Comparison Between Foam Rolling With and Without Vibration on Passive and Active Plantar Flexor Muscle Properties

Although foam rolling interventions with and without vibration have been used to increase flexibility in the field of sports, their effects on passive and active properties remain unclear. Hence, this study aimed to investigate the effects of foam rolling interventions on range of motion (ROM), shear elastic modulus, plantar flexor muscle strength, and jump performance. This randomized, controlled, crossover study included 16 healthy male participants who visited the laboratory three times (control condition, foam rolling condition, and vibration foam rolling condition), each with an interval of >72 h. In both foam rolling and vibration foam rolling conditions, participants were instructed to perform 60-s bouts of intervention for three sets, with 30-s rest between each set. In the vibration foam rolling condition, the intensity of vibration was set at a frequency of 48 Hz. Dorsiflexion (DF) ROM, shear elastic modulus, plantar flexor muscle strength, and drop jump height were determined before and after the rolling intervention. Our results showed a similar increase in DF ROM (p < 0.01, d = 0.51; p < 0.01, d = 0.65, respectively) and passive torque at DF ROM (p = 0.02, d = 0.51 and p < 0.01, d = 0.65, respectively) after foam rolling and vibration foam rolling. Medial gastrocnemius shear elastic modulus decreased only after vibration foam rolling (p < 0.01, d = 0.44). No significant main effects of time were observed in maximal voluntary isometric contraction torque (F = 2.0, p = 0.15, η_p² = 0.119) and drop jump height (F = 1.5, p = 0.24, η_p² = 0.091) after both interventions. Maximal voluntary concentric contraction torque showed a significant main effect of time (F = 7.59, p = 0.02, η_p² = 0.336). However, only after foam rolling, the maximal voluntary concentric contraction torque significantly decreased (p = 0.01, d = 0.39). Our results suggest that vibration foam rolling effectively alters passive muscle properties without decreasing muscle strength and performance.

Acute Effect of Vibration Roller With and Without Rolling on Various Parts of the Plantar Flexor Muscle

A single use of a vibration foam roller likely increases the range of motion (ROM) without decreasing muscle strength and athletic performance. However, to date, no study compared the effects of a vibration roller with and without rolling on various parts of the plantar flexor muscle. Therefore, this study aimed to compare the effects of the vibration foam roller with rolling or without rolling at the muscle-tendon junction (MTJ) or the muscle belly on dorsiflexion (DF) ROM, passive torque at DF ROM, shear elastic modulus, muscle strength, and jump performance. Fifteen healthy young males performed the following three conditions: (1) vibration rolling over the whole muscle-tendon unit, (2) static vibration on muscle belly, and (3) static vibration on MTJ for three-set 60-s vibration in random order. In this study, DF ROM, passive torque, shear elastic modulus, muscle strength, and single-leg drop jump were measured before and immediately after the interventions. The DF ROM and passive torque at DF ROM were increased after all three conditions, whereas the shear elastic modulus was decreased after vibration rolling and static vibration on the muscle belly, but not following static vibration of the MTJ. In addition, there were no significant changes in muscle strength and jump performance in any group. Our results showed that vibration with rolling or static vibration on muscle belly could be effective to improve ROM and muscle stiffness without adverse effects of muscle strength and athletic performance.

Effects of Adding Inter-Set Static Stretching to Flywheel Resistance Training on Flexibility, Muscular Strength, and Regional Hypertrophy in Young Men

Performing static stretching (SS) during resistance training (RT) rest periods is posited to potentiate muscular adaptations, but the literature is scarce on the topic. Thus, the purpose of this study was to investigate the effects of adding inter-set SS to a lower-limb flywheel RT program on joint flexibility, muscular strength, and regional hypertrophy. Sixteen untrained male adults (21 ± 1 y) completed the study, where they performed progressive flywheel bilateral squatting twice a week for 5 weeks. One leg of each participant was randomly allocated to perform SS during the inter-set rest period (RT+SS), while the other leg served as control (RT only). Before and after the intervention, knee flexion range of motion; knee extension isometric, concentric, and eccentric peak torque; 1-repetition maximum; and muscle thickness of the lower-limb muscles were assessed. Following the training period, additional effects were observed for the inter-set SS side on increasing joint flexibility (p < 0.05), whereas the average increase in strength measures was 5.3% for the control side, and 10.1% for the inter-set SS side, however, SS intervention induced significantly greater gains only for knee extension isometric strength, but not for dynamic 1-RM, concentric, and eccentric tests. Hamstrings and gluteus maximus did not hypertrophy with training; increases quadriceps muscle thickness depended on the site/portion analyzed, but no significant difference was observed between legs (average: RT = 7.3%, RT+SS = 8.0%). The results indicate that adding inter-set SS to RT may provide large gains in flexibility, slightly benefits for muscular strength (especially for isometric action), but do not impact muscle hypertrophy in untrained young men.

Isokinetic concentric quadriceps and hamstring strength variables from the NFL Scouting Combine are not predictive of hamstring injury in first-year professional football players

BACKGROUND

There are conflicting reports regarding the association between isokinetic concentric quadriceps and hamstring strength deficits and ratios and risk for hamstring injuries in athletes.

PURPOSE

To determine if isokinetic concentric Cybex data collected during the annual National Football League (NFL) Scouting Combine are predictive of hamstring injury in professional American football players during their first season.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

All 32 NFL teams identified players selected during the first 5 rounds of the NFL annual draft who had hamstring injuries during their first professional season. Of these, 164 players with 172 injuries also had Cybex data from the previous year's Combine. Analyses compared injured legs with contralateral uninjured legs and also injured players with uninjured controls using a database of Cybex data from all players who participated in the NFL Scouting Combine from 2006 to 2011.

RESULTS

No Cybex strength variable differentiated the injured legs from the contralateral uninjured legs or injured players from uninjured controls, even after taking into account days lost from activity. Mean ± SD peak torque for the injured and contralateral uninjured sides was as follows: 315.7 ± 70.0 and 313.5 ± 68.3 N · m, respectively (P = .773, paired t test), for quadriceps and 203.0 ± 42.4 and 205.3 ± 42.5 N · m, respectively (P = .608, paired t test), for hamstrings. The sensitivity and specificity for the hamstrings-to-quadriceps ratio predicting hamstring injury were 0.513 (95% confidence interval, 0.419-0.607) and 0.524 (0.495-0.554), indicating that the hamstrings-to-quadriceps ratio was not a useful predictor of injury (calculation used the mean ± SD ratio for injured legs, 0.656 ± 0.133). Side-to-side peak torque differences were also not predictive of injury, with more than a 10% difference (plus or minus) occurring commonly in both injured and uninjured players for quadriceps (53% prevalence for both injured and uninjured) and hamstrings (injured, 41% prevalence; uninjured, 43% prevalence).

CONCLUSION

Isokinetic strength data collected from collegiate players at the NFL Scouting Combine were not useful for predicting risk of hamstring injury in subsequent professional NFL competition. These data call into question commonly accepted assumptions about risk factors for hamstring injury, at least for elite collegiate American football players, when the temporal relationship between Cybex testing and actual injury is several months.