Functional Performance and Tendon Morphology After Operative or Nonoperative Treatment of Achilles Tendon Ruptures.

Background: While controversy remains as to the relative benefit of operative (OM) versus non-operative management (NOM) of Achilles tendon (AT) ruptures (ATR), few studies have examined the effect on high impact maneuvers such as jumping and hopping. Hypothesis/Purpose: The purpose of this study was to determine if functional performance including strength, jumping, and hopping outcomes differed between OM and NOM of acute ATR. The secondary objective was to assess the degree of association between AT morphology and performance outcomes. Study Design: Retrospective cohort with a single prospective evaluation. Methods: All patients were treated at an institutional secondary care center. Eligible participants (n=12 OM; 12 NOM) who were treated with OM or NOM of ATR within three weeks of injury were evaluated a minimum 20 months following ATR. AT length, thickness and gastrocnemius muscle thickness were assessed with B-mode ultrasound. Isokinetic plantar flexor strength, hop tests and countermovement and drop jumps were completed. Two-way ANOVAS were completed on all tests with unilateral values, independent t-tests were used for bilateral outcomes, and linear regressions were completed to assess the relationship between normalized AT length and performance. Results: Affected limb AT was elongated and thickened (p\<0.01), gastrocnemius was atrophied (p\< 0.01) and angle-specific plantar flexor torque was reduced at 120°/s when measured at 20° plantar flexion (p = 0.028). Single leg drop vertical jump was higher in OM (p = 0.015) with no difference for hop and jump tests. AT length was related to plantar flexor torque but had no relationship with hopping performance. Conclusions: Hop test performance was maintained despite plantarflexion weakness, gastrocnemius atrophy, and AT elongation. This may be the result of compensatory movement patterns. AT length holds limited explanatory power in plantar flexor strength, although this relationship should be evaluated further. Level of Evidence: Level III.

The impact of COVID-19 on national hockey league players' return to play.

OBJECTIVE: Evaluate the on-ice performance and return to play (RTP) rate following COVID-19 for National Hockey League (NHL) players during the 2020-21 season. METHODS: Players with COVID-19 during the abbreviated 2020-21 season were identified using publicly accessible online sources. Demographics and on-ice metrics were accessed using the NHL's online statistics website. The length of time, rate of RTP, and games missed due to COVID-19 were analyzed. Primary outcomes included average time on ice (TOI) per game (TOI/G), average TOI per shift (TOI/S), and points per game (PPG) compared at different timepoints including pre- and post-COVID-19. RESULTS: A total of 73 players (47 forwards, 18 defensemen, 8 goalies) had a documented COVID-19 diagnosis during the abbreviated 2020-21 season. Players missed an average of 5.6 games (14.7 days) due to COVID-19. The post-COVID-19 RTP rate was 97.3%, including playoffs. No differences were found in TOI/G between the pre- (15.7 ± 3.9 min) and post-COVID-19 (15.8 ± 3.4 min, p = 0.874) or in the first (15.8 ± 4.0 min) and second week (15.9 ± 3.8 min, p = 0.925) returned. TOI/shift did not change from pre- (45.6 ± 5.3 sec) to post-COVID-19 (46.7 ± 4.6 sec, p = 0.035) or in first (46.2 ± 5.4 sec) and second week post-COVID-19 (46.2 ± 4.8 sec, p = .854). No differences were identified for PPG between career, pre-COVID-19, and post-COVID-19 (0.44 vs 0.38 vs 0.41; p = 0.274). CONCLUSION: RTP post-COVID was markedly high for NHL players. While the effects of COVID-19 on specific physiological measures remains to be elucidated, this study found NHL players do not have reduced performance following COVID-19.

Characterizing the Practices of Canadian Orthopedic Surgeons in the Management of patients With Anterior Glenohumeral Instability.

OBJECTIVE: To determine the practice patterns of Canadian orthopedic surgeons in the management of patients with anterior glenohumeral instability (AGHI). DESIGN: Cross-sectional survey. SETTING: Canada. PATIENTS OR OTHER PARTICIPANTS: Canadian orthopedic surgeons with membership in the Canadian Orthopedic Association or Canadian Shoulder and Elbow Surgeon group who had managed at least 1 patient with AGHI in the previous year. INTERVENTIONS: A survey including demographics and questions on the management of patients with AGHI was completed. Statistical comparisons (χ 2 ) were completed with responses stratified using the instability severity index score (ISIS) in practice, years of practice, and surgical volumes. MAIN OUTCOME MEASURES: Summary statistics were compiled, and response frequencies were considered for consensus (75%). Case series responses were stratified on use of the ISIS in practice, years of experience, and annual procedure volumes (χ 2 , P < 0.05). RESULTS: Eighty orthopedic surgeons responded, with consensus on areas of diagnostic workup of AGHI, nonoperative management, and operative techniques. There was no consensus on indications for soft tissue and bony augmentation or postoperative management. There was no difference in practices based on the use of ISIS, years in practice, or surgical volumes. CONCLUSIONS: Canadian orthopedic surgeons manage AGHI consistently with consensus achieved in preoperative diagnostics and operative techniques, although debate remains as to the indications for soft tissue and bony augmentation procedures.

Fiber-Type-Specific Hypertrophy with the Use of Low-Load Blood Flow Restriction Resistance Training: A Systematic Review.

Emerging evidence indicates that the use of low-load resistance training in combination with blood flow restriction (LL-BFR) can be an effective method to elicit increases in muscle size, with most research showing similar whole muscle development of the extremities compared to high-load (HL) training. It is conceivable that properties unique to LL-BFR such as greater ischemia, reperfusion, and metabolite accumulation may enhance the stress on type I fibers during training compared to the use of LLs without occlusion. Accordingly, the purpose of this paper was to systematically review the relevant literature on the fiber-type-specific response to LL-BFR and provide insights into future directions for research. A total of 11 studies met inclusion criteria. Results of the review suggest that the magnitude of type I fiber hypertrophy is at least as great, and sometimes greater, than type II hypertrophy when performing LL-BFR. This finding is in contrast to HL training, where the magnitude of type II fiber hypertrophy tends to be substantially greater than that of type I myofibers. However, limited data directly compare training with LL-BFR to nonoccluded LL or HL conditions, thus precluding the ability to draw strong inferences as to whether the absolute magnitude of type I hypertrophy is indeed greater in LL-BFR vs. traditional HL training. Moreover, it remains unclear as to whether combining LL-BFR with traditional HL training may enhance whole muscle hypertrophy via greater increases in type I myofiber cross-sectional area.

Knee flexor strength and symmetry vary by device, body position and angle of assessment following ACL reconstruction with hamstring grafts at long-term follow-up.

PURPOSE: Persistent deficits in knee flexor strength following harvest of semitendinosus and gracilis for anterior cruciate ligament reconstruction are inconsistent in the literature. Variation in methodology, including measuring torque at higher knee flexion angles may partially explain these discrepant findings. The objective of this study was to determine whether positioning (seated vs supine), consideration of peak or joint-angle-specific torque or device (Isokinetic Dynamometer vs NordBord Hamstring Dynamometer) impact the magnitude of knee flexor strength differences between limbs. METHODS: Participants (n = 31, 44.2 ± 10.7 years,) who were at 14 ± 4.4 years follow-up for unilateral ACL reconstruction with semitendinosus/gracilis grafts completed the ACL Quality of Life outcome and an assessment including isokinetic concentric knee extensor and flexor strength in seated and supine with peak torque and torque at 60° (T60) and 75° (T75) knee flexion measured, followed by an eccentric Nordic Hamstring Curl. RESULTS: Isokinetic concentric knee flexor torque was reduced in supine relative to seated, on the reconstructed limb against the unaffected, and at higher degrees of knee flexion relative to peak torque (T60 and T75 against peak torque). Limb symmetry varied by methodology (F(6,204) = 8.506, p = 0.001) with reduced symmetry in supine T75 against all measures (71.1 ± 16.5%, p < 0.05), supine T60 against seated peak torque (82.7 ± 14.2%, p < 0.05), and the NordBord was lower than seated peak torque that was not statistically significant (83.9 ± 12.8%, n.s.). Knee extensor peak (r2 = 0.167 (F(1,27) = 5.3, p = 0.03) and Nordic curl eccentric torque (r2 = 0.267, F(2,26) = 4.736, p = 0.02) were predictors of ACL-QoL score, although a combined model did not improve over Nordic torque alone. CONCLUSION: Limb symmetry cannot be assumed in clinical practice across differing assessment methods for knee flexor strength as deficits are greatest in the supine position with torque measured at 75° knee flexion. Isokinetic knee extensor and eccentric knee flexor torque during the Nordic hamstring curl were predictors of ACL-QoL scoring and should be considered alongside patient-reported outcomes for patients following ACL reconstruction with hamstring grafts. LEVEL OF EVIDENCE: Level IV.

Postoperative weight-bearing restrictions and rehabilitation protocols after hip arthroscopy for femoroacetabular impingement: a systematic review.

Despite recent increased interest in hip arthroscopy for the management of femoroacetabular impingement (FAI), there is little evidence to guide weight-bearing recommendations and rehabilitation postoperatively. The primary objective of this study was to determine if sufficient evidence exists to recommend specific weight-bearing restrictions postoperatively. This study was registered with PROSPERO (CRD42021247741). PubMed, MEDLINE and Embase were searched on 3 March 2023 for Level I-IV studies including patients over the age of 18 years, with a minimum 1-year follow-up and reporting of a weight-bearing status, a patient-reported outcome measure (PROM) and a clinical outcome. Meta-analysis was precluded due to heterogeneity in the included studies, and a descriptive analysis was undertaken. Methodological quality and risk of bias were assessed with the methodological index for non-randomized studies (MINORS). Twenty-four studies including 2231 patients who underwent hip arthroscopy for treatment of FAI were included (follow-up interval 33.2 ± 24.7 months). Most articles (62.5%) were case series. There were seven terms describing weight-bearing recommendations, with 83% being some variation of 'partial weight-bearing'. Eight PROMs were reported, with 83% using the modified Harris Hip Score and 87.5% of studies reporting reoperation rates. Only 75% of studies reported rehabilitation protocols. The average MINORS score was 11.07 ± 1.10 out of 16 for non-comparative studies and 18.22 ± 1.48 out of 24 for comparative studies. The reporting of weight-bearing status, clinical outcomes, PROMs and rehabilitation parameters remains poor. At present, sufficient comparative evidence does not exist to make specific weight-bearing recommendation postoperatively.

No differences found in long-term outcomes of a randomized controlled trial comparing ipsilateral versus contralateral hamstring graft in ACL reconstruction.

PURPOSE: Contralateral graft harvest in primary ACL reconstruction is relatively uncommon and the long-term comparative of this approach relative to ipsilateral harvest has not been described. The purpose of this study was to evaluate ACL graft and contralateral rupture following ipsilateral or contralateral semitendinosus and gracilis (STG) graft harvest at follow-up of a minimum 10 years post-reconstruction in the treatment of a complete ACL tear. METHODS: Patients from a previous randomized trial were evaluated. The primary outcome measures were ipsilateral and contralateral reinjury as well as the International Knee Documentation Committee (IKDC) knee assessment form, the ACL Quality of Life questionnaire (ACL-QoL) and the Tegner activity scale. Participants completed four different single-leg hop tests and concentric knee flexion and extension strength were assessed on an isokinetic dynamometer. RESULTS: Of the original 100 patients, 50 patients (41.3 ± 9.5 years of age, 31 males, 19 females) reported on re-injury at 12.6 ± 1.4 years post-operative. Thirty-eight patients returned for full assessment and 12 responded by mail or phone survey. There were no differences between groups for graft rupture, contralateral injury, ACL-QoL score, IKDC categorization, or anterior tibial translation, though both groups experienced a reduction in the Tegner Activity Scale from their preinjury scores. There was no difference in knee flexor and extensor isokinetic concentric strength, or single leg hop test performance. Knee flexor strength limb symmetry index was reduced when measured in the supine relative to the seated position in both groups, indicating persistent deficits in knee flexor strength when measured in the supine position. CONCLUSION: Contralateral hamstring harvest does not put patients at an increased risk of a contralateral ACL tear and long-term outcomes of ACL reconstruction do not differ based on the side of graft harvest. Contralateral STG harvest may provide a safe alternative surgical option for select patients. LEVEL OF EVIDENCE: Level II.

Comparison of Common Methodologies for the Determination of Knee Flexor Muscle Strength.

BACKGROUND: Knee flexion strength may hold important clinical implications for the determination of injury risk and readiness to return to sport following injury and orthopedic surgery. A wide array of testing methodologies and positioning options are available that require validation prior to clinical integration. The purpose of this study was to 1) investigate the validity and test-retest reliability of isometric knee flexion strength measured by a fixed handheld dynamometer (HHD) apparatus compared to a Biodex Dynamometer (BD), 2) determine the impact of body position (seated versus supine) and foot position (plantar- vs dorsiflexed) on knee flexion peak torque and 3) establish the validity and test-retest reliability of the NordBord Hamstring Dynamometer. STUDY DESIGN: Validity and reliability study, test-retest design. METHODS: Forty-four healthy participants (aged 27 ± 4.8 years) were assessed by two raters over two testing sessions separated by three to seven days. Maximal isometric knee flexion in the seated and supine position at 90o knee flexion was measured with both a BD and an externally fixed HHD with the foot held in maximal dorsiflexion or in plantar flexion. The validity and test-retest reliability of eccentric knee flexor strength on the NordBord hamstring dynamometer was assessed and compared with isometric strength on the BD. RESULTS: Level of agreement between HHD and BD torque demonstrated low bias (bias -0.33 Nm, SD of bias 13.5 Nm; 95% LOA 26.13 Nm, -26.79 Nm). Interrater reliability of the HHD was high, varying slightly with body position (ICC range 0.9-0.97, n=44). Isometric knee flexion torque was higher in the seated versus supine position and with the foot dorsiflexed versus plantarflexed. Eccentric knee flexion torque had a high degree of correlation with isometric knee flexion torque as measured via the BD (r=0.61-0.86). The NordBord had high test-retest reliability (0.993 (95%CI 0.983-0.997, n=19) for eccentric knee flexor strength, with an MDC95 of 26.88 N and 28.76 N for the left and right limbs respectively. CONCLUSION: Common measures of maximal isometric knee flexion display high levels of correlation and test-retest reliability. However, values obtained by an externally fixed HHD are not interchangeable with values obtained via the BD. Foot and body position should be considered and controlled during testing. LEVEL OF EVIDENCE: 2b.

Complications of Superior Capsule Reconstruction for the Treatment of Functionally Irreparable Rotator Cuff Tears: A Systematic Review.

PURPOSE: The purpose of this systematic review is to characterize the complications associated with superior capsule reconstruction (SCR) for the treatment of functionally irreparable rotator cuff tears (FIRCTs). METHODS: This systematic review was completed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Two independent reviewers completed a search of PubMed, Embase, and Medline databases. Studies were deemed eligible for inclusion if they reported postoperative outcomes of arthroscopic SCR for FIRCTs and considered at least 1 postoperative complication. Statistical heterogeneity was quantified via the I2 statistic. Due to marked heterogeneity, pooled proportions were not reported. All complications and patient-reported outcomes were described qualitatively. RESULTS: Fourteen studies met the inclusion/exclusion criteria. The overall complication rate post-SCR ranged from 5.0% to 70.0% (I2 = 84.9%). Image-verified graft retear ranged from 8% to 70%, I2 = 79.4%), with higher rates reported when SCR was performed using allograft (19%-70%, I2 76.6%) compared to autograft (8%-29%, I2 = 66.1%). Reoperation (0%-36%, I2 = 73.4%), revision surgeries (0%-21%, I2 = 81.2%), medical complications (0%-5%, I2 = 0.0%), and infections (0%-5%, I2 = 0.0%) were also calculated. CONCLUSIONS: SCR carries a distinct complication profile when used for the treatment of FIRCTs. The overall rate of complications ranged from 5.0% to 70.0%. The most common complication is graft retear with higher ranges in allografts (19%-70%) compared to autografts (8%-29%). The majority of studies reported at least 1 reoperation (range, 0%-36%), most commonly for revision to reverse shoulder arthroplasty. LEVEL OF EVIDENCE: Level IV, systematic review of Level IV or better investigations.

Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis.

Schoenfeld, BJ, Grgic, J, Ogborn, D, and Krieger, JW. Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. J Strength Cond Res 31(12): 3508-3523, 2017-The purpose of this article was to conduct a systematic review of the current body of literature and a meta-analysis to compare changes in strength and hypertrophy between low- vs. high-load resistance training protocols. Searches of PubMed/MEDLINE, Cochrane Library, and Scopus were conducted for studies that met the following criteria: (a) an experimental trial involving both low-load training [≤60% 1 repetition maximum (1RM)] and high-load training (>60% 1RM); (b) with all sets in the training protocols being performed to momentary muscular failure; (c) at least one method of estimating changes in muscle mass or dynamic, isometric, or isokinetic strength was used; (d) the training protocol lasted for a minimum of 6 weeks; (e) the study involved participants with no known medical conditions or injuries impairing training capacity. A total of 21 studies were ultimately included for analysis. Gains in 1RM strength were significantly greater in favor of high- vs. low-load training, whereas no significant differences were found for isometric strength between conditions. Changes in measures of muscle hypertrophy were similar between conditions. The findings indicate that maximal strength benefits are obtained from the use of heavy loads while muscle hypertrophy can be equally achieved across a spectrum of loading ranges.

Hypertrophic Effects of Concentric vs. Eccentric Muscle Actions: A Systematic Review and Meta-analysis.

Schoenfeld, BJ, Ogborn, DI, Vigotsky, AD, Franchi, MV, and Krieger, JW. Hypertrophic effects of concentric vs. eccentric muscle actions: A systematic review and meta-analysis. J Strength Cond Res 31(9): 2599-2608, 2017-Controversy exists as to whether different dynamic muscle actions produce divergent hypertrophic responses. The purpose of this paper was to conduct a systematic review and meta-analysis of randomized controlled trials comparing the hypertrophic effects of concentric vs. eccentric training in healthy adults after regimented resistance training (RT). Studies were deemed eligible for inclusion if they met the following criteria: (a) were an experimental trial published in an English-language refereed journal; (b) directly compared concentric and eccentric actions without the use of external implements (i.e., blood pressure cuffs) and all other RT variables equivalent; (c) measured morphologic changes using biopsy, imaging (magnetic resonance imaging, computerized tomography, or ultrasound), bioelectrical impedance, and/or densitometry; (d) had a minimum duration of 6 weeks; and (e) used human participants without musculoskeletal injury or any health condition that could directly, or through the medications associated with the management of said condition, be expected to impact the hypertrophic response to resistance exercise. A systematic literature search determined that 15 studies met inclusion criteria. Results showed that eccentric muscle actions resulted in a greater effect size (ES) compared with concentric actions, but results did not reach statistical significance (ES difference = 0.25 ± 0.13; 95% confidence interval: -0.03 to 0.52; p = 0.076). The mean percent change in muscle growth across studies favored eccentric compared with concentric actions (10.0% vs. 6.8, respectively). The findings indicate the importance of including eccentric and concentric actions in a hypertrophy-oriented RT program, as both have shown to be effective in increasing muscle hypertrophy.

Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis.

The purpose of this paper was to systematically review the current literature and elucidate the effects of total weekly resistance training (RT) volume on changes in measures of muscle mass via meta-regression. The final analysis comprised 34 treatment groups from 15 studies. Outcomes for weekly sets as a continuous variable showed a significant effect of volume on changes in muscle size (P = 0.002). Each additional set was associated with an increase in effect size (ES) of 0.023 corresponding to an increase in the percentage gain by 0.37%. Outcomes for weekly sets categorised as lower or higher within each study showed a significant effect of volume on changes in muscle size (P = 0.03); the ES difference between higher and lower volumes was 0.241, which equated to a percentage gain difference of 3.9%. Outcomes for weekly sets as a three-level categorical variable (<5, 5-9 and 10+ per muscle) showed a trend for an effect of weekly sets (P = 0.074). The findings indicate a graded dose-response relationship whereby increases in RT volume produce greater gains in muscle hypertrophy.

A Comparison of Increases in Volume Load Over 8 Weeks of Low-Versus High-Load Resistance Training.

BACKGROUND: It has been hypothesized that the ability to increase volume load (VL) via a progressive increase in the magnitude of load for a given exercise within a given repetition range could enhance the adaptive response to resistance training. OBJECTIVES: The purpose of this study was to compare changes in volume load (VL) over eight weeks of resistance training (RT) in high-versus low-load protocols. MATERIALS AND METHODS: Eighteen well-trained men were matched according to baseline strength were randomly assigned to either a low-load RT (LOW, n = 9) where 25 - 35 repetitions were performed per exercise, or a high-load RT (HIGH, n = 9) where 8 - 12 repetitions were performed per exercise. Both groups performed three sets of seven exercises for all major muscles three times per week on non-consecutive days. RESULTS: After adjusting for the pre-test scores, there was a significant difference between the two intervention groups on post-intervention total VL with a very large effect size (F (1, 15) = 16.598, P = .001, ηp(2) = .525). There was a significant relationship between pre-intervention and post-intervention total VL (F (1, 15) = 32.048, P < .0001, ηp(2) = .681) in which the pre-test scores explained 68% of the variance in the post-test scores. CONCLUSIONS: This study indicates that low-load RT results in greater accumulations in VL compared to high-load RT over the course of 8 weeks of training.

Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis.

BACKGROUND: A number of resistance training (RT) program variables can be manipulated to maximize muscular hypertrophy. One variable of primary interest in this regard is RT frequency. Frequency can refer to the number of resistance training sessions performed in a given period of time, as well as to the number of times a specific muscle group is trained over a given period of time. OBJECTIVE: We conducted a systematic review and meta-analysis to determine the effects of resistance training frequency on hypertrophic outcomes. METHODS: Studies were deemed eligible for inclusion if they met the following criteria: (1) were an experimental trial published in an English-language refereed journal; (2) directly compared different weekly resistance training frequencies in traditional dynamic exercise using coupled concentric and eccentric actions; (3) measured morphologic changes via biopsy, imaging, circumference, and/or densitometry; (4) had a minimum duration of 4 weeks; and (5) used human participants without chronic disease or injury. A total of ten studies were identified that investigated RT frequency in accordance with the criteria outlined. RESULTS: Analysis using binary frequency as a predictor variable revealed a significant impact of training frequency on hypertrophy effect size (P = 0.002), with higher frequency being associated with a greater effect size than lower frequency (0.49 ± 0.08 vs. 0.30 ± 0.07, respectively). Statistical analyses of studies investigating training session frequency when groups are matched for frequency of training per muscle group could not be carried out and reliable estimates could not be generated due to inadequate sample size. CONCLUSIONS: When comparing studies that investigated training muscle groups between 1 to 3 days per week on a volume-equated basis, the current body of evidence indicates that frequencies of training twice a week promote superior hypertrophic outcomes to once a week. It can therefore be inferred that the major muscle groups should be trained at least twice a week to maximize muscle growth; whether training a muscle group three times per week is superior to a twice-per-week protocol remains to be determined.

Motor unit recruitment cannot be inferred from surface EMG amplitude and basic reporting standards must be adhered to.

The study by Jenkins et al. attempted to elucidate the mechanisms behind the findings of Mitchell et al. (J Appl Physiol 113(1):71-77, 2012). However, we believe the work of Jenkins et al. contains methodological issues, does not meet electromyographic reporting standards, and deduces conclusions beyond which can be interpreted from the data provided.

Effects of Low- vs. High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men.

The purpose of this study was to compare the effect of low- versus high-load resistance training (RT) on muscular adaptations in well-trained subjects. Eighteen young men experienced in RT were matched according to baseline strength and then randomly assigned to 1 of 2 experimental groups: a low-load RT routine (LL) where 25-35 repetitions were performed per set per exercise (n = 9) or a high-load RT routine (HL) where 8-12 repetitions were performed per set per exercise (n = 9). During each session, subjects in both groups performed 3 sets of 7 different exercises representing all major muscles. Training was performed 3 times per week on nonconsecutive days, for a total of 8 weeks. Both HL and LL conditions produced significant increases in thickness of the elbow flexors (5.3 vs. 8.6%, respectively), elbow extensors (6.0 vs. 5.2%, respectively), and quadriceps femoris (9.3 vs. 9.5%, respectively), with no significant differences noted between groups. Improvements in back squat strength were significantly greater for HL compared with LL (19.6 vs. 8.8%, respectively), and there was a trend for greater increases in 1 repetition maximum (1RM) bench press (6.5 vs. 2.0%, respectively). Upper body muscle endurance (assessed by the bench press at 50% 1RM to failure) improved to a greater extent in LL compared with HL (16.6 vs. -1.2%, respectively). These findings indicate that both HL and LL training to failure can elicit significant increases in muscle hypertrophy among well-trained young men; however, HL training is superior for maximizing strength adaptations.

Daily chocolate milk consumption does not enhance the effect of resistance training in young and old men: a randomized controlled trial.

Older and younger men completed 12 weeks of resistance training and ingested either 500 mL of chocolate milk or placebo daily. Training increased strength in both age groups (p < 0.05), with no supplementation effect. Type I muscle fibre area increased with training (p = 0.008) with no effect of age or supplementation. Type II fibre area increased (p = 0.014) in young men only with no supplementation effect. Chocolate milk did not enhance skeletal muscle hypertrophy following training.

Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis.

BACKGROUND: Maximizing the hypertrophic response to resistance training (RT) is thought to be best achieved by proper manipulation of exercise program variables including exercise selection, exercise order, length of rest intervals, intensity of maximal load, and training volume. An often overlooked variable that also may impact muscle growth is repetition duration. Duration amounts to the sum total of the concentric, eccentric, and isometric components of a repetition, and is predicated on the tempo at which the repetition is performed. OBJECTIVE: We conducted a systematic review and meta-analysis to determine whether alterations in repetition duration can amplify the hypertrophic response to RT. METHODS: Studies were deemed eligible for inclusion if they met the following criteria: (1) were an experimental trial published in an English-language refereed journal; (2) directly compared different training tempos in dynamic exercise using both concentric and eccentric repetitions; (3) measured morphologic changes via biopsy, imaging, and/or densitometry; (4) had a minimum duration of 6 weeks; (5) carried out training to muscle failure, defined as the inability to complete another concentric repetition while maintaining proper form; and (6) used human subjects who did not have a chronic disease or injury. A total of eight studies were identified that investigated repetition duration in accordance with the criteria outlined. RESULTS: Results indicate that hypertrophic outcomes are similar when training with repetition durations ranging from 0.5 to 8 s. CONCLUSIONS: From a practical standpoint it would seem that a fairly wide range of repetition durations can be employed if the primary goal is to maximize muscle growth. Findings suggest that training at volitionally very slow durations (>10s per repetition) is inferior from a hypertrophy standpoint, although a lack of controlled studies on the topic makes it difficult to draw definitive conclusions.