The Short Grit Scale (GRIT-S) Does Not Relate to Acute Muscular Endurance Performance.

Grit has been previously presented as a personality trait that reflects an individual's perseverance of effort and consistency of interest for achieving their long-term goals. In resistance training this could mean that a "grittier" individual may perform more repetitions at a given intensity as they are better able to overcome metabolic and neuromuscular fatigue. Thus, the purpose of this study was to examine if grit was related to back squat muscular endurance performance. Fifty-eight resistance-trained males and females volunteered for participation (age = 23±3 yrs; body height = 172.53 ± 8.64 cm; body mass = 80.64 ± 6.49 kg). The grit of each participant was assessed via the Short Grit Scale (GRIT-S), and muscular endurance performance was tested via completion of a back squat set to volitional failure at 70% of the participant's one-repetition maximum. Spearman rho or Pearson's correlations, depending on normality, were used with 1000 bootstrapped replicate samples and revealed no relationship between GRIT-S scores (3.78 ± 0.52) and repetitions performed (14 ± 4) in a combined cohort of all 58 individuals (ρ = -0.051), males only (r = 0.057) or females only (ρ = -0.441). Supplementary investigation of the data also showed that the five "best" performers (i.e. the five individuals who performed the most repetitions) tended to have lower GRIT-S scores than the five "worst" performers. The results of the current study suggest that the GRIT-S has limited value in the context of muscular endurance performance. The skewed range of GRIT-S scores (2.75-5.0) observed in this investigation, also highlights the potential for social desirability to bias one's self-perception of grit.

Impact of Cognitive Measures and Sleep on Acute Squat Strength Performance and Perceptual Responses Among Well-Trained Men and Women.

ABSTRACT: Haischer, MH, Cooke, DM, Carzoli, JP, Johnson, TK, Shipherd, AM, Zoeller, RF, Whitehurst, M, and Zourdos, MC. Impact of cognitive measures and sleep on acute squat strength performance and perceptual responses among well-trained men and women. J Strength Cond Res 35(2S): S16-S22, 2021-This study assessed the efficacy of currently used assessments for sleep, anxiety, and stress in predicting 1-repetition maximum (1RM) back squat performance. Fifty-three men (age, 23 ± 3 years; body mass, 86.67 ± 13.93 kg; training age, 6.0 ± 2.5 years; 1RM = 163.5 ± 39.5 kg) and 15 women (age, 21 ± 1.5 years; body mass, 63.34 ± 9.6 kg; training age, 4 ± 1.5 years; 1RM = 81.5 ± 12.5 kg) participated. Subjects completed the Daily Analysis of Life Demands for Athletes (DALDA), the revised Competitive State Anxiety Inventory-2 (CSAI-2R), and Oviedo Sleep Questionnaire (OSQ) to evaluate stress, anxiety, and sleep, respectively. Subjects then completed the perceived self-efficacy (PSE) scale, to predict what loads they were 100, 75, and 50% confident that they could lift for a 1RM; then completed 1RM testing with rating of perceived exertion (RPE) and average concentric velocity (ACV) obtained on each attempt. The performance-dependent variable was calculated by subtracting the PSE responses from the actual 1RM (1RM-PSE difference). Bootstrapping with 1,000 replicate samples was used with linear regression to increased robustness of the statistical analyses, and 95% confidence intervals (CIs) were calculated. Hours of sleep was an inverse predictor of ACV (p = 0.014; 95% CI = 0.046 to-0.011) and a positive predictor of RPE (p = 0.005; 95% CI = 0.068-0.342). Furthermore, the hypersomnia subscale of the OSQ was a negative predictor of 1RM-PSE difference at 50% confidence (p = 0.028; 95% CI = -3.507 to -0.528), and CSAI-2R total score was a negative predictor of RPE at 1RM (p = 0.043; 95% CI = -0.041 to -0.003); however, the DALDA did not exhibit any significant relationships. These data highlight the importance of monitoring anxiety and sleep when assessing readiness for maximal strength performance.

Low-volume acute multi-joint resistance exercise elicits a circulating brain-derived neurotrophic factor response but not a cathepsin B response in well-trained men.

This study examined if acute multi-joint resistance exercises (RE; back squat, bench press, and deadlift) to volitional failure elicited a postexercise increase in the circulating response of biomarkers associated with neuroprotection. Thirteen males (age: 24.5 ± 3.8 years, body mass: 84.01 ± 15.44 kg, height: 173.43 ± 8.57 cm, training age: 7.1 ± 4.2 years) performed 4 sets to failure at 80% of a 1-repetition maximum on the squat, bench press, and deadlift in successive weeks. The measured biomarkers were brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), cathepsin B (CatB), and interleukin 6 (IL-6). Biomarkers were assessed immediately before and 10-min after exercise. There was a main time effect (pre-exercise: 24.00 ± 0.61 to postexercise: 27.38 ± 0.48 ng/mL; p < 0.01) for BDNF with increases in the deadlift (p = 0.01) and bench press (p = 0.01) conditions, but not in the squat condition (p = 0.21). There was a main time effect (pre-exercise: 0.87 ± 0.16 to postexercise: 2.03 ± 0.32 pg/mL; p < 0.01) for IL-6 with a significant increase in the squat (p < 0.01), but not the bench press (p = 0.88) and deadlift conditions (p = 0.24). No main time effect was observed for either CatB (p = 0.62) or IGF-1 (p = 0.56). In summary, acute multi-joint RE increases circulating BDNF. Further, this investigation is the first to report the lack of a transient change of CatB to an acute RE protocol. Novelty Low-volume RE to failure can increase BDNF. Resistance training does not confer an acute Cat B response.

Hippocampal Growth Factor and Myokine Cathepsin B Expression following Aerobic and Resistance Training in 3xTg-AD Mice.

Aerobic training (AT) can support brain health in Alzheimer's disease (AD); however, the role of resistance training (RT) in AD is not well established. Aside from direct effects on the brain, exercise may also regulate brain function through secretion of muscle-derived myokines. Aims. This study examined the effects of AT and RT on hippocampal BDNF and IGF-1 signaling, ß-amyloid expression, and myokine cathepsin B in the triple transgenic (3xTg-AD) model of AD. 3xTg-AD mice were assigned to one of the following groups: sedentary (Tg), aerobic trained (Tg+AT, 9 wks treadmill running), or resistance trained (Tg+RT, 9 wks weighted ladder climbing) (n = 10/group). Rotarod latency and strength were assessed pre- and posttraining. Hippocampus and skeletal muscle were collected after training and analyzed by high-resolution respirometry, ELISA, and immunoblotting. Tg+RT showed greater grip strength than Tg and Tg+AT at posttraining (p < 0.01). Only Tg+AT improved rotarod peak latency (p < 0.01). Hippocampal IGF-1 concentration was ~15% greater in Tg+AT and Tg+RT compared to Tg (p < 0.05); however, downstream signals of p-IGF-1R, p-Akt, p-MAPK, and p-GSK3ß were not altered. Cathepsin B, hippocampal p-CREB and BDNF, and hippocampal mitochondrial respiration were not affected by AT or RT. ß-Amyloid was ~30% lower in Tg+RT compared to Tg (p < 0.05). This data suggests that regular resistance training reduces ß-amyloid in the hippocampus concurrent with increased concentrations of IGF-1. Both types of training offered distinct benefits, either by improving physical function or by modifying signals in the hippocampus. Therefore, inclusion of both training modalities may address central defects, as well as peripheral comorbidities in AD.

Time course of recovery is similar for the back squat, bench press, and deadlift in well-trained males.

This study examined the time course of recovery following resistance exercise sessions in the back squat, bench press, and deadlift. Twelve well-trained males (age: 24.5 ± 3.8 years, body mass: 84.01 ± 15.44 kg, training age: 7.1 ± 4.2 years) performed 4 sets to failure at 80% of a 1-repetition maximum (1RM) on the squat, bench press, and deadlift in successive weeks. The bench press was always performed in week 2 with the squat and deadlift order counterbalanced between weeks 1 and 3. Indirect muscle damage and performance fatigue was assessed immediately before and after exercise and at 24 h, 48 h, 72 h, and 96 h postexercise. Outcome measures included limb swelling, joint range of motion, delayed onset muscle soreness, average concentric velocity (ACV) at 70% of 1RM, creatine kinase, lactate dehydrogenase, and cell-free DNA (cfDNA). Most measures demonstrated a main time effect (p < 0.05) within conditions; however, no between condition (p > 0.05) differences existed. ACV decreased in the squat condition for up to 72 h (p = 0.02, -8.61%) and in the bench press (p < 0.01, -26.69%) immediately postexercise but did not decline during the deadlift condition (p > 0.05). There was a main time effect for increased cfDNA in the squat (p < 0.01) and bench press (p < 0.05), but not the deadlift (p = 0.153). Further, immediately postexercise increases in cfDNA were directly related (p < 0.05) to changes in ACV in all 3 conditions. These results suggest that the deadlift does not result in greater muscle damage and recovery time than the squat and bench press following volume-type training in well-trained men. Further, acute changes in cfDNA may predict performance during the recovery period.

Body Mass and Femur Length Are Inversely Related to Repetitions Performed in the Back Squat in Well-Trained Lifters.

Cooke, DM, Haischer, MH, Carzoli, JP, Bazyler, CD, Johnson, TK, Varieur, R, Zoeller, RF, Whitehurst, M, and Zourdos, MC. Body mass and femur length are inversely related to repetitions performed in the back squat in well-trained lifters. J Strength Cond Res 33(3): 890-895, 2019-The purpose of this research note was to examine whether relationships existed between anthropometrics (body mass, body fat percentage [BF%], and femur length) and descriptive characteristics (age and sex) with repetitions performed to failure at 70% of 1 repetition maximum (1RM) in the back squat. Fifty-eight subjects (males = 43, females = 15; age: 23 ± 3 years, training age: 5.5 ± 2.5 years, body mass: 80.65 ± 16.34 kg, BF%: 10.98 ± 3.53%, and femur length: 47.1 ± 2.6 cm) completed a 1RM squat followed by one set to failure at 70% of 1RM. Total repetitions performed at 70% of 1RM were 14 ± 4 (range: 6-26). Bivariate correlations showed significant inverse relationships between body mass (r = -0.352, p = 0.003), BF% (r = -0.278, p = 0.014), and femur length (r = -0.265, p = 0.019), with repetitions performed. No significant relationships existed between age and sex (p > 0.05), with repetitions performed. All these variables entered into a standard multivariate regression. The model R was 0.200, and body mass had the largest influence (p = 0.057) because relative importance analysis demonstrated body mass to contribute to 43.87% of the variance (of the R) in repetitions performed. No other variable was significant or approached significance (p > 0.05). Our results reveal that body mass, BF%, and femur length all are inversely related to repetitions performed at 70% of 1RM in the back squat.

RPE vs. Percentage 1RM Loading in Periodized Programs Matched for Sets and Repetitions.

Purpose: To investigate differences between rating of perceived exertion (RPE) and percentage one-repetition maximum (1RM) load assignment in resistance-trained males (19-35 years) performing protocols with matched sets and repetitions differentiated by load-assignment. Methods: Participants performed squats then bench press 3x/weeks in a daily undulating format over 8-weeks. Participants were counterbalanced by pre-test 1RM then assigned to percentage 1RM (1RMG, n = 11); load-assignment via percentage 1RMs, or RPE groups (RPEG, n = 10); participant-selected loads to reach target RPE ranges. Ultrasonography determined pre and post-test pectoralis (PMT), and vastus lateralis muscle thickness at 50 (VLMT50) and 70% (VLMT70) femur-length. Results: Bench press (1RMG +9.64 ± 5.36; RPEG + 10.70 ± 3.30 kg), squat (1RMG + 13.91 ± 5.89; RPEG + 17.05 ± 5.44 kg) and their combined-total 1RMs (1RMG + 23.55 ± 10.38; RPEG + 27.75 ± 7.94 kg) increased (p < 0.05) in both groups as did PMT (1RMG + 1.59 ± 1.33; RPEG +1.90 ± 1.91 mm), VLMT50 (1RMG +2.13 ± 1.95; RPEG + 1.85 ± 1.97 mm) and VLMT70 (1RMG + 2.40 ± 2.22; RPEG + 2.31 ± 2.27 mm). Between-group differences were non-significant (p > 0.05). Magnitude-based inferences revealed 79, 57, and 72% chances of mean small effect size (ES) advantages for squat; ES 90% confidence limits (CL) = 0.50 ± 0.63, bench press; ES 90% CL = 0.28 ± 0.73, and combined-total; ES 90% CL = 0.48 ± 0.68 respectively, in RPEG. There were 4, 14, and 6% chances 1RMG had a strength advantage of the same magnitude, and 18, 29, and 22% chances, respectively of trivial differences between groups. Conclusions: Both loading-types are effective. However, RPE-based loading may provide a small 1RM strength advantage in a majority of individuals.