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Increases in Knee Extension Muscle Activation but not Peak Torque Following High Intensity Training
Get PDFAutoregulatory progressive resistance exercise (APRE) modulates training intensity in response to individual performance to optimize increases in muscular strength. Muscular activation patterns during maximal torque production can provide additional insight to increased strength following an APRE training intervention. PURPOSE: The purpose of this study was to examine the effects of a 4-week APRE training program on peak torque and muscle activation in the vastus lateralis (VL) during maximal voluntary isokinetic knee extension. METHODS: Eight resistance trained males (age: 21.5 ± 2.3yrs; height: 176.5 ± 6.8cm; weight: 70.3 ± 17.8kg) participated in upper- and lower-body APRE 4-times per week for 4-weeks. Participants performed 2 isokinetic maximal knee extensions at 60°/s to before (PRE) and after (POST) 4-weeks of APRE training. Muscular activation of the VL was recorded using surface electromyography (EMG) and the mean root mean square (RMS) values were analyzed during the concentric phase of the muscle action. Paired samples t-test were used to compare the PRE and POST measurements for torque and average EMG RMS value (mV). RESULTS: There was no significant difference in peak torque from PRE to POST (p = 0.91; 206.49 ± 65.68N to 207.25 ± 58.59N; mean ± SE). Although, there was a significant increase between pre (61.58 ± 22.28mV; mean ± SE) and post (76.49 ± 27.50mV; mean ± SE) EMG amplitudes (p = 0.02). CONCLUSION: The lack of significant changes in peak torque, combined with the increase of EMG amplitude, suggests that APRE may enhance neuromuscular activation efficiency without directly influencing knee extension torque. These findings support the notion that improvements in muscle activation do not always correlate with functional strength gains
Estimation of Constant Power Cycle Ergometer Work Rates Using Responses in Incremental Exercise Tests
Get PDFThe severe exercise intensity domain is defined as the range of work rates that is sustainable for ~2 to 30 minutes and will elicit maximal oxygen uptake (VO2max). Laboratory controlled study designs often require a more stringent timeframe (e.g. 10 - 14 minutes) for achieving VO2max, making selection of individualized work rates a challenging task. PURPOSE: This study aimed to develop a regression equation to predict cycle ergometer work rates that would elicit VO2max and result in fatigue in ~12min (W12min). METHODS: Three women (mean ± SD, age, 23 ± 4 y; height, 168 ± 13 cm; body mass, 69 ± 18 kg) and six men (22 ± 2 y; 182 ± 8 cm; 79 ± 13 kg) performed incremental tests and severe intensity, constant power (range, 102 - 330 watts) tests on a cycle ergometer. Anthropometric measures, power output, and gas exchange data from the incremental tests were investigated as possible predictors of the dependent variable, W12min. Statistical analysis was performed to develop a W12min prediction model using a best-subsets regression method. RESULTS: Regression analysis revealed that absolute VO2 at the first ventilatory threshold (VT1), minute ventilation (VE) at the second ventilatory threshold (VT2), and peak power were significant predictors of W12min (R2 = 0.985, p \u3c 0.001). W12min can be predicted using: W12min = 33.765 + 0.054(VO2 at VT1) – 1.859(VE at VT2) + 0.708(peak power) Variables are expressed in the following units: VO2 in mL∙min-1; VE in BTPS L∙min-1; peak power in watts. CONCLUSION: The regression analysis suggests that W12min can be predicted from the results of an incremental test by utilizing gas exchange variables and power outputs at the VTs and at the end of exercise. This has implications for any research laboratory evaluating responses in this domain with an intervention that alters duration (e.g. hypoxia or ergogenic aid) while still eliciting VO2max
Influence of Back Foot Positioning on Tennis Serve Performance
Get PDFThe sport of tennis involves many different strokes, of which the serve is arguably the most important. The serve begins with feet separated about shoulder width apart with one foot closer to the net. During the foot-up technique, players move their back foot near their front foot while executing the serve. For the foot-back technique, the back foot remains stationary. It is commonly discussed in coaching literature that the use of the foot-up technique allows for enhanced weight transfer producing a more powerful serve while the foot-back technique allows for greater stability and control in the serve. Limited data exists to support these ideas. PURPOSE: To compare force production, ball velocity, and serve depth between the foot-up and foot-back tennis serve techniques among tennis players at the Division III collegiate level. METHODS: Nine Division III collegiate tennis players (20.22 yrs, 1.76 m, 67.86 kg) were recruited to perform five serves using each foot technique and from each side of the court. Peak force (N) was measured using the loadsol pro force insole (novel electronics, inc.) for the front foot and back foot during the loading phase of the tennis serve. An AI-powered shot-tracking app (SwingVision, Inc.) was used to measure ball velocity (mph) and serve depth (defined as distance the ball lands from the front of the service box). RESULTS: Mean (SD) total force was 1753.9 (338.4) N for the foot-up stance and 1667.0 (342.2) N for the foot-back stance. The foot-up serve produced 5.1% greater force (F(1, 8)=3.658, p=0.092 nP2=0.314) in comparison to the foot-back serve. Mean (SD) ball velocity was 70.9 (12.5) mph for the foot-up serve and 69.5 (14.0) mph for the foot-back serve across all participants. The foot-up serve had 1.9% greater ball velocity (t(8)=1.436, p=0.189,Cohen’s d=0.479) than the foot-back serve. Mean (SD) serve depth, from the front of the service box, was 15.7 (0.8) ft for the foot-up serve and 16.0 (1.1) ft for the foot-back serve. The foot-back serve produced a 1.7% deeper (i.e., more advantageous) serve (t(8)=1.047, p=0.326, Cohen’s d=0.349) compared to the foot-up serve. It was found across both serving styles that the front foot had a significantly greater amount of force production in comparison to the back foot (F(1, 8)=11.917, p=0.009, nP2 = 0.598). CONCLUSION: The foot-up and foot-back serve techniques offer moderate but different benefits to serve performance. No previous studies of this nature have been conducted solely among Division III college tennis players, thus making these findings particularly insightful and valuable into the influence of back foot positioning on force production and other performance measures during the tennis serve
Effects of Minimalist Shoe Walking on Plantar Intrinsic Foot Muscle Strength and Size in Normal Healthy Adults: Preliminary Findings
Get PDFWalking in minimalist shoes has been shown to strengthen and increase the size of plantar intrinsic foot muscles (PIM). While previous research has examined the effects of an 8-week minimalist shoe walking protocol in runners, this protocol has not been observed in non-runners. PURPOSE: Examine the effects of an 8-week minimalist shoe training intervention on muscle size and strength in healthy non-runners. METHODS: Ten healthy young adults were recruited for this study and randomized equally to either the control group (age: 21±0.89 yr; BMI: 24.1±3.4 kg/m2) or minimalist shoe group (age: 21.4±2.1 yr; BMI: 23.1±3.4 kg/m2). Participants were included if they had not experienced a lower extremity injury or previously worn minimalist shoes within the past three months and had an average step count of 5,000 steps/day. Participants in the minimalist shoe group were provided with minimalist footwear and instructed to wear them during a progressive 8-week intervention, five days a week, while gradually increasing their daily step count in the shoes. Muscle strength was measured by performing paper grip tests on AMTI force platforms in the anterior-posterior (Fy) and vertical forces (Fz). Averages for peak force were obtained across three trials for the greater toe and lesser toes individually. Images of abductor hallucis (ABDH), flexor digitorum brevis (FDB), and flexor hallucis brevis (FHB) were obtained using an ultrasound. All test measures were performed at baseline, week 4, and week 8. The distributions for the dependent variables were examined for normality. Separate 2x3 repeated measures ANOVAs were used to determine the effects of minimalist shoe walking on increasing muscle strength and size. Alpha was set to ≤0.05 for significance. RESULTS: For greater toes strength there were no significant time (p=.12), group (p=.256), or time*group (p=.339) effects for peak Fz force. Similar results in group (p=.759) and time*group (p=.388) were observed in peak force strength in Fy. However, there was a significant time effect in Fy (p=.031). Likewise, Fz and Fy had no significant time (Fy: p=.28); Fz: p=.13), group (Fy: p=.393; Fz: p=.56) and time*group (Fy: p=.067; Fz: p=.618). Moreover, ABDH, FDB, and FHB, found no significance in time (ABDH: p=069; FDB: p=.153; FHB: p=.67), group (ABDH: p=.19; FDB: p=.26; FHB: p=.831), or time*group (ABDH: p=.270; FDB: p=.433; FHB: p=.714) effects. CONCLUSION: These preliminary findings of an 8-week minimalist shoe walking intervention in healthy non-runners showed no significant effects in either plantar intrinsic muscle strength or size. While not statistically significant, the minimalist shoe group did show some increases in strength and size. Limitations for this study, including unsupervised training may affect the present outcome in addition to the sample size
The Effect of Caffeine on Velocity and Accuracy in Collegiate Baseball Pitchers
Get PDFCaffeine is one of the most widely used drugs among athletes seeking an advantage over opponents. PURPOSE: The purpose of this study was to investigate the effect of caffeine on velocity and accuracy for baseball pitchers. METHODS: Subjects consisted of 20 pitchers from the Texas Lutheran Baseball team. After a warmup, participants threw 10 fastballs. A radar gun that measured miles per hour was used to determine velocity. Only the 5 fastest pitches were used in the data calculations. Strikes and balls were also calculated to determine accuracy. On a different day, subjects were either given a caffeine pill or a placebo and retested. RESULTS: The mean change in accuracy from pretest to post test in the placebo group was .06 with a standard deviation of .21. The mean change in accuracy in the caffeine group was .02 with a standard deviation of .29. A two-sample test for accuracy yielded a t stat of .34, a t critical of 2.26 and a p value of .74. For velocity, the mean change was -.28 for the placebo group with a standard deviation of 2.03. The mean change for the caffeine group was -.42 with a standard deviation of 1.26. The two-sample t test for velocity yielded a t stat of .19, a t critical of 2.26, and a p value of .85. CONCLUSION: The results showed that caffeine made no significant difference in the velocity or accuracy of pitches. While baseball players often take caffeine to provide an advantage in velocity and accuracy, it is possible that the advantage is more psychological as opposed to physiological
Neural or Musculoskeletal: Which System Drives the Age-Related Decline in Walking Economy?
Get PDFOlder adults typically consume 10 to 25% more metabolic energy than young adults while walking (decreased walking economy). The age-related decline in walking economy relates to impaired quality of life and is important to mitigate (or reverse). Yet, it is unestablished which factor(s) govern the age-related decline in the walking economy. Based on recent findings that older adult neural control strategies during walking likely increase their metabolic rate, we sought to test whether age-related metabolic differences persist during simple joint-level tasks. PURPOSE: The purpose of this study is to infer whether the musculoskeletal system directly affects the age-related decline in walking economy. METHODS: Three older adults (avg. ± SD:78.3 ± 1.2 years) and 10 young adults (23.7 ± 0.8 years) participated. Session 1: After familiarization, participants walked on a treadmill at 0.8 m/s and 1.3 m/s for 5-min with seated rest preceding each trial. Session 2: Participants sat on a chair with their right leg secured in a fixed position that emulates joint angles during walking. Participants performed 5-min trials where they cyclically produced fixed-end ankle extension moments following visual and audio feedback (20 and 30 Nm peak moment, 0.75 Hz, 0.5 duty). Next, participants performed the same 5-min trials using their hip extensors while lying with their hip joint at 160°. We randomized the order of ankle and hip trials. We quantified net V̇o2 uptake and V̇co2 production via open-circuit spirometry during all trials and used a standard equation to compute net metabolic power. RESULTS: Consistent with the literature, older adults required 32-36% more net metabolic power to walk than young adults. While cyclically producing joint moments on a dynamometer, older adults consumed 12 to 40 more metabolic power (W) at the ankle and hip than young adults. These greater joint-level metabolic values occurred despite older adults producing 5-14% lower cycle average moments compared to young adults across ankle trials, and 27-48% lower cycle average moments across hip trials. So, despite older adults producing decreased joint moments, they still consumed more metabolic energy to operate their joints than young adults. CONCLUSION: Based on our preliminary findings, it is likely that the aging musculoskeletal system measurably contributes to the age-related decline in the walking economy. Therefore, interventions that maintain youthful musculoskeletal health are warranted to mitigate the age-related decline in walking economy
The Influence of Balance and Strength Training on Gait Symmetry in an Individual with Spastic Quadriplegic Cerebral Palsy
Get PDFCerebral palsy (CP) is a neurodevelopmental disorder that affects muscle tone, movement, and motor skills. Individuals with CP often experience challenges related to balance and postural control, which can affect their ability to perform functional tasks. Individuals with Spastic Quadriplegic CP (SQCP) have difficulty in maintaining balance and symmetrical weight distribution. Structured exercise programs incorporating balance training and strength exercises have been found to be effective in improving postural control and balance in children with CP. PURPOSE: This study aimed to evaluate the influence of balance and strength exercises on gait measures in a young adult with SQCP. METHODS: The participant engaged in training for 80 minutes twice weekly for eight weeks. Each session consisted of a warm-up, gait treadmill training, balance and strength exercises, and cool-down. Intensity, duration and number of rest breaks for each were determined by the participant. Warm-up and cool down stretches consisted of both proprioceptive neuromuscular facilitation (PNF) and active-passive. Separate gait trials were completed at 0 weeks and 4 weeks in which gait measures were assessed while walking on a treadmill at 0.7 speed for 10 strides. Gait was assessed by measuring the duration of stance and swing phase for each foot and peak plantar normal force using loadsol (novel electronics, inc.) force sensing insoles. RESULTS: Pre (week 0) and midpoint (week 4) data was collected, however, due to unforeseen facility circumstances, the researchers were unable to collect post (week 8) intervention data. At baseline, the participant displayed an asymmetric gait in which the left leg spent 60% in the stance phase and 40% swing phase while the right leg spent 80% of the gait cycle in stance and 20% in swing. At the midpoint the participant’s gait showed greater symmetry with both legs spending 80% in stance and 20% in swing. Peak force increased in the right leg from 1.5BW (week 0) to 1.6BW (week 4). CONCLUSION:The combination of balance and strength exercises improved gait symmetry and increased peak force in the right leg. The modest improvements observed in this short period highlight areas for future research to enhance the understanding of gait in adults with CP. The importance of individualized programming to enhance gait lies in the fact that every person with Cerebral Palsy has unique abilities, making it essential to create tailored training programs that promote safe, progressive improvements in physical activities
Acute CrossFit® Exercise Enhances Cognitive Processing Speed and Stabilizes Response Variability in Trained Individuals
No full textHigh-Intensity Functional Training (HIFT), such as CrossFit®, integrates high-intensity, multi-joint movements and has been associated with cognitive enhancement. However, the acute effects of HIFT on inhibitory control in trained individuals remain unstudied. PURPOSE: To examine the acute effects of a single bout of HIFT exercise on inhibitory control in healthy young adults with at least six months of CrossFit training experience. METHODS: Seventeen trained individuals (age: 31.9 ± 10.5 years; 8 females) participated in two 15-minute sessions: (1) a HIFT session consisting of 6 CrossFit®-based exercises (burpees, inverted rows, dumbbell push presses, squat jumps, dumbbell snatch, and leg raises) performed in 20-second all-out intervals with 10-second rest periods, and (2) a control session involving passive reading of neutral materials. Sessions were counterbalanced. Inhibitory control was assessed pre- and post-intervention using the Flanker Task. A repeated-measures ANOVA analyzed Response Accuracy (ACC), Reaction Time (RT), and Standard Deviation of RT (SD of RT) across Time (Pre/Post), Intervention (HIFT/Control), and Congruency (Congruent/Incongruent trials). RESULTS: A significant main effect of Congruency was found for ACC (F (1,16) = 25.857, p \u3c .001, η² = .618), with higher accuracy in congruent trials (99.0%) compared to incongruent trials (96.3%). A significant Time × Intervention × Congruency interaction for RT was observed (F (1,16) = 12.360, p = .003, η² = .436). The CrossFit intervention exhibited significantly faster RTs post-intervention, particularly in incongruent trials, while the control intervention demonstrated no significant improvements. The control intervention did not exhibit significant RT changes in both congruent (p = .283) and incongruent trials (p = .231). For SD of RT, a significant main effect of Congruency was found (F(1,16) = 53.773, p \u3c .001, η² = .771), with greater response variability in incongruent trials compared to congruent trials. CrossFit intervention significantly reduced RT variability in incongruent trials (Pre: 142.62 ± 49.56 ms → Post: 127.68 ± 46.32 ms, p \u3c .05), indicating improved response stability post-exercise. No significant changes in RT variability were observed in congruent trials (Pre: 97.05 ± 30.32 ms → Post: 97.26 ± 33.60 ms, n.s.) or in the control group across conditions. CONCLUSIONS: A single bout of CrossFit® exercise significantly enhanced cognitive processing speed and reduced response variability, particularly under high cognitive load (incongruent trials), while maintaining inhibitory control accuracy. These findings suggest that chronic HIFT exercise may optimize cognitive efficiency and response stability in healthy young adults. Further research should investigate the chronic cognitive effects of HIFT and its potential applicability in untrained populations
Breaking the Injury Cycle: The Role of Comprehensive Integration in Injury Recurrence Among Female Collegiate Athletes
Get PDFFemale collegiate athletes face unique physiological, biomechanical, and socio-cultural factors that may increase their risk of repeated injuries. While first-time injuries have recently been better documented, less is known about whether subsequent injuries involve the same or different types. This gap limits the development of evidence-based prevention strategies that account for injury recurrence patterns in female athletes. PURPOSE: To quantify the prevalence of multiple injuries in female collegiate athletes, assess patterns of injury recurrence versus variation, and examine whether injury accumulation follows a progressive trajectory beyond a single occurrence. METHODS: A retrospective cohort analysis (2021–2024) was conducted using electronic medical records from a convenience sample of Division I NCAA female collegiate basketball, field hockey, lacrosse, soccer, and volleyball players (N = 171; Mage = 19.85, SD = 1.35). Of these, 145 sustained at least one injury and were included in the analysis. Athletes were classified into single-injury and multiple-injury groups based on injury count, regardless of type. All statistical analyses were performed in MATLAB. RESULTS: Among the injured athletes, 77.2% (112/145) sustained ≥2 injuries, a significantly higher proportion than an expected baseline of 50% (z = 6.56, p \u3c .001, Cohen’s h = 0.59). This suggests that once an athlete sustains more than one injury, the likelihood of accumulating additional injuries increases sharply, supporting a threshold effect. Among those multiple-injury athletes, 66.1% (74/112) sustained different types of injuries, while 33.9% experienced the same injury type multiple times. The most frequent injury types among multiple-injury athletes were illness (37.3%), back injuries (29.4%), contusions (29.0%), and muscle strains (26.2%). CONCLUSION: Most multiple-injury athletes sustain different types of injuries, indicating that injury recurrence is largely driven by overlapping risk factors rather than repeated exposure to a single vulnerable area. Once past a single injury, athletes face a compounding risk of accumulating additional, varied injuries, which complicates recovery and long-term performance sustainability. A comprehensive approach that integrates multiple disciplines (e.g., sports medicine, strength and conditioning, biomechanics, sport science, physical therapy, sport psychology, nutrition) to identify and address interconnected physiological, psychological, and environmental factors may be critical for mitigating injury cycles and supporting long-term athletic success in female collegiate sports
Acute Bout of Exercise May Preserve Peripheral Blood Mononuclear Cell Viability Under Oxidative Stress
Get PDFNasal breathing (NB) during exercise induces hypercapnic conditions, which may improve exercise performance. However, the impact of NB on cell viability (CV) remains unexplored. PURPOSE: This study investigated the effects of a single bout of exercise with NB on CV following lipopolysaccharide (LPS)-induced oxidative stress in peripheral blood mononuclear cells (PBMCs). METHODS: Twelve men (age=22.5±3.03 years) were randomly assigned to either the NB group (N=6) or the combined breathing (oral + nasal breathing, CB, N=6) group. Each group performed a graded maximal exercise test (GXT) on a recumbent bike. Plasma samples were collected before and immediately after the GXT to isolate PBMCs, followed by culturing for 12 hours, either with LPS (1µg/mL) or without LPS stimulation. RESULTS: There were no significant differences in CV between the NB and CB groups. CV did not differ between pre-exercise (92.78±1.52%) and immediately post-exercise (93.33±1.76%). However, after 12 hours of culture without LPS, CV was significantly lower in the immediately post-exercise condition (90.60±1.87%) than in the pre-exercise condition (93.45±1.49%, p=0.01). When stimulated with LPS and cultured for 12 hours, CV between the pre-exercise (90.16±2.04%) and immediately post-exercise conditions (91.70±1.50%) was not significantly different. However, both pre-exercise and immediately post-exercise CVs with LPS stimulation were significantly lower (p=0.029) than the pre-exercise CVs without LPS stimulation. CONCLUSION: Decreased CV following maximal exercise may be associated with exercise-induced physiological and biochemical stressors, such as reactive oxygen species, pro-inflammatory cytokines, and metabolic byproducts. Although CV decreased under oxidative stress conditions, a single bout of exercise showed a tendency to preserve viability, which may be attributed to exercise-induced reduction in susceptibility to LPS-induced viability loss by enhancing anti-inflammatory pathways and antioxidant defenses