Edited by: Francis Degache, University of Applied Sciences and Arts of Western Switzerland, Switzerland
Reviewed by: Fiorenzo Moscatelli, University of Foggia, Italy; Marc Dauty, Centre Hospitalier Universitaire (CHU) de Nantes, France
This article was submitted to Exercise Physiology, a section of the journal Frontiers in Physiology
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In boxing the impact of strength has an important role in the physiological profile (
Muscles imbalances of IR and ER of shoulder are important for the injury prevention, with the ratio of ER/IR for healthy subjects in low isokinetic concentric velocity at 30–60°/s being 2/3 (
The myodynamic bilateral ratios from 0 to 10% are considered normal, 10–20% possibly abnormal, whereas greater than 20% abnormal (
Forty male amateur Greek boxers (age 25.5 ± 3.5 years; height 177 ± 6 cm; body weight 78.8 ± 8.8 kg) and 10 non-athletes (control group) participated voluntarily by competing in the National Hellenic Boxing Championship (Table
Physical characteristics of subjects by performance group (Elite, B and C).
Group ( |
Age (yrs) | Height (cm) | Weight (kg) |
---|---|---|---|
Elite (22) | 25.7 (2.9) | 179 (6) | 80.6 (8.3) |
B (11) | 26.4 (4.1) | 176 (5) | 75.4 (6.5) |
C (7) | 22.9 (3.6) | 176 (8) | 78.4 (12.5) |
Total (40) | 25.5 (3.5) | 178 (6) | 78.8 (8.8) |
Control (10) | 22.0 (2.0) | 172 (6) | 70.6 (5.5) |
All participants were free of injury for at least 6 months prior to testing procedures, having no previous experience in isokinetic testing of the shoulder. They were informed about testing procedures, the benefits and potential risks of research, and signed informed consent form in accordance with the guidelines on human rights prior to testing session. They were examined at the beginning of training year (September 2011–2015). The institutional review board of the Faculty of Human Movement & Quality of Life, Peloponnese University, Sparta, Greece, approved all procedures of this study.
The isokinetic dynamometer Kin-ComTM (Chattem, Chattanooga, TN, United States) was used for testing and was calibrated at 60, 120, and 180°/s. Outcome measures were (i) peak torque (PT) of concentric (con) and eccentric (ecc) contractions of dominant (D) and non-dominant (ND) limbs, (ii) bilateral (BL), (iii) unilateral (UL), and (iv) functional ratios. The evaluation of the shoulder using isokinetic dynamometry has demonstrated high to very high reliability, 0.74–0.97 (
Each participant performed a 5-min standard warm up (
Before considering the maximal PT, participants performed a specific warm-up consisting of five repetitions (including three submaximal and two maximum con/ecc contractions) according to a recommended intermittent warm-up protocol (
Experimental set-up. max, maximum; rep, repetitions; IR, internal rotator; ER, external rotator; 60, 120, and 180°/s, angular velocity; con, concentric; ecc, eccentric.
The results of PT of con and ecc were expressed in both absolute (N.m) and relative to body mass values (N.m.kg-1), with the range of motion for the IR from 90 to 0° degrees and vice versa for ER 0 to 90°. The minimum strength value was set at 25 N for all measurements. Furthermore, BL (%) was calculated using the formula 100 × [PT(D)–PT(ND)]/PT(D), whereas UL (%) was 100 × ER/IR. Two functional ratios were considered: (a) IRecc/ERcon, and (b) ERecc/IRcon.
The statistical analyses were conducted using the statistical package SPSS v IBM 23.0 (SPSS, Chicago, IL, United States 223). The average of the three attempts in each test was used for further analysis. For the normality of the data we used the Kolmogorov-Smirnov test. The data were expressed as means and standard deviations (SD). The analysis of the measurements was performed using descriptive statistics, and one-way analysis of variance (ANOVA) and
A large main effect of sport on PT was observed (
Peak torque (PT) of internal (IR), and external rotators (ER) of shoulder against 60, 120, and 180°/s in boxers and control group. ∗difference between boxers and control group at
Peak torque (in N.m.kg-1) values in internal (IR) and external rotators (ER) of shoulders in boxers and control group.
IR |
ER |
|||||||
---|---|---|---|---|---|---|---|---|
con |
ecc |
con |
ecc |
|||||
Boxers | Control | Boxers | Control | Boxers | Control | Boxers | Control | |
60D | 0.69 ± 0.08‡ | 0.59 ± 0.04 | 0.85 ± 0.13‡ | 0.65 ± 0.04 | 0.40 ± 0.06 | 0.38 ± 0.03 | 0.52 ± 0.08† | 0.43 ± 0.03 |
60ND | 0.64 ± 0.08† | 0.56 ± 0.04 | 0.76 ± 0.11‡ | 0.62 ± 0.04 | 0.38 ± 0.05 | 0.36 ± 0.03 | 0.49 ± 0.07† | 0.41 ± 0.03 |
120D | 0.60 ± 0.08† | 0.51 ± 0.04 | 0.77 ± 0.12‡ | 0.58 ± 0.04 | 0.36 ± 0.06 | 0.34 ± 0.03 | 0.48 ± 0.07‡ | 0.39 ± 0.02 |
120ND | 0.56 ± 0.07† | 0.48 ± 0.04 | 0.69 ± 0.10‡ | 0.55 ± 0.04 | 0.35 ± 0.05 | 0.32 ± 0.03 | 0.46 ± 0.07‡ | 0.37 ± 0.03 |
180D | 0.56 ± 0.08† | 0.48 ± 0.05 | 0.73 ± 0.11‡ | 0.55 ± 0.05 | 0.34 ± 0.05 | 0.31 ± 0.03 | 0.47 ± 0.06‡ | 0.37 ± 0.03 |
180ND | 0.51 ± 0.07∗ | 0.46 ± 0.05 | 0.69 ± 0.10‡ | 0.51 ± 0.06 | 0.33 ± 0.04† | 0.29 ± 0.02 | 0.45 ± 0.05‡ | 0.33 ± 0.04 |
A large main effect of performance group on PT was found (
Peak torque (in N.m) values in internal (IR) and external rotators (ER) of shoulders among groups of athletes (Elite, B and C).
IR |
ER |
|||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
con |
Ecc |
con |
ecc |
|||||||||
Elite | B | C | Elite | B | C | Elite | B | C | Elite | B | C | |
60D | 56.7 ± 4.8∗†### | 51.7 ± 3.7## | 49.9 ± 2.0 | 68.5 ± 7.5†### | 67.6 ± 8.9†## | 56.4 ± 5.0# | 32.1 ± 2.9 | 31.2 ± 4.4# | 28.6 ± 3.7 | 42.0 ± 4.2†## | 40.7 ± 5.4†# | 34.1 ± 5.7 |
60ND | 51.7 ± 4.0∗† | 47.4 ± 1.8 | 47.3 ± 2.3 | 61.2 ± 5.5† | 59.9 ± 5.6† | 52.9 ± 3.7 | 31.1 ± 3.7 | 29.9 ± 3.4 | 27.3 ± 3.6 | 40.1 ± 3.1† | 38.2 ± 3.7† | 32.4 ± 4.5 |
120D | 49.8 ± 5.3∗†### | 44.8 ± 2.8## | 43.0 ± 1.2 | 64.6 ± 7.5†### | 59.0 ± 7.3†### | 49.1 ± 2.9 | 29.5 ± 3.6†# | 28.4 ± 3.2†# | 24.3 ± 2.8 | 39.3 ± 3.6† | 36.5 ± 2.8† | 31.4 ± 2.1 |
120ND | 45.1 ± 5.3 | 41.5 ± 3.0 | 42.0 ± 3.2 | 56.5 ± 5.8† | 53.1 ± 5.6† | 45.9 ± 4.0 | 28.5 ± 2.9† | 26.9 ± 2.6 | 24.3 ± 3.0 | 38.6 ± 4.1∗† | 35.1 ± 1.9† | 30.3 ± 1.6 |
180D | 46.6 ± 5.0∗†### | 40.6 ± 3.6# | 38.9 ± 5.2 | 62.0 ± 5.8∗†### | 54.9 ± 4.6†## | 46.1 ± 3.5 | 28.2 ± 2.8∗†### | 25.3 ± 2.2## | 25.0 ± 2.8 | 39.5 ± 2.8∗†### | 34.8 ± 1.5†## | 30.7 ± 1.1 |
180ND | 41.1 ± 4.0 | 38.0 ± 3.5 | 40.0 ± 6.2 | 56.9 ± 4.5∗† | 51.6 ± 5.3 | 46.3 ± 2.4 | 26.6 ± 2.4∗ | 23.7 ± 1.9 | 25.0 ± 2.8 | 38.0 ± 2.7∗† | 33.5 ± 1.8 | 31.0 ± 1.2 |
Furthermore, a large main effect of performance group on PT was shown (
Peak torque in relative to body mass values (N.m.kg-1) in internal (IR) and external rotators (ER) of shoulders by performance group (Elite, B and C).
IR |
ER |
|||||||||||
con |
Ecc |
con |
ecc |
|||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Elite | B | C | Elite | B | C | Elite | B | C | Elite | B | C | |
60D | 0.71 ± 0.08 | 0.69 ± 0.07 | 0.65 ± 0.12 | 0.85 ± 0.10 | 0.90 ± 0.14C | 0.74 ± 0.13 | 0.40 ± 0.04 | 0.42 ± 0.08 | 0.37 ± 0.06 | 0.52 ± 0.05 | 0.55 ± 0.10C | 0.45 ± 0.11 |
60ND | 0.65 ± 0.08 | 0.63 ± 0.05 | 0.62 ± 0.12 | 0.76 ± 0.09 | 0.80 ± 0.11 | 0.69 ± 0.14 | 0.39 ± 0.04 | 0.40 ± 0.06 | 0.35 ± 0.06 | 0.50 ± 0.05C | 0.51 ± 0.07C | 0.42 ± 0.10 |
120D | 0.62 ± 0.07 | 0.60 ± 0.06 | 0.56 ± 0.09 | 0.81 ± 0.10C | 0.79 ± 0.11C | 0.64 ± 0.10 | 0.37 ± 0.06 | 0.38 ± 0.05 | 0.31 ± 0.05 | 0.49 ± 0.06C | 0.49 ± 0.05 | 0.41 ± 0.08 |
120ND | 0.56 ± 0.07 | 0.55 ± 0.06 | 0.55 ± 0.10 | 0.70 ± 0.08C | 0.71 ± 0.10 | 0.60 ± 0.13 | 0.36 ± 0.05 | 0.36 ± 0.04 | 0.31 ± 0.05 | 0.48 ± 0.06C | 0.47 ± 0.05C | 0.39 ± 0.06 |
180D | 0.58 ± 0.09 | 0.54 ± 0.06 | 0.50 ± 0.08 | 0.78 ± 0.10C | 0.73 ± 0.09C | 0.60 ± 0.08 | 0.35 ± 0.05 | 0.34 ± 0.04 | 0.33 ± 0.06 | 0.49 ± 0.05C | 0.47 ± 0.04C | 0.40 ± 0.06 |
180ND | 0.52 ± 0.07 | 0.51 ± 0.06 | 0.52 ± 0.10 | 0.71 ± 0.08C | 0.69 ± 0.10 | 0.60 ± 0.10 | 0.33 ± 0.04 | 0.32 ± 0.04 | 0.33 ± 0.06 | 0.47 ± 0.05C | 0.45 ± 0.04 | 0.40 ± 0.06 |
Boxers had higher BL than control group (
Bilateral ratio of internal (IR) and external rotators (ER) of shoulder against 60, 120, and 180°/s in boxers and control group. ∗difference between boxers and control group at
With regards to performance groups, elite boxers and B scored higher than C (
Bilateral ratios (%) in internal and external rotators of shoulders by performance group.
IR |
ER | ||||||||||
Con |
ecc |
con |
ecc | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Elite | B | C | Elite | B | C | Elite | B | C | Elite | B | C |
8.6 ± 6.1 | 8.1 ± 5.5 | 5.1 ± 4.5 | 3.3 ± 7.5 | 3.6 ± 5.4 | 4.2 ± 7.9 | 10.1 ± 8.6 | 10.7 ± 9.7 | 6.0 ± 6.2 | 4.1 ± 5.6 | 5.7 ± 6.2 | 4.4 ± 9.2 |
9.3 ± 6.9 | 7.3 ± 7.1 | 2.4 ± 5.2 | 2.9 ± 7.4 | 4.8 ± 6.1 | -0.2 ± 7.9 | 12.3 ± 4.6 | 9.7 ± 5.4 | 6.7 ± 6.2 | 1.8 ± 5.5 | 3.4 ± 6.6 | 3.2 ± 9.0 |
11.3 ± 6.3∗ | 6.3 ± 7.0∗ | -2.8 ± 5.2 | 5.5 ± 4.9∗ | 5.9 ± 5.8 | -0.1 ± 4.6 | 7.9 ± 7.8 | 6.0 ± 5.2 | -0.8 ± 8.6 | 3.7 ± 3.7∗ | 3.9 ± 3.4∗ | -1.0 ± 3.6 |
Unilateral was lower in boxers than in control group in ER/IRcon at 60D and 120D, and in ER/IRecc at 60D, 120D and 180D (
Unilateral ratio of internal (IR) and external rotators (ER) of shoulder against 60, 120, and 180°/s in boxers and control group. ∗difference between boxers and control group at
No difference was observed in UL among performance groups (
Unilateral ratios of internal (IR) and external rotators (ER) of shoulder against 60, 120, and 180°/s among performance groups (Elite, B and C) of boxers.
ER/IRcon |
ER/IRecc |
|||||
---|---|---|---|---|---|---|
Elite | B | C | Elite | B | C | |
60D | 57.2 ± 8.0 | 60.4 ± 8.1 | 57.3 ± 6.5 | 61.6 ± 5.4 | 60.5 ± 6.9 | 60.3 ± 6.1 |
60ND | 60.5 ± 8.8 | 63.2 ± 7.1 | 57.9 ± 8.7 | 65.8 ± 5.3 | 63.9 ± 5.3 | 61.3 ± 7.4 |
120D | 59.6 ± 7.5 | 63.4 ± 7.2 | 56.5 ± 6.3 | 61.2 ± 5.1 | 62.3 ± 5.7 | 64.1 ± 4.8 |
120ND | 63.6 ± 6.3 | 65.1 ± 6.5 | 58.0 ± 7.7 | 68.5 ± 5.4 | 66.5 ± 5.3 | 66.5 ± 7.5 |
180D | 60.9 ± 5.6 | 62.5 ± 6.6 | 64.7 ± 5.4 | 63.8 ± 3.2 | 63.7 ± 3.8 | 66.7 ± 2.7 |
180ND | 64.9 ± 5.1 | 63.0 ± 7.7 | 63.0 ± 5.5 | 66.8 ± 2.9 | 65.1 ± 4.0 | 67.0 ± 2.1 |
A main effect of sport on IRecc/ERcon was observed with boxers presenting higher functional ratio than control group (
Functional ratio against 60, 120, and 180°/s in boxers and control group. ∗difference between boxers and control group at
With regards to performance group, Elite and B had higher functional ratio than C for 180 of IRecc/ERcon, and 60ND, 120ND, and 180ND of ERecc/IRcon (
Functional ratios against 60, 120, and 180°/s by performance group (Elite, B and C).
IRecc/ERcon |
ERecc/IRcon |
|||||
---|---|---|---|---|---|---|
Elite | B | C | Elite | B | C | |
60D | 2.14 ± 0.25 | 2.22 ± 0.54 | 1.99 ± 0.19 | 0.74 ± 0.09 | 0.76 ± 0.08 | 0.70 ± 0.09 |
60ND | 1.99 ± 0.28 | 2.03 ± 0.34 | 1.96 ± 0.24 | 0.78 ± 0.07∗ | 0.81 ± 0.08∗ | 0.69 ± 0.09 |
120D | 2.22 ± 0.37 | 2.12 ± 0.48 | 2.04 ± 0.25 | 0.79 ± 0.07 | 0.81 ± 0.06∗ | 0.73 ± 0.04 |
120ND | 1.99 ± 0.24 | 2.00 ± 0.35 | 1.92 ± 0.31 | 0.86 ± 0.09∗ | 0.85 ± 0.07∗ | 0.73 ± 0.07 |
180D | 2.21 ± 0.25∗ | 2.19 ± 0.25∗ | 1.87 ± 0.25 | 0.85 ± 0.07 | 0.86 ± 0.07 | 0.80 ± 0.11 |
180ND | 2.15 ± 0.22∗ | 2.19 ± 0.33∗ | 1.87 ± 0.18 | 0.93 ± 0.08∗ | 0.89 ± 0.09 | 0.79 ± 0.12 |
The PT of boxers in IR and ER were stronger than the control group that affects the importance of these muscles on the strength of the boxers and on the performance of the athletes with similar kinetic chain (
The PT were higher in the dominant limb with a statistical significant difference at the three speeds, stressing the importance of this edge in coaching and training performance (
The bilateral ratios were approximately 6–10% for the IR and about 3–6% for the ER which are below 10% and are considered normal values for the myodynamic ratios (
The UL ratios of CON and ECC were lower (0.58–0.64) at all speeds except of 120 and 180°/s ND ECC, which considered below normal of 0.66 of concentric with injury risk (
The functional ratios of IR ECC/ER CON of the men athletes (2.0–2.2) were statistical significant with the control group ND at all speeds, and highlights the importance of both limbs in this phase of kinetic chain especially at the high speed because both limbs were with no statistical significant similar ratios. Also, the ratios of men athletes of ER ECC/IR CON (0.74–0.89) were statistical significant with the control group at 180°/s and between D and ND at all speeds, which maybe link with the comeback of the limb.
The low bilateral ratios of the IR contractions explain the support of the rotators on the performance which is the contribution of the fast movements of the punches on the target specially of the dominant limb with higher strength and the very low ratios of ER explain the possibility of both muscles to produce more power and faster returns of the punches. In the initial phase of the punch the movement action became from the contractions of the functional ratio of IR ECC/ER CON which is the acceleration and the next phase with the deceleration ratio of ER ECC/IR CON which is the comeback of the punch. Thus, the importance of the training of rotator muscles was highlighted using an optimal program of shoulder exercises for the evaluation, prevention, and rehabilitation and strength conditioning (
A limitation of the study was that it was conducted in the preparation period of the training year. Muscle strength increases during preparation (
Boxers in the pre-season had normal myodynamic BL ratios on the rotators of shoulders but were at injury risk at the UL ratios. This observation highlighted the importance of these muscles for training and performance, with the reduction of deficit arises of the neuromuscular adaptations of strength training and the importance of the evaluation of asymmetries in athletes as according to the motor each sport templates which is an adaptive necessity for better performance and the prevention of injury. Further studies in higher speeds 240, 300°/s and in women athletes are necessary to confirm the contribution of the rotators muscles to performance and to the healthy exercise.
IT performed the laboratory analyses, the statistical analyses, and drafted the manuscript. PN, AT, AS, TR, and BK helped in drafting the manuscript.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We thank Mr. Dimitrios Skordis and the Physiotherapy and rehabilitation center,