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Have you noticed that your weight is going up while you increase your strength training workouts? That number on the scale simply means you weigh more or you weigh less. It is not a readout on the intensity of your workouts, your body composition, or your level of fitness. There are several different reasons that you may notice an increase in weight when you begin strength training. In some cases, the higher number means that you are making progress. Weight training can cause weight gain due to an increase in muscle mass. If you strength train regularly and improve your fitness level, your weight on the scale may increase while your body fat percentage decreases. Muscle is denser than fat and takes up more space. This switch in body composition happens over months. You can confirm that it is happening by looking in the mirror at the changes in your body, trying on that pair of jeans you have owned since before you started your weight training program, or using a simple body fat percentage calculator. If your body fat percentage shows more muscle and less fat, then that is the change you are looking for. If your jeans are baggy or loose, or if you look in the mirror and a more muscular person is staring back at you, then your strength training efforts could be causing a bit of an uptick on the scale. Breathe easy, you are making positive changes in your health, body definition, and physical appearance. Water can change your weight. Ever notice you weigh less after a sweaty workout session? That loss of sweat can cause a decrease on the scale, just as a salty dinner can cause your weight to increase because your body is retaining water. Your weight can fluctuate due to your water retention versus water loss, and it is not related to your strength training at all. No matter what, stay hydrated all day. Stress can cause weight gain. When you are under stress from tough workouts or a tough day at the office your body produces the stress hormone cortisol. More cortisol released in the body can cause fluid retention. Lack of sleep due to stress can make you hungrier too, and you may eat more than you normally do. Make sure you plan some downtime to do the things that recharge you mentally and physically to alleviate some stress. Be sure to take a recovery day during your workout week, so you are not over-exerting your body. A change in your diet may affect the number on the scale. Do not use workouts as your green light to eat whatever you want. Sometimes when you have an intense sweat session or you push yourself in a new way, you can look to food as a reward for a hard workout completed.
Your body does need fuel (especially when you train), but an intense workout is not a license to eat whatever and as much as you want. Eat clean and watch your portions—even when you are working out hard. There are many factors that can change your weight such as hormones, stress, sodium intake, water consumption, and your body getting too accustomed to the same old workout. These variables can make your weight can go up and down. Keep making healthy decisions and use tools other than your scale to track your progress such as using a tape measure to track your chest, waist, hip, and leg circumference. Think of strength training as your long-term solution to weight loss instead of fearing that it will cause weight gain. Strength training offers many health benefits, including an increase in the number of calories burned. The more muscle you have in your body, the more calories you burn through every single day. So strength training is the best way to gain muscle mass and lose body fat.
“Muscle tissue burns more calories than fat tissue, and building muscles costs a lot of energy. As you increase the amount of muscle you have, you will also increase your resting metabolic rate.” —American Council on Exercise If you gain a little bit as you invest in regular strength training, do not panic. You are training your body to be a calorie-burning machine. Check your body composition or take a good look in your full-length mirror. You will see that your body is changing for the better. Display options Format AbstractPubMedPMID
Key points: Previous studies have indicated that several weeks of strength training is sufficient to elicit significant adaptations in the neural drive sent to the muscles. There are few data, however, on the changes elicited by strength training in the recruitment and rate coding of motor units during voluntary contractions. We show for the first time that the discharge characteristics of motor units in the tibialis anterior muscle tracked across the intervention are changed by 4 weeks of strength training with isometric voluntary contractions. The specific adaptations included significant increases in motor unit discharge rate, decreases in the recruitment-threshold force of motor units and a similar input-output gain of the motor neurons. The findings suggest that the adaptations in motor unit function may be attributable to changes in synaptic input to the motor neuron pool or to adaptations in intrinsic motor neuron properties. Abstract: The strength of a muscle typically begins to increase after only a few sessions of strength training. This increase is usually attributed to changes in the neural drive to muscle as a result of adaptations at the cortical or spinal level. We investigated the change in the discharge characteristics of large populations of longitudinally tracked motor units in tibialis anterior before and after 4 weeks of strength training the ankle-dorsiflexor muscles with isometric contractions. The adaptations exhibited by 14 individuals were compared with 14 control subjects. High-density electromyogram grids with 128 electrodes recorded the myoelectric activity during isometric ramp contractions to the target forces of 35%, 50% and 70% of maximal voluntary force. The motor unit recruitment and derecruitment thresholds, discharge rate, interspike intervals and estimates of synaptic inputs to motor neurons were assessed. The normalized recruitment-threshold forces of the motor units were decreased after strength training (P < 0.05). Moreover, discharge rate increased by 3.3 ± 2.5 pps (average across subjects and motor units) during the plateau phase of the submaximal isometric contractions (P < 0.001). Discharge rates at recruitment and derecruitment were not modified by training (P < 0.05). The association between force and motor unit discharge rate during the ramp-phase of the contractions was also not altered by training (P < 0.05). These results demonstrate for the first time that the increase in muscle force after 4 weeks of strength training is the result of an increase in motor neuron output from the spinal cord to the muscle. Keywords: Decomposition; EMG; Motor Units; Neural Adaptations; Resistance Training. © 2019 The Authors. The Journal of Physiology © 2019 The Physiological Society.
Figure 1. Experimental setup overview and motor… Figure 1. Experimental setup overview and motor unit decomposition A , two high‐density grids of… Figure 1. Experimental setup overview and motor unit decompositionA, two high‐density grids of electrodes placed over the tibialis anterior muscle (64 electrodes in each grid). B, representative trapezoidal ramp isometric contraction (force signal in black) with the simultaneous recorded high‐density electromyogram (monopolar recordings). Only one column of the grid (indicated with a dashed rectangle) is shown. C, an example of two motor unit action potentials extracted from the decomposition analysis. The location of the motor action potential is indicated by the dashed rectangle.
Figure 2. Number of identified motor units… Figure 2. Number of identified motor units as a function of recruitment threshold and target… Swarm plots of all the motor units identified for the control (A) and strength‐training (B) groups. The blue and red dots represent the motor unit recruitment thresholds (y‐axis) identified at the start and end of the intervention, respectively. The three target forces (35%, 50% and 70% of maximal voluntary force, MVF) are shown on the x‐axis. C and D, the average recruitment thresholds of the motor units that were tracked at the start and the end of the intervention, for both the control (C) and strength‐training (D) groups. * P < 0.05, *** P < 0.001.
Figure 3. Discharge times for motor units… Figure 3. Discharge times for motor units across the 4‐week intervention Discharge times for motor… Figure 3. Discharge times for motor units across the 4‐week interventionDischarge times for motor units that were tracked across the 4 week intervention in one subject from the Control group (left column) and one subject from the strength‐training group (right column). A and B, force exerted by the ankle dorsiflexors (grey and dark lines, before and after the intervention, respectively) during an isometric contraction up to 35% of maximal voluntary force. Each colour represents the discharge times of the same motor unit across sessions. Note the preservation of recruitment and decruitment order across session for the tracked units. C and D, instantaneous discharge rates for two representative motor units from the two subjects during the trapezoidal contraction. E and F, motor unit action potentials obtained from bipolar high‐density EMG signals corresponding to the motor units displayed in (C) and (D) (#1 and #11 for the control subject and #2 and #10 for the subject in the strength‐training group). The columns and rows represent the dimensions of the high‐density electrode. The motor unit signatures were extracted by spike‐triggered averaging from the discharge times shown in (A) and (B). Each trace comprising two waveforms, one from before the intervention (blue) and one after the intervention (red). The two lines are almost indistinguishable, which results in a high two‐dimensional correlation coefficients (r) both before and after the 4 week intervention.
Figure 4. Scatter plots of the recruitment… Figure 4. Scatter plots of the recruitment thresholds Scatter plots of the recruitment thresholds for… Figure 4. Scatter plots of the recruitment thresholdsScatter plots of the recruitment thresholds for the same motor units in each participant in the control (asterisks) and strength‐training groups (intervention, filled circles). Each subject is indicated by a different colour. The recruitment thresholds are shown before (on the ordinate) and after (on the abscissa) the intervention. A and B, upper: absolute recruitment thresholds (N) for all the identified motor units. C and D, lower: normalized recruitment threshold expressed as a percentage of maximal voluntary force (% MVF). Average values for absolute (E) and normalized (F) motor unit recruitment thresholds across all motor units for each subject for the control and strength‐training groups (grey bars). * P < 0.05, ** P < 0.01. Data are reported as the mean ± SD.
Figure 5. Scatter plots of the derecruitment… Figure 5. Scatter plots of the derecruitment thresholds Scatter plots of the derecruitment thresholds for… Figure 5. Scatter plots of the derecruitment thresholdsScatter plots of the derecruitment thresholds for the same motor units in each participant in the control (asterisks) and strength‐training groups (intervention, filled circles). Each subject is indicated by a different colour. The derecruitment thresholds are shown before (on the ordinate) and after (on the abscissa) the intervention. A and B, upper: absolute derecruitment thresholds (N) for all the identified motor units. C and D, lower: normalized derecruitment threshold expressed as a percentage of maximal voluntary force (% MVF). Average values for absolute (E) and normalized (F) motor unit derecruitment thresholds across all motor units for each subject for the control and strength‐training groups (grey bars). * P < 0.05. Data are reported as the mean ± SD.
Figure 6. Changes in motor unit discharge… Figure 6. Changes in motor unit discharge rate Scatter plots of the discharge rates for… Figure 6. Changes in motor unit discharge rateScatter plots of the discharge rates for the same motor units in each participant in the control (A, asterisks) and strength‐training groups (B, intervention, filled circles). Each subject is indicated by a different colour in all panels. C, average discharge rate at recruitment (first three interspike intervals) for each subject and group (grey bars for the strength‐training group). D, average discharge rate (first nine interspike intervals) during the plateau phase of the trapezoidal contraction. There was a significant increase in discharge rate during the plateau after strength training. E, average discharge rate (last three interspike intervals) at derecruitment for each subject in the control and strength‐training groups. Motor unit discharge rates are shown at recruitment (F), plateau phase (G) and at derecruitment (H) for all the unmatched units. Similar to the matched units, the discharge rate for the strength‐training group increased only during the plateau phase of the ramp contraction. Data are reported as the mean ± SD. *** P < 0.001.
Figure 7. The difference in motor unit… Figure 7. The difference in motor unit discharge rate (before and after 4 weeks of… Each data point indicates one motor unit at one of the three target forces (35%, 50% and 70% MVF). The motor unit discharge rate was obtained by averaging the first nine interspike intervals at the start of the plateau phase.
Figure 8. Distribution of motor unit interspike… Figure 8. Distribution of motor unit interspike intervals Histograms of motor unit interspike intervals (ISIs)… Figure 8. Distribution of motor unit interspike intervalsHistograms of motor unit interspike intervals (ISIs) are shown for the control (A) and strength‐training (B) groups at the start (red) and end (blue) of the intervention. C, ISI histograms for the three target forces (35%, 50% and 70% MVF) for the strength‐training group. D, ISI histograms for eight motor units in one representative subject in the strength‐training group.
Figure 9. Scatter graphs of the differences… Figure 9. Scatter graphs of the differences in force and discharge rate between the plateau… Each circle represents one motor unit. A and B, absolute recruitment thresholds for the two groups. C and D, relative recruitment threshold for the two groups. E, rate of change in absolute (pps/N) and relative (F, pps/% MVF) discharge rate for each subject (open bar for the controls). Data are reported as the mean ± SD.
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When beginning strength training Which of the following is the cause of the first gains in strength?
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