Adaptive cognitive tasks for mental fatigue: An innovative paradigm for cognitive loading in human performance.

OBJECTIVES: Mental fatigue (MF) can impair cognitive and physical performance in sport. We tested the hypothesis that a shorter adaptive Time Load Dual Back (TLDB) task induces MF faster than a longer Stroop; and subsequently impairs cognitive and intermittent running performance. DESIGN: This study employed a randomized within-participant design. METHODS: 25 trained individuals performed a Yo-Yo test after one of four experimental conditions (30-min Stroop, 20-min and 10-min TLDB tasks, and active control). Cognitive performance was assessed using the Psychomotor Vigilance Task (PVT) before and after the experimental conditions. Measures of mood, workload, MF, RPE, heart rate (HR), heart rate variability (HRV) and blood lactate were collected. ANOVAs determined the effect of the 4 conditions. RESULTS: Stroop and 20-min TLDB conditions impaired running performance similarly (p = .015), while no differences are reported for 10-min TLDB and Control. No significant differences in physiological parameters were reported during the Yo-Yo test although RPE was significantly higher in the Stroop and 20-min TLDB conditions (p = .014). Stroop and both TLDBs conditions impaired PVT's cognitive performance (p = .029), MF (p = .012), mental demand (p < .001), HR (p = .021) and HRV (p = .033); with 20-min TLDB task having the higher significant impact. Mood alterations were similar between Stroop and TLDB conditions. CONCLUSIONS: Intermittent running (Yo-Yo) and cognitive (PVT) performances, and subjective ratings were impaired by 30-min Stroop and 20-min TLDB tasks; while 10-min TLDB did not to impair performance. Shorter adaptive modes seem to be more effective in inducing MF and could have relevant clinical applications to assess conditions such as traumatic brain injury and concussion.

Concurrent validation of the resistance intensity scale for exercise for monitoring velocity-based training with elastic bands.

The aim was to evaluate the concurrent validity and reliability of the Resistance Intensity Scale for Exercise [RISE], which uses verbal descriptors, to quantify the intensity in velocity-based training with elastic bands. Eighteen trained volunteers performed parallel squats at maximum speed at 40%, 55%, 70%, and 85%1RM in four sessions, two for familiarization and two for reliability. Each set was stopped at a 10% intra-set velocity loss. Participants reported the perceived effort (easy-low-moderate-hard-maximal) at the first and last repetition. The concurrent validation was conducted with external load (i.e., mean propulsive velocity, weight, repetitions, and maximum power) and internal load parameters (i.e., heart rate). Participants' relative strength was calculated to assess its influence on the dependent variable. Acceptable concurrent validity and reliability (ICC>0.77, CV<21%) were observed, with the perceived effort being appropriate to differentiate between intensities and not being influenced by the participants' relative strength (p = 0.88). A categorical linear regression showed significant (p < 0.001) associations between the RISE scores and the weight, repetitions, and mean propulsive velocity (r = 0.43-0.63). The findings certify the usefulness of the perceived exertion for quantifying the intensity during velocity-based training with elastic bands. The perceived exertion of the first and last repetition favors a proper dosage of the training load.

A new sports garment with elastomeric technology optimizes physiological, mechanical, and psychological acute responses to pushing upper-limb resistance exercises.

This study aimed to compare the mechanical (lifting velocity and maximum number of repetitions), physiological (muscular activation, lactate, heart rate, and blood pressure), and psychological (rating of perceived exertion) responses to upper-body pushing exercises performed wearing a sports elastomeric garment or a placebo garment. Nineteen physically active young adults randomly completed two training sessions that differed only in the sports garment used (elastomeric technology or placebo). In each session, subjects performed one set of seated shoulder presses and another set of push-ups until muscular failure. The dependent variables were measured immediately after finishing the set of each exercise. Compared to the placebo garment, the elastomeric garment allowed participants to obtain greater muscular activation in the pectoralis major (push-ups: p = 0.04, d = 0.49; seated shoulder press: p < 0.01, d = 0.64), triceps brachialis (push-ups, p < 0.01, d = 0.77; seated shoulder press: p < 0.01, d = 0.65), and anterior deltoid (push-ups: p < 0.01, d = 0.72; seated shoulder press: p < 0.01, d = 0.83) muscles. Similarly, participants performed more repetitions (push-ups: p < 0.01; d = 0.94; seated shoulder press: p = 0.03, d = 0.23), with higher movement velocity (all p ≤ 0.04, all d ≥ 0.47), and lower perceived exertion in the first repetition (push-ups: p < 0.01, d = 0.61; seated shoulder press: p = 0.05; d = 0.76) wearing the elastomeric garment compared to placebo. There were no between-garment differences in most cardiovascular variables (all p ≥ 0.10). Higher diastolic blood pressure was only found after the seated shoulder press wearing the elastomeric garment compared to the placebo (p = 0.04; d = 0.49). Finally, significantly lower blood lactate levels were achieved in the push-ups performed wearing the elastomeric garment (p < 0.01; d = 0.91), but no significant differences were observed in the seated shoulder press (p = 0.08). Overall, the findings of this study suggest that elastomeric technology integrated into a sports garment provides an ergogenic effect on mechanical, physiological, and psychological variables during the execution of pushing upper-limb resistance exercises.

Barefoot vs shod walking and jogging on the electromyographic activity of the medial and lateral gastrocnemius.

Gastrocnemius weakness is associated with Achilles tendinopathies and muscle strains, with the medial gastrocnemius (MG) more commonly injured than the lateral gastrocnemius (LG). Walking and jogging are common in daily activities and sports, and biomechanical differences between shod and barefoot exercise may influence MG and LG activation. Understanding these activation patterns could help optimize training programs for injury prevention and/or rehabilitation. The aim was to compare MG and LG electromyographic activity during walking and jogging, both shod and barefoot. Twenty-nine participants (25.28 ± 4.53 years, 171.31 ± 0.76 cm, 72.68 ± 6.36 kg) completed a warm-up followed by 1 min of walking (80-99 steps/min) and jogging (130-150 steps/min) in both conditions (barefoot and shod, random order). Electromyographic signals were recorded using wearable devices (mDurance Solutions S.L., Granada, Spain; 1024 Hz sampling rate). We measured the root-mean-square (RMS) amplitudes for an entire stride cycle and digitally filtered the signals. For analysis, we normalized electromyographic values to the average peak values obtained during two sprints. We analyzed differences with a repeated-measures analysis of variance. Significant effects of condition (barefoot-shod) and gastrocnemius (MG-LG) were observed (all p ≤ 0.023, ƞp2 = 0.17-0.39), with higher MG activation compared to LG in the barefoot conditions (p = 0.004-0.027, d = 0.72-0.83), and nonsignificant differences between muscles in the shod conditions (p > 0.05). Shod exercise compared to barefoot resulted in lower MG activation (p = 0.001-0.003, d = 0.62-0.63) and non-significant differences in LG activation. These results indicate that barefoot walking and jogging increase MG activation compared to shod conditions, with no differences in LG activation. Additionally, footwear reduces differences between MG and LG.

Rating of Perceived Exertion in the First Repetition is Related to the Total Repetitions Performed in Elastic Bands Training.

Several devices (e.g., linear transducers) have been used for predicting resistance training intensity. However, subjective scales, such as rating of perceived exertion (RPE), are proposed as reliable and easier-to-use tools for monitoring intensity during resistance training. Accordingly, different perceptive scales have been presented in previous research for monitoring intensity during resistance training with elastic bands. The aim was to assess the accuracy and reliability of RPE for quantifying the potential maximal repetitions that could be performed at a given RPE (from 2 to 8 of 10) obtained in the first repetition. For this purpose, 13 recreationally active participants (age: 26.33 [6.52] years, body mass index: 24.97 [5.08] kg/m2) were involved in two familiarization and two experimental sessions. In each session, participants randomly performed one set at each intensity of the first repetition from 2/10 to 8/10 until volitional failure in three different exercises (fly, military press, and push-press). An individual grip width of the elastic band was chosen in each set. The number of repetitions and heart rate were assessed. Significance level was set at p < .05. Repetitions decreased when intensity increased (p < .01) and heart rate was higher in the global exercise (i.e., push-press; p < .05), but nonsignificant differences between intensities were reported. The level of experience influenced the number of repetitions performed (p < .05). Intersession reliability was set from good to excellent (range: 0.64-0.91). Therefore, the RPE of the first repetition is a relevant and reliable parameter related to the total number of repetitions performed for each RPE value in trained participants enrolled in elastic bands resistance training.

Electromyographic activity of posterior kinetic chain muscles during hamstring strengthening exercises.

OBJECTIVES: To compare the muscle activation of the biceps femoris (BF), semitendinosus (ST), gluteus maximus (GM), and contralateral erector spinae (ES) in four specific eccentric hamstring-oriented exercises using overground maximal sprints as an EMG normalization method. DESIGN: cross-sectional study. PARTICIPANTS: twenty-four healthy athletes participated in this study. MAIN OUTCOME MEASURES: The maximum EMG activation of all targeted muscles was measured during maximal sprints and four hamstring exercises: Nordic hamstring (NH), Russian belt (RB), glider (GL) and lying kick (LK). Maximum EMG activation during sprints were used to normalize EMG muscle activation. RESULTS: RB and GL showed lower hamstrings activation (from 15.71% to 39.23% and from 26.34% to 31.23%, respectively), so these exercises may be used as the first step of the retraining. The higher hamstring activation was reached in the NH (from 20.15% to 66.81%) and the LK (from 50.5% to 61.2%). Regarding muscles comparison, BF and ST were the most dependent on the exercise ranging from 26.67% to 62.22%, and from 26.34% to 66.81%, respectively. CONCLUSIONS: Muscle activation is dependent on the exercise procedure. RB and GL should be used as a first step because of their low activation. Instead, NH and LK should be used at the last phases of retraining process. Considering the synergistic activation of the PKC muscles during LK, and because of its unilateral and explosive characteristics, LK seems a suitable exercise for retraining PKC muscles in general.

Effects of pelvic and core strength training on biomechanical risk factors for anterior cruciate ligament injuries.

BACKGROUND: Little is known about the changes in biomechanical risk factors for an anterior cruciate ligament (ACL) injury after participation in a pelvic and core strength training (PCST) program in female team players. METHODS: This is a randomized controlled trial for which a total of 29 female soccer players were recruited from a soccer club and split into two groups, namely, experimental group (EG, N.=18; mean [SD] age, 17.8 [2.0 years], weight 64.0 [6.6] kg and height 1.7 [0.0] m) and control group (control, N.=11; mean [SD] age, 16.2 [1.2] years, weight 61.6 [7.3] kg and height 1.7 [0.0] m). The EG participated in an in-season 8-week PCST program (twice/week). Participants in the CG performed their normal training without additional pelvic and core strengthening. Pre- and postintervention knee frontal plane projection angle (FPPA), hip, knee and ankle peak flexion angles and jump height were collected during bilateral and unilateral drop jumps. RESULTS: PCST significantly reduced FPPA at dynamic landing, in both dominant (-7.1º) and non-dominant lower extremities (-8º). Further, this training significantly increased the peak hip (24.4º) and knee flexion angles (14.94º), but not the peak ankle dorsiflexion angle (P>0.05) which, significantly decreased in the CG (-3.5º). Following the intervention, EG significantly increased measures obtained for both bilateral (2.84 cm) and unilateral jumps (1.33 cm for the dominant leg and 1.22 cm for the non-dominant leg) (P<0.05), not so for CG (P<0.05). CONCLUSIONS: PCST resulted in improvements on ACL injury risk factors and vertical drop jump performance, suggesting that strengthening this body part warrants not only injury prevention, but increases jumping performance.

Accelerometer assessment of physical activity in individuals with paraplegia who do and do not participate in physical exercise.

OBJECTIVE: Our main goal was to measure physical activity (PA) in people with paraplegia. Secondarily, we aimed to establish the relationship between being engaged in physical exercise (PE) and reaching the recommended moderate-to-vigorous physical activity (MVPA) level. We further analyzed the effect of being engaged in PE on the PA levels. DESIGN: Descriptive cross-sectional. SETTING: Spanish associations for individuals with spinal cord injury. PARTICIPANTS: Ninety-six manual wheelchair users with chronic paraplegia. INTERVENTIONS: Participants wore a wrist accelerometer for one week. OUTCOME MEASURES: Levels of PA and sedentary behavior. In addition, participants were classified into two groups, exercisers (EG) and non-exercisers (NEG) to analyze the effect of PE enrollment on the variables. RESULTS: For all participants, a mean (SD) of 5,341.70 (966.4) minutes per week were spent engaged in sedentary behaviors, 2,188.99 (723.9) minutes were spent engaged in light activity, and 206.24 (180.0) minutes were spent engaged in MVPA. There was a significant relationship between PE and reaching the minimum levels of MVPA recommended [x2 (1) = 25.03, P < 0.01]. NEG showed a greater number of minutes per week for sedentary behavior [t (94) = 2.50, P < 0.05, r = 0.25]. The EG spent more than twice as much time doing MVPA than the NEG (263.8 min vs 114.3 min, respectively). CONCLUSIONS: MVPA levels are low in manual wheelchair users who are not regular exercisers, but most of those who self-reported being regular exercisers reach the minimum levels recommended for health benefits. Sedentary behavior is a concern in this population.

Motivation to Physical Exercise in Manual Wheelchair Users With Paraplegia.

Background: Motivation could be considered as a critical factor for being and staying physically active in the spinal cord-injured population. Objectives: Our goals were (1) to describe motivation to exercise in people with paraplegia, comparing those who engage in regular physical exercise with those who do not and (2) to establish whether such motivation is related to the type of physical exercise practiced. Methods: This study was quantitative, cross-sectional descriptive research. One-hundred and six participants with chronic paraplegia completed the Spanish version of the Exercise Motivations Inventory (EMI-2). Participants were divided into the non-exerciser group (NEG) and the exerciser group (EG). EG was subclassified into sports players (SPs) and physical exercisers (PEs). Results: Participants in both EG and NEG presented a similar motivation toward physical exercise. The most important motive to practice or to adhere to exercise in participants with SCI was ill-health avoidance (mean, 8.45; SD, 1.33). Fitness was the second most important motive (ie, nimbleness, flexibility, strength, and endurance). Motives that distinguished EG from NEG included enjoyment and revitalization [t(41.9) = -2.54, p < .05, r = 0.36], competition [t(56.8) = 2.24, p < .05, r = 0.28], and health pressure [t(104) = 3.22, p < .01, r = 0.30]. Furthermore, we found that motivation was related to the type of physical exercise performed. SPs showed a statistically significantly higher score for competition and enjoyment and revitalization than PEs (p < .05). Conclusion: Ill-health avoidance and fitness are the key motivational factors to practice and adhere to physical exercise. Motivation is related to the type of physical exercise performed. Health providers need to understand these factors to promote and sustain long-term adherence to exercise in the SCI population.