Submaximal Elastic Resistance Band Tests to Estimate Upper and Lower Extremity Maximal Muscle Strength

Muscle strength assessment is fundamental to track the progress of performance and prescribe correct exercise intensity. In field settings, simple tests are preferred. This study develops equations to estimate maximal muscle strength in upper- and lower-extremity muscles based on submaximal elastic resistance tests. Healthy adults (n = 26) performed a maximal test (1 RM) to validate the ability of the subsequent submaximal tests to determine maximal muscle strength, with elastic bands. Using a within-group repeated measures design, three submaximal tests of 40%, 60%, and 80% during (1) shoulder abduction, (2) shoulder external rotation, (3) hip adduction, and (4) prone knee flexion were performed. The association between number of repetitions and relative intensity was modeled with both 1st and 2nd order polynomials to determine the best predictive validity. For both upper-extremity tests, a strong linear association between repetitions and relative intensity was found (R2 = 0.97–1.00). By contrast, for the lower-extremity tests, the associations were fitted better with a 2nd order polynomial (R2 = 1.00). The results from the present study provide formulas for predicting maximal muscles strength based on submaximal resistance in four different muscles groups and show a muscle-group-specific association between repetitions and intensity.

Rate of Force Development Remains Reduced in the Knee Flexors 3 to 9 Months After Anterior Cruciate Ligament Reconstruction Using Medial Hamstring Autografts: A Cross-Sectional Study

Background: Anterior cruciate ligament (ACL) rupture is a serious injury with a high prevalence worldwide, and subsequent ACL reconstructions (ACLR) appear to be most commonly performed using hamstring-derived (semitendinosus tendon) autografts. Recovery of maximal muscle strength to ≥90% of the healthy contralateral limb is considered an important criterion for safe return to sports. However, the speed of developing muscular force (ie, the rate of force development [RFD]) is also important for the performance of many types of activities in sports and daily living, yet RFD of the knee extensor and flexor muscles has apparently never been examined in patients who undergo ACLR with hamstring autograft (HA). Purpose: To examine potential deficits in RFD, maximal muscle strength (ie, maximal voluntary isometric contraction [MVIC]), and functional capacity of ACLR-HA limbs in comparison with the healthy contralateral leg and matched healthy controls 3 to 9 months after surgery. Study Design: Cross-sectional study; Level of evidence: 3. Methods: A total of 23 young patients who had undergone ACLR-HA 3 to 9 months earlier were matched by age to 14 healthy controls; both groups underwent neuromuscular screening. Knee extensor and flexor MVIC and RFD, as well as functional capacity (single-leg hop for distance [SLHD] test, timed single-leg sit-to-stand [STS] test), were assessed on both limbs. Furthermore, patient-reported knee function (Knee injury and Osteoarthritis Outcome Score) was assessed. Results: Knee extensor and flexor MVIC and RFD were markedly compromised in ACLR-HA limbs compared with healthy contralateral limbs (MVIC for extensor and flexor, 13% and 26%, respectively; RFD, 14%-17% and 32%-39%) and controls (MVIC, 16% and 31%; RFD, 14%-19% and 30%-41%) ( P < .05-.001). Further, ACLR-HA limbs showed reduced functional capacity (reduced SLHD and STS performance) compared with contralateral limbs (SLHD, 11%; STS, 14%) and controls (SLHD, 20%; STS, 31%) ( P < .01-.001). Strength (MVIC) and functional (SLHD) parameters were positively related to the duration of time after surgery ( P < .05), although this relationship was not observed for RFD and STS. Conclusion: Knee extensor and flexor RFD and maximal strength, as well as functional single-leg performance, remained substantially reduced in ACLR-HA limbs compared with noninjured contralateral limbs and healthy controls 3 to 9 months after reconstructive surgery.

Sex difference in fatigability of knee extensor muscles during sustained low-level contractions

This study investigated whether the sex difference in fatigability of the knee extensors (KE) is explained by the sex difference in fatigue-induced changes in the shear modulus of one or more muscles of KE in 18 young men and 23 young women. The shear moduli of the resting rectus femoris and medial and lateral vastus muscles (VL) were measured before and after a sustained contraction at 20% peak torque during a maximal voluntary isometric contraction of KE until the endurance limit, in addition to evoked torque and voluntary activation (VA%). The fatigue-induced decrease in maximal muscle strength was more prominent in men than in women. Only the VL shear modulus for men increased after the fatiguing task, and a sex difference was observed in the percentage change in the VL shear modulus before and after the fatiguing task. The fatigue-induced decreased ratio was greater for men than for women in evoked torque, but not in VA%. These results suggest that although peripheral and central fatigue both influenced the fatigue-induced decrease in maximal muscle strength regardless of sex, the sex difference in KE fatigability is explained by that in peripheral fatigue, particularly the degree of peripheral VL fatigue.

Are changes in physical fitness, body composition and weight associated with exercise attendance and dropout among fitness club members? Longitudinal prospective study

ObjectivesThe primary aim of the present study was to investigate if changes in physical fitness, body composition and weight are associated with exercise attendance and dropout among fitness club members. Secondary, we wanted to identify motives for fitness club membership and exercise.SettingNew members at 25 fitness clubs in Oslo, Norway.ParticipantsIn total, 125 new fitness club members were recruited. Eligible criteria were <4 weeks of membership, untrained (exercising <60 min once a week) and ≥18 years. At inclusion, and after 3 (n=87) and 12 months (n=64), participants answered a questionnaire (including motives for membership and exercise, and attendance) and performed measurements of maximum oxygen uptake (VO2max), one repetition maximum (bench press and leg press), body composition and weight. In total, 56 participants underwent measurements at all time points. Based on self-reported attendance, participants were divided into three groups: regular attendance (≥2 sessions per week), low attendance (<2 sessions per week) and exercise dropout (no sessions the last month).ResultsAt 3 months, regular attendees had significantly higher VO2max than dropout (6.54 mL/min/kg, 95% CI 2.00 to 11.07, p=0.003). At 12 months, a difference in VO2max of 5.32 mL/min/kg (95% CI −0.08 to 10.72, p=0.054) was found between regular attendees and dropout, and between regular and low exercise attendance (6.17 mL/min/kg, 95% CI 0.19 to 12.15, p=0.042). VO2max was the only factor showing an association with attendance. No differences or associations were observed in maximal muscle strength or body composition between the three groups. Primary motive for fitness club membership and exercise was increase in physical fitness (92.8%).ConclusionsVO2max was the only factor associated with exercise attendance at two time points. Increased physical fitness was primary motive for fitness club membership and exercise.