± 0.10, p < 0.05). After detraining, only ECC retained 1RM/body mass above the baseline (1.17 ± 0.07, p < 0.05), while CONC and TRAD returned to baseline values. Only ECC improved and retained MNR (baseline: 22 ± 3; post-training: 25 ± 3, and post-detraining: 25 ± 4, p < 0.05 compared with baseline) and chest circumference (baseline: 98.3 ± 2.4 cm, post-training: 101.7 ± 2.2 cm and post-detraining: 100.7 ± 2.3 cm. p < 0.05 compared with baseline), while no significant changes occurred in both CONC and TRAD. The incorporation of eccentric training can be recommended for counteracting the negative effects of detraining or forced physical inactivity.